Remote Method Invocation (RMI) allows Java objects to invoke methods on remote Java objects located on other hosts or machines. RMI uses stubs and skeletons as proxies to make remote calls appear local. The stubs act as local representatives for remote objects, while skeletons on the remote host receive the calls and forward them to the actual remote objects. RMI handles object serialization and deserialization to transfer objects between clients and servers.
RMI allows Java objects to run remotely by making remote method calls appear as local method calls. The document discusses RMI concepts like remote objects, stubs, skeletons, and registries. It provides examples of defining remote interfaces, implementing remote objects, registering objects, and making remote calls from a client.
RMI allows Java objects to invoke methods on remote Java objects located in another Java Virtual Machine. It handles marshaling parameters, transportation between client and server, and unmarshaling results. To create an RMI application, interfaces define remote services, servers implement interfaces and register with the RMI registry, and clients lookup services and invoke remote methods similarly to local calls. Stub and skeleton objects handle communication between remote VMs.
this document provide the information about the RMI(Remote Method Invocation).in this document cover topic like architecture of RMI,stub, skeleton and how work RMI application.
This document defines and describes Java RMI (Remote Method Invocation). RMI allows a Java program running on one JVM to invoke methods on another JVM, enabling client-server programming. It discusses the goals of RMI including minimizing differences between local and remote objects. The architecture of RMI including layers for the application, proxies, remote references, and transport is described. Finally, it compares RMI to other remote object technologies like CORBA.
This document provides an overview of Java RMI (Remote Method Invocation), which allows objects to invoke methods on remote Java objects located elsewhere on a network. Key points:
- RMI allows one JVM to communicate with another and invoke methods remotely as if they were local.
- Remote interfaces define the methods that can be invoked remotely. The interface is shared between client and server code.
- When a remote method is invoked, a stub on the client side packages the parameters and sends them to the server, where the method is executed and results returned.
- Typical RMI applications have a server that creates remote objects and a client that looks them up and invokes their methods. The client interacts
This document provides an overview of how Java RMI (Remote Method Invocation) works. It discusses the key RMI classes and interfaces, the general architecture involving remote objects, stubs, skeletons and the registry. It also demonstrates building the required classes for a simple weather server example - the remote interface, remote object implementation, server and client. The document walks through compiling and running the weather server to showcase a basic RMI application.
Overview of Java RMI remoting.
RMI is a lightweight Java technology that provides access to remote methods, similar to RPC, but object-oriented. RMI basically provides remote object access for a client and object registration for servers.
RMI is both a Java API (java.rmi.* package) as well as a transport protocol definition for transporting RMI calls through a network.
RMI is a Java technology since it requires that client and server objects run in a JVM (Java Virtual Machine). By using IIOP as transport protocol, however, it is possible to connect RMI-clients to non-Java server objects (e.g. CORBA).
RMI defines the elements client, server, RMI registry where servers register their services and possibly a plain vanilla web server that can be used by clients to dynamically load object classes to access servers.
Remote Method Invocation (RMI) allows objects within one Java Virtual Machine to invoke methods on objects residing in a separate JVM. RMI uses stub and skeleton layers along with remote references to enable remote communication. The RMI architecture consists of three layers - stub/skeleton, remote reference, and transport layers. RMI provides packages for remote interfaces, object registration and lookup, and client/server support. Developing RMI involves implementing remote interfaces, generating stubs and skeletons, registering objects, and making remote calls via stubs from clients.
RMI allows Java objects to run remotely by making remote method calls appear as local method calls. The document discusses RMI concepts like remote objects, stubs, skeletons, and registries. It provides examples of defining remote interfaces, implementing remote objects, registering objects, and making remote calls from a client.
RMI allows Java objects to invoke methods on remote Java objects located in another Java Virtual Machine. It handles marshaling parameters, transportation between client and server, and unmarshaling results. To create an RMI application, interfaces define remote services, servers implement interfaces and register with the RMI registry, and clients lookup services and invoke remote methods similarly to local calls. Stub and skeleton objects handle communication between remote VMs.
this document provide the information about the RMI(Remote Method Invocation).in this document cover topic like architecture of RMI,stub, skeleton and how work RMI application.
This document defines and describes Java RMI (Remote Method Invocation). RMI allows a Java program running on one JVM to invoke methods on another JVM, enabling client-server programming. It discusses the goals of RMI including minimizing differences between local and remote objects. The architecture of RMI including layers for the application, proxies, remote references, and transport is described. Finally, it compares RMI to other remote object technologies like CORBA.
This document provides an overview of Java RMI (Remote Method Invocation), which allows objects to invoke methods on remote Java objects located elsewhere on a network. Key points:
- RMI allows one JVM to communicate with another and invoke methods remotely as if they were local.
- Remote interfaces define the methods that can be invoked remotely. The interface is shared between client and server code.
- When a remote method is invoked, a stub on the client side packages the parameters and sends them to the server, where the method is executed and results returned.
- Typical RMI applications have a server that creates remote objects and a client that looks them up and invokes their methods. The client interacts
This document provides an overview of how Java RMI (Remote Method Invocation) works. It discusses the key RMI classes and interfaces, the general architecture involving remote objects, stubs, skeletons and the registry. It also demonstrates building the required classes for a simple weather server example - the remote interface, remote object implementation, server and client. The document walks through compiling and running the weather server to showcase a basic RMI application.
Overview of Java RMI remoting.
RMI is a lightweight Java technology that provides access to remote methods, similar to RPC, but object-oriented. RMI basically provides remote object access for a client and object registration for servers.
RMI is both a Java API (java.rmi.* package) as well as a transport protocol definition for transporting RMI calls through a network.
RMI is a Java technology since it requires that client and server objects run in a JVM (Java Virtual Machine). By using IIOP as transport protocol, however, it is possible to connect RMI-clients to non-Java server objects (e.g. CORBA).
RMI defines the elements client, server, RMI registry where servers register their services and possibly a plain vanilla web server that can be used by clients to dynamically load object classes to access servers.
Remote Method Invocation (RMI) allows objects within one Java Virtual Machine to invoke methods on objects residing in a separate JVM. RMI uses stub and skeleton layers along with remote references to enable remote communication. The RMI architecture consists of three layers - stub/skeleton, remote reference, and transport layers. RMI provides packages for remote interfaces, object registration and lookup, and client/server support. Developing RMI involves implementing remote interfaces, generating stubs and skeletons, registering objects, and making remote calls via stubs from clients.
This document provides an overview of Remote Method Invocation (RMI) in Java. RMI allows programs to call methods on remote Java objects living in another Java Virtual Machine. It describes the key components of RMI including remote interfaces, remote objects, stubs, skeletons and the RMI architecture. It also provides a short example of an RMI application that calculates the sum of two integers by invoking a remote method from the client to the server.
The document describes the RMI architecture which allows objects in one Java virtual machine to invoke methods on objects residing in another Java VM. It discusses key concepts like stubs and skeletons which act as proxies, the remote reference layer for method invocation, and the RMI registry for lookup remote objects by name. It also provides steps to create a basic RMI application including defining the interface, implementing it, creating the server and client code, and running the application.
This document provides an overview of Remote Method Invocation (RMI) in Java. RMI allows objects running in one Java Virtual Machine (JVM) to invoke methods on objects running in another JVM. It describes the RMI process which involves defining a remote interface, compiling the remote object, and making the object accessible over the network. The client locates the remote object and invokes its methods similarly to a local object. The server implements the remote interface and provides the business logic to fulfill client requests.
This document discusses Remote Method Invocation (RMI) in Java. It explains that RMI allows a Java object to invoke methods on an object running on another machine, enabling remote communication between Java programs. It then describes the basic concepts of an RMI application including client/server architecture using stub and skeleton objects. Finally, it outlines the steps to implement a simple RMI application with an interface, client, and server classes.
Recently The Java Remote Method Invocation (RMI) system allows an object running in one Java virtual machine to invoke methods on an object running in another Java virtual machine. RMI provides for remote communication between programs written in the Java programming language.
RMI allows Java objects to call methods on other Java objects running in a different JVM. It works by passing object references between JVMs using marshaling and unmarshaling. Developing an RMI application involves defining a remote interface, implementing that interface in a class, running an RMI registry, starting the server, and having the client lookup and invoke methods on remote objects.
The document discusses Java Remote Method Invocation (RMI), which allows remote method calls between Java programs. RMI provides a thin client that maximizes hardware investments. It requires objects to be serializable and looked up from a registry. The RMI architecture has four layers - the application layer containing client and server logic, a proxy layer with stubs and skeletons, a transport layer managing connections, and a remote reference layer managing references. Key RMI components are the server containing remote objects, the client invoking methods, and the registry containing object references.
This document provides an overview of Java Remote Method Invocation (RMI) technology. It discusses that RMI allows applications to invoke methods on remote Java objects, hiding the underlying socket-level communication details. It describes the key components of RMI - the client, server, and RMI registry which maintains references to remote objects. It then presents a simple example to demonstrate implementing and using an RMI application for mathematical operations, including writing the service interface, server implementation, and client. Finally, it discusses strengths and weaknesses of RMI and compares it to another distributed object technology, CORBA.
This document discusses Java Remote Method Invocation (RMI), which allows Java objects to invoke methods on other Java objects running in another Java Virtual Machine (JVM). It describes how RMI works using a client-server model, with an interface defining remote methods, an implementation class on the server exporting objects, and clients looking them up by name. It provides code examples of an RMI server interface, implementation class, and client class, along with steps for compiling, running the rmiregistry, and potential error sources.
This document discusses distributed programming with Java RMI. It explains the key components of client-server systems and different distributed computing models like DCE, DCOM, CORBA, and Java RMI. It then describes how Java RMI works, the packages involved, and provides steps to implement a basic RMI application with a remote interface, server implementation, and client.
RMI allows for remote method invocation, making remote objects appear local to clients. It handles threading, sockets, object marshalling between client and server JVMs. The client looks up remote objects in the RMI registry and calls methods which are executed on server object skeletons. Return values pass through stubs back to the client. Advantages include automatic threading and marshalling, dynamic class loading. Disadvantages are that RMI only works with Java and security must be closely monitored.
The document discusses Remote Method Invocation (RMI) in Java. RMI allows objects running in one Java virtual machine to invoke methods on objects running in another Java VM. It has four layers: application layer, proxy layer, remote reference layer, and transport layer. The RMI architecture contains an RMI server, RMI client, and RMI registry. The server creates remote objects and registers them with the registry. The client looks up remote objects by name in the registry and invokes methods on them.
This Presentation shows the working of Java RMI technology, it's advantage over RPC, it's class hierarchy API and finally implementation of Factorial program using Java RMI.
Remote Method Invocation, Distributed Programming in java, Java Distributed Programming, Network Programming in JAVA, Core Java, Introduction to RMI, Getting Started with RMI, Getting Started with Remote Method Invocation, Distributed Programming, Java, J2SE
This document provides an overview of RMI architecture and how to create an RMI application. It discusses that RMI allows invoking methods on remote objects and facilitates communication between distributed objects. It describes local vs remote objects, the RMI registry for registering and looking up remote objects. It outlines the steps to create an RMI application including defining the server interface, implementing the server, registering the server object, and developing the client program.
This document provides an overview of Java Remote Method Invocation (RMI). It discusses the historical background and related technologies like RPC and CORBA. The document describes the layered architecture of RMI including the application, interface, reference, and transport layers. It also explains the working principles of RMI with client/server communication and object serialization. An example RMI application is demonstrated involving writing interfaces and classes, deploying the server, and accessing services from the client. Strengths and weaknesses of RMI are analyzed in comparison to CORBA. The document is intended as a tutorial on building distributed applications with Java RMI.
This document provides an introduction and overview of Remote Method Invocation (RMI) in Java. It describes building a simple client-server application using RMI that allows a client to invoke methods on a Java object running on a remote server machine. The application involves defining a remote interface, implementing that interface on the server, generating stubs and skeletons, running an RMI registry on the server, and having the client lookup and invoke methods on the remote object.
- Ravi Tuppad is a qualified professional with over 2 years of experience developing web and mobile applications using technologies like PHP, HTML5, CSS3, JavaScript, and Android SDK.
- He has strong experience in web design, Android app development, and has worked on projects involving virtual labs, e-learning applications, and video monitoring.
- His skills include web design frameworks like Bootstrap and CakePHP, version control with Git, and debugging. He is proficient in languages like PHP, Java, and technologies like MySQL, Android Studio, and PhoneGap.
RMI (Remote Method Invocation) allows objects to reside remotely and have their methods invoked from another Java Virtual Machine. An RMI application typically has a server that creates remote objects and makes them accessible, and a client that obtains references to remote objects and invokes their methods. RMI handles communication between remote objects, making remote calls appear similar to local method calls. It also loads class definitions as needed to allow objects to be passed between VMs.
This document provides information about implementing and using Remote Method Invocation (RMI) in Java. It describes how RMI allows objects in one Java Virtual Machine (JVM) to invoke methods on objects residing in another JVM, even on different computers. It discusses how RMI handles class loading and updates dynamically. It then explains how RMI works under the hood using stub and skeleton objects to marshal parameters and return values across the network. The document provides steps for writing an RMI program and includes a full code example of an RMI service that calculates powers and its client.
This document provides an overview of Remote Method Invocation (RMI) in Java. RMI allows programs to call methods on remote Java objects living in another Java Virtual Machine. It describes the key components of RMI including remote interfaces, remote objects, stubs, skeletons and the RMI architecture. It also provides a short example of an RMI application that calculates the sum of two integers by invoking a remote method from the client to the server.
The document describes the RMI architecture which allows objects in one Java virtual machine to invoke methods on objects residing in another Java VM. It discusses key concepts like stubs and skeletons which act as proxies, the remote reference layer for method invocation, and the RMI registry for lookup remote objects by name. It also provides steps to create a basic RMI application including defining the interface, implementing it, creating the server and client code, and running the application.
This document provides an overview of Remote Method Invocation (RMI) in Java. RMI allows objects running in one Java Virtual Machine (JVM) to invoke methods on objects running in another JVM. It describes the RMI process which involves defining a remote interface, compiling the remote object, and making the object accessible over the network. The client locates the remote object and invokes its methods similarly to a local object. The server implements the remote interface and provides the business logic to fulfill client requests.
This document discusses Remote Method Invocation (RMI) in Java. It explains that RMI allows a Java object to invoke methods on an object running on another machine, enabling remote communication between Java programs. It then describes the basic concepts of an RMI application including client/server architecture using stub and skeleton objects. Finally, it outlines the steps to implement a simple RMI application with an interface, client, and server classes.
Recently The Java Remote Method Invocation (RMI) system allows an object running in one Java virtual machine to invoke methods on an object running in another Java virtual machine. RMI provides for remote communication between programs written in the Java programming language.
RMI allows Java objects to call methods on other Java objects running in a different JVM. It works by passing object references between JVMs using marshaling and unmarshaling. Developing an RMI application involves defining a remote interface, implementing that interface in a class, running an RMI registry, starting the server, and having the client lookup and invoke methods on remote objects.
The document discusses Java Remote Method Invocation (RMI), which allows remote method calls between Java programs. RMI provides a thin client that maximizes hardware investments. It requires objects to be serializable and looked up from a registry. The RMI architecture has four layers - the application layer containing client and server logic, a proxy layer with stubs and skeletons, a transport layer managing connections, and a remote reference layer managing references. Key RMI components are the server containing remote objects, the client invoking methods, and the registry containing object references.
This document provides an overview of Java Remote Method Invocation (RMI) technology. It discusses that RMI allows applications to invoke methods on remote Java objects, hiding the underlying socket-level communication details. It describes the key components of RMI - the client, server, and RMI registry which maintains references to remote objects. It then presents a simple example to demonstrate implementing and using an RMI application for mathematical operations, including writing the service interface, server implementation, and client. Finally, it discusses strengths and weaknesses of RMI and compares it to another distributed object technology, CORBA.
This document discusses Java Remote Method Invocation (RMI), which allows Java objects to invoke methods on other Java objects running in another Java Virtual Machine (JVM). It describes how RMI works using a client-server model, with an interface defining remote methods, an implementation class on the server exporting objects, and clients looking them up by name. It provides code examples of an RMI server interface, implementation class, and client class, along with steps for compiling, running the rmiregistry, and potential error sources.
This document discusses distributed programming with Java RMI. It explains the key components of client-server systems and different distributed computing models like DCE, DCOM, CORBA, and Java RMI. It then describes how Java RMI works, the packages involved, and provides steps to implement a basic RMI application with a remote interface, server implementation, and client.
RMI allows for remote method invocation, making remote objects appear local to clients. It handles threading, sockets, object marshalling between client and server JVMs. The client looks up remote objects in the RMI registry and calls methods which are executed on server object skeletons. Return values pass through stubs back to the client. Advantages include automatic threading and marshalling, dynamic class loading. Disadvantages are that RMI only works with Java and security must be closely monitored.
The document discusses Remote Method Invocation (RMI) in Java. RMI allows objects running in one Java virtual machine to invoke methods on objects running in another Java VM. It has four layers: application layer, proxy layer, remote reference layer, and transport layer. The RMI architecture contains an RMI server, RMI client, and RMI registry. The server creates remote objects and registers them with the registry. The client looks up remote objects by name in the registry and invokes methods on them.
This Presentation shows the working of Java RMI technology, it's advantage over RPC, it's class hierarchy API and finally implementation of Factorial program using Java RMI.
Remote Method Invocation, Distributed Programming in java, Java Distributed Programming, Network Programming in JAVA, Core Java, Introduction to RMI, Getting Started with RMI, Getting Started with Remote Method Invocation, Distributed Programming, Java, J2SE
This document provides an overview of RMI architecture and how to create an RMI application. It discusses that RMI allows invoking methods on remote objects and facilitates communication between distributed objects. It describes local vs remote objects, the RMI registry for registering and looking up remote objects. It outlines the steps to create an RMI application including defining the server interface, implementing the server, registering the server object, and developing the client program.
This document provides an overview of Java Remote Method Invocation (RMI). It discusses the historical background and related technologies like RPC and CORBA. The document describes the layered architecture of RMI including the application, interface, reference, and transport layers. It also explains the working principles of RMI with client/server communication and object serialization. An example RMI application is demonstrated involving writing interfaces and classes, deploying the server, and accessing services from the client. Strengths and weaknesses of RMI are analyzed in comparison to CORBA. The document is intended as a tutorial on building distributed applications with Java RMI.
This document provides an introduction and overview of Remote Method Invocation (RMI) in Java. It describes building a simple client-server application using RMI that allows a client to invoke methods on a Java object running on a remote server machine. The application involves defining a remote interface, implementing that interface on the server, generating stubs and skeletons, running an RMI registry on the server, and having the client lookup and invoke methods on the remote object.
- Ravi Tuppad is a qualified professional with over 2 years of experience developing web and mobile applications using technologies like PHP, HTML5, CSS3, JavaScript, and Android SDK.
- He has strong experience in web design, Android app development, and has worked on projects involving virtual labs, e-learning applications, and video monitoring.
- His skills include web design frameworks like Bootstrap and CakePHP, version control with Git, and debugging. He is proficient in languages like PHP, Java, and technologies like MySQL, Android Studio, and PhoneGap.
RMI (Remote Method Invocation) allows objects to reside remotely and have their methods invoked from another Java Virtual Machine. An RMI application typically has a server that creates remote objects and makes them accessible, and a client that obtains references to remote objects and invokes their methods. RMI handles communication between remote objects, making remote calls appear similar to local method calls. It also loads class definitions as needed to allow objects to be passed between VMs.
This document provides information about implementing and using Remote Method Invocation (RMI) in Java. It describes how RMI allows objects in one Java Virtual Machine (JVM) to invoke methods on objects residing in another JVM, even on different computers. It discusses how RMI handles class loading and updates dynamically. It then explains how RMI works under the hood using stub and skeleton objects to marshal parameters and return values across the network. The document provides steps for writing an RMI program and includes a full code example of an RMI service that calculates powers and its client.
This document discusses advanced Java programming topics related to networking. It covers network basics like TCP, UDP, IP addresses and ports. It then discusses client-server architecture and how sockets are used for communication. It explains how to create server and client sockets and handle multiple clients. It also discusses how to send and receive objects and provides an overview of the Java Mail API for sending emails.
1. Sockets provide a connection between client and server programs that allows them to communicate over a network. A socket is bound to each end of the connection.
2. The Socket class implements client sockets and allows a client program to connect to a server, send and receive data, and close the connection. The ServerSocket class allows a server program to listen for connections on a port and accept sockets from clients.
3. When a client connects to a server, the server accepts the connection using ServerSocket and returns a Socket. The client and server can then communicate by getting input and output streams from the socket to send data over the connection according to the network protocol.
JDBC allows Java programs to execute SQL statements. It includes interfaces and classes that provide methods for connecting to a database, executing queries, processing result sets, and managing transactions. The key components of JDBC are the JDBC API, driver manager, drivers, and Java SQL package. There are four types of JDBC drivers: Type 1 uses JDBC-ODBC bridge, Type 2 uses a native database API, Type 3 uses a network protocol, and Type 4 communicates directly with a database via its network protocol. Creating a database connection in JDBC involves loading the driver, getting a connection, creating statements, executing queries, and closing resources.
A Java servlet is a server-side program that processes requests from clients. Servlets offer improved performance over CGI by remaining loaded in memory between requests. The Servlet API defines interfaces and classes for writing servlets, including Servlet, ServletRequest, and ServletResponse. Tomcat is a popular servlet container for developing and testing servlets. A basic "Hello World" servlet uses the Servlet API to write a response containing HTML.
Java servlets are small Java programs that run on a web server and respond to requests from a client browser. Servlets receive HTTP requests from the browser, generate dynamic content, and return HTTP responses. When the server first loads a servlet, it calls the servlet's init() method to initialize it. The servlet then handles requests via its service() method, building responses using server resources. When the server removes a servlet, it calls the servlet's destroy() method to perform cleanup. Servlets allow dynamic web content and interaction between clients and server resources like databases.
RMI allows Java objects to make remote calls to methods on other Java objects located in different JVMs. The document discusses how to create remote objects that implement remote interfaces, generate stubs and skeletons, and look up and invoke methods on remote objects. It provides an example "Hello World" RMI application to demonstrate the basic steps of developing and running an RMI client and server.
The document discusses Remote Method Invocation (RMI) in Java. RMI allows objects to invoke methods on objects residing in another Java Virtual Machine (JVM). It uses stub and skeleton objects to enable remote communication between applications. The stub acts as a client-side proxy and the skeleton receives incoming requests on the server-side. The document provides an example to demonstrate creating a remote interface, implementing it, compiling the stub and skeleton, starting the registry, and running a client and server application to invoke the remote method.
The document describes developing a distributed RMI application with a database. It involves:
1) Creating a remote interface and implementation class to access the database.
2) Compiling the class and starting the RMI registry.
3) Creating and running a server that binds the remote object.
4) Creating and running a client that looks up the remote object and invokes its methods.
This document discusses Remote Method Invocation (RMI) in Java. RMI allows objects to invoke methods on remote objects running in different Java Virtual Machines. It uses stub and skeleton objects for communication. The stub resides on the client-side and acts as a proxy for the remote object, marshalling method calls and results. The skeleton resides on the server-side and unmarshalls incoming method calls, invokes the corresponding method on the remote object, and marshalls the result back to the client. An example Java implementation is provided demonstrating how to define a remote interface, create a server object that implements it, register it with the RMI registry, and have a client lookup and invoke methods on the remote
Remote Method Invocation (RMI) allows developers to invoke methods on remote Java objects. RMI handles the details of communication between remote objects transparently so that remote calls appear as local method calls. The RMI registry provides naming services that allow clients to lookup remote objects by name, simplifying the specification of remote objects' locations. Developers define interfaces for remote objects, generate stubs and skeletons, implement remote objects, register them with the RMI registry, and have clients lookup and invoke methods on remote objects.
This document provides an overview of Java RMI (Remote Method Invocation), which allows objects to invoke methods on remote Java objects located elsewhere on a network. Key points:
- RMI allows one JVM to communicate with another and invoke methods remotely as if they were local.
- Remote interfaces define the methods that can be invoked remotely. The interface is shared between client and server code.
- When a remote method is invoked, a stub on the client side packages the parameters and sends them to the server, where the method is executed and results returned.
- Typical RMI applications have a server that creates remote objects and a client that looks them up and invokes their methods remotely.
If you have an access to an object on a different machine,
you can call methods of the remote object.of course, the method parameters must somehow be shipped to the other machine,the server must be informed to execute the method & the return value must be shipped back.
In RMI, the object whose methods makes the remote call is called the client object. The remote object is called the server object.The computer running the java code that calls the remote method is the client for that call.
The computer hosting the object that processes the call is the server for that call.
The document discusses how to implement callbacks in Java RMI using remote method invocation. It describes defining a listener interface and event source interface, implementing the event source to notify listeners, implementing a listener client, and registering the listener with the event source. It provides code examples for implementing and registering both the event source and listener.
The document discusses how to implement callbacks in Java RMI using remote method invocation. It describes defining a listener interface and event source interface, implementing the event source to notify listeners, implementing a listener client, and registering the listener with the event source. It provides code examples for implementing the event source and listener interfaces, starting the event source server, and having the listener client look up and register with the event source.
The document discusses using remote method invocation (RMI) in Java to implement callbacks. It describes defining a listener interface that other classes can implement to be notified of events. An event source interface is defined to allow listeners to register and receive notifications. The event source is implemented as an RMI server that notifies all registered listeners when temperature changes. A client implements the listener interface and registers with the server to receive remote callbacks of temperature changes.
The document discusses how to implement callbacks in Java RMI using remote method invocation. It describes defining a listener interface and event source interface, implementing the event source to notify listeners, implementing a listener client, and registering the listener with the event source. It provides code examples for implementing the event source and listener interfaces, starting the event source server, and having the listener client look up and register with the event source.
The document discusses how to implement callbacks in Java RMI using remote method invocation. It describes defining a listener interface and event source interface, implementing the event source to notify listeners, implementing a listener client, and registering the listener with the event source. It provides code examples for implementing the event source and listener interfaces, starting the event source server, and having the listener client look up and register with the event source.
This document discusses Remote Method Invocation (RMI) in Java. It describes the basic concepts and architecture of RMI, including how remote objects are represented by stubs and skeletons. It then provides step-by-step instructions for building a simple RMI application with four required classes: an interface for the remote object, the client, the remote object implementation, and the server. It also gives an example of building a more complex RMI application for performing numerical integration remotely.
This document discusses Remote Method Invocation (RMI) in Java. It describes the general RMI architecture involving clients, servers, stubs, and skeletons. It outlines the steps to develop an RMI system, including defining the remote interface, developing the remote object, generating stubs and skeletons, starting the RMI registry, and running the client. Key aspects covered are the stub and skeleton's roles in marshaling and unmarshaling calls and results, as well as using a security policy file to control permissions.
Remote Method Invocation (RMI) allows objects running in one Java virtual machine to invoke methods on objects running in another Java virtual machine. RMI uses object serialization to marshal and unmarshal parameters and supports true object-oriented polymorphism. RMI is implemented using three layers - stub, remote reference, and transport connection layers. The stub and skeleton hide the underlying network implementation details and allow remote objects to be called similar to local objects. Security is an important consideration in RMI and a security manager must be installed and permissions configured to control access to remote objects and classes.
RMI allows objects in one Java Virtual Machine (JVM) to invoke methods on objects residing in another JVM. It uses stub and skeleton objects to enable remote communication between Java programs. The stub on the client side sends a call to the server-side skeleton, which then invokes the actual remote object. The key steps to build an RMI application are: defining the remote interface, implementing it, generating stub and skeleton objects, starting the RMI registry, running the server, and making calls from the client.
Remote Method Invocation (RMI) allows programmers to execute remote functions and calls using the same semantics as local function calls. RMI uses stubs and skeletons, where the stub acts as a proxy for the remote object on the client side and the skeleton receives the calls on the server side. To use RMI, an interface must be defined and implemented on the server, stub and skeleton classes are generated, the remote object is registered with an RMI registry, and then clients can look up and invoke methods on the remote object.
The document discusses socket programming and remote method invocation (RMI). It provides details on socket programming concepts like server sockets, client sockets, and examples of a simple echo server and client. It then covers RMI concepts such as locating and invoking remote objects, writing RMI programs, and using serialization to pass objects between clients and servers.
This document provides code for implementing remote method invocation (RMI) between a client and server in Java. It includes code for the interface, server, and client. The interface defines the remote method. The server implements the interface and exports the remote object. It registers the object with the RMI registry. The client looks up the remote object from the registry and invokes the remote method on the server. The client and server communicate over RMI to call the method remotely.
This document discusses distributed object technologies including CORBA and Java RMI. It provides goals, operations, and properties of distributed objects. It then describes components, interfaces, implementations and usage of Java RMI and CORBA for developing distributed applications using remote objects.
1. Remote Method Invocation (RMI)
Remote Method Invocation (RMI) allows us to get a reference
to an object on a remote host and use it as if it were on our
virtual machine. We can invoke methods on the remote
objects, passing real objects as arguments and getting real
objects as returned values. (Similar to Remote Procedure Call
(RPC) in C).
2. Remote Method Invocation (RMI)
Remote Method Invocation (RMI) allows us to get a reference
to an object on a remote host and use it as if it were on our
virtual machine. We can invoke methods on the remote
objects, passing real objects as arguments and getting real
objects as returned values. (Similar to Remote Procedure Call
(RPC) in C).
RMI uses object serialization, dynamic class loading and
security manager to transport Java classes safely. Thus we
can ship both code and data around the network.
3. Remote Method Invocation (RMI)
Remote Method Invocation (RMI) allows us to get a reference
to an object on a remote host and use it as if it were on our
virtual machine. We can invoke methods on the remote
objects, passing real objects as arguments and getting real
objects as returned values. (Similar to Remote Procedure Call
(RPC) in C).
RMI uses object serialization, dynamic class loading and
security manager to transport Java classes safely. Thus we
can ship both code and data around the network.
Stubs and Skeletons. Stub is the local code that serves as a
proxy for a remote object. The skeleton is another proxy that
lives on the same host as the real object. The skeleton
receives remote method invocations from the stub and passes
them on to the object.
4. Remote Interfaces and Implementations
A remote object implements a special remote interface that specifies which of
the object’s methods can be invoked remotely. The remote interface must
extend the java.rmi.Remote interface. Both the remote object and the stub
implement the remote interface.
public interface MyRemoteObject
extends java.rmi.Remote {
public Widget doSomething() throws java.rmi.RemoteException;
public Widget doSomethingElse() throws java.rmi.RemoteException;
}
5. Remote Interfaces and Implementations
A remote object implements a special remote interface that specifies which of
the object’s methods can be invoked remotely. The remote interface must
extend the java.rmi.Remote interface. Both the remote object and the stub
implement the remote interface.
public interface MyRemoteObject
extends java.rmi.Remote {
public Widget doSomething() throws java.rmi.RemoteException;
public Widget doSomethingElse() throws java.rmi.RemoteException;
}
The actual implementation must extend
java.rmi.server.UnicastRemoteObject. It must also provide a
constructor. This is the RMI equivalent of the Object class.
public class RemoteObjectImpl implements MyRemoteObject
extends java.rmi.server.UnicastRemoteObject {
public RemoteObjectImpl() throws java.rmi.RemoteException {...}
public Widget doSomething() throws java.rmi.RemoteException {...}
public Widget doSomethingElse() throws java.rmi.RemoteException {.
// other non-public methods
}
6. RMI Hello Server
--Hello.java--
public interface Hello extends java.rmi.Remote {
String sayHello() throws java.rmi.RemoteException;
}
--HelloServer.java---
import java.rmi.*;
import java.rmi.registry.*;
import java.rmi.server.UnicastRemoteObject;
public class HelloServer extends UnicastRemoteObject implements Hello
{
private String name;
private static int registryPort = 1099;
public HelloServer(String s) throws RemoteException {
super();
name = s;
}
public String sayHello() throws RemoteException {
return "Hello World!";
}
public static void main(String args[])
{
if (args.length > 0) {
registryPort = Integer.parseInt(args[0]);
}
// Create and install a security manager
System.setSecurityManager(new RMISecurityManager());
try {
Registry registry = LocateRegistry.getRegistry(registryPort);
HelloServer obj = new HelloServer("//HelloServer");
registry.rebind("HelloServer", obj);
System.out.println("HelloServer bound in registry");
} catch (Exception e) {
System.out.println("HelloServer err: " + e.getMessage());
e.printStackTrace();
}
}
}
8. Running the RMI Hello World Example
This example is in the folder rmi-rpc/rmi/ex1-HelloServer. First we need to start up
the rmiregistry. It runs on port 1099 by default. Choose a different port if you want to
run your own copy.
rmiregistry [registryPort] &
Then we start up the server as follows:
java -Djava.security.policy=mysecurity.policy HelloServer &
Here mysecurity.policy is the security policy that is required. Now run the client as
follows:
java HelloClient hostname [registryPort]
Once you are done, kill the server and the rmiregistry as shown below.
killall -9 rmiregistry
fg <Ctrl-C>
9. RMI Hello World example
server machineclient machine
rmiregistry
lookup
sayHello()
sayHello()HelloClient
HelloServer
HelloServer_Stub
JVM
HelloServer_Skel
10. Example 2: RMI Square Server
This example is in the folder rmi-rpc/rmi/ex2-SquareServer
--Square---
public interface Square extends java.rmi.Remote {
long square(long arg) throws java.rmi.RemoteException;
}
This example runs n calls to a remote square method, so that we can time the
responsiveness of remote calls.
11. Example 3: Client Callback
This example is in the folder rmi-rpc/rmi/ex3-Client-Callback
--Request--
// Could hold basic stuff like authentication, time stamps, etc.
public class Request implements java.io.Serializable { }
--WorkRequest.java--
public class WorkRequest extends Request {
public Object execute() { return null; }
}
--WorkListener.java--
public interface WorkListener extends Remote {
public void workCompleted( WorkRequest request, Object result )
throws RemoteException;
}
--StringEnumeration.java--
import java.rmi.*;
public interface StringEnumeration extends Remote {
public boolean hasMoreItems() throws RemoteException;
public String nextItem() throws RemoteException;
}
--Server.java--
import java.util.*;
public interface Server extends java.rmi.Remote {
Date getDate() throws java.rmi.RemoteException;
Object execute( WorkRequest work ) throws java.rmi.RemoteException;
StringEnumeration getList() throws java.rmi.RemoteException;
void asyncExecute( WorkRequest work, WorkListener listener )
throws java.rmi .RemoteException;
}
12. Example 3: Server
import java.rmi.*;
import java.util.*;
public class MyServer
extends java.rmi.server.UnicastRemoteObject implements Server {
public MyServer() throws RemoteException { }
// Implement the Server interface
public Date getDate() throws RemoteException {
return new Date();
}
public Object execute( WorkRequest work ) throws RemoteException {
return work.execute();
}
public StringEnumeration getList() throws RemoteException {
return new StringEnumerator(
new String [] { "Foo", "Bar", "Gee" } );
}
public void asyncExecute( WorkRequest request , WorkListener listener )
throws java.rmi.RemoteException {
Object result = request.execute();
System.out.println("async req");
listener.workCompleted( request, result );
System.out.println("async complete");
}
public static void main(String args[]) {
System.setSecurityManager(new RMISecurityManager());
try {
Server server = new MyServer();
Naming.rebind("NiftyServer", server);
System.out.println("bound");
} catch (java.io.IOException e) {
System.out.println("// Problem registering server");
System.out.println(e);
}
}
}
13. Example 3: RMI Client
import java.rmi.*;
public class MyClient
extends java.rmi.server.UnicastRemoteObject implements WorkListener {
public static void main(String [] args) throws RemoteException {
System.setSecurityManager(new RMISecurityManager());
new MyClient( args[0] );
}
public MyClient(String host) throws RemoteException {
try {
Server server = (Server)Naming.lookup("rmi://"+host+"/NiftyServer");
System.out.println( server.getDate() );
System.out.println( server.execute( new MyCalculation(2)));
StringEnumeration se = server.getList();
while ( se.hasMoreItems() )
System.out.println( se.nextItem() );
server.asyncExecute( new MyCalculation(100), this );
} catch (java.io.IOException e) {
// I/O Error or bad URL
System.out.println(e);
} catch (NotBoundException e) {
// NiftyServer isn’t registered
System.out.println(e);
}
}
public void workCompleted( WorkRequest request, Object result)
throws RemoteException
{
System.out.println("Async work result = " + result);
System.out.flush();
}
}
14. Running the RMI Client-Callback Example
This example is in the folder rmi-rpc/rmi/ex3-Client-Callback. Note that the
client needs a copy of MyServer Stub.class whereas the server needs a copy of
MyCalculation.class and MyClient Stub.class.
rmiregistry [registryPort] &
Then we start up the server as follows:
java -Djava.security.policy=mysecurity.policy HelloServer &
or if running over actual internet use
java -Djava.rmi.server.codebase="http://onyx.boisestate.edu/~amit/rmi/ex3/"
-Djava.security.policy=mysecurity.policy MyServer
Here mysecurity.policy is the security policy that is required. Now run the client
as follows:
java -Djava.security.policy=mysecurity.policy MyClient hostname [registryPort]
Note that since the server calls back the client via RMI, the client also needs to
have a security policy. Once you are done, kill the server and the rmiregistry.
15. Example 4: Load classes over the network
See example in folder rmi-rpc/rmi/ex4-Load-Remote-Class.
import java.rmi.RMISecurityManager;
import java.rmi.server.RMIClassLoader;
import java.net.*;
public class LoadClient
{
public static void main(String[] args)
{
System.setSecurityManager(new RMISecurityManager());
try {
URL url = new URL(args[0]);
Class cl = RMIClassLoader.loadClass(url,"MyClient");
System.out.println(cl);
Runnable client = (Runnable)cl.newInstance();
client.run();
System.exit(0);
} catch (Exception e) {
System.out.println("Exception: " + e.getMessage());
e.printStackTrace();
}
}
}
java LoadClient
http://onyx.boisestate.edu/∼amit/codebase/rmi/ex4/
16. Class Loading in Java
The AppletClassLoader is used to download a Java applet over the
net from the location specified by the codebase attribute on the web
page that contains the <applet> tag. All classes used directly in the
applet are subsequently loaded by the AppletClassLoader.
The default class loader is used to load a class (whose main method
is run by using the java command) from the local CLASSPATH. All
classes used directly in that class are subsequently loaded by the
default class loader from the local CLASSPATH.
17. Class Loading in Java (contd.)
The RMIClassLoader is used to load those classes not directly used by
the client or server application: the stubs and skeletons of remote
objects, and extended classes of arguments and return values to RMI
calls. The RMIClassLoader looks for these classes in the following
locations, in the order listed:
The local CLASSPATH. Classes are always loaded locally if they exist
locally.
18. Class Loading in Java (contd.)
The RMIClassLoader is used to load those classes not directly used by
the client or server application: the stubs and skeletons of remote
objects, and extended classes of arguments and return values to RMI
calls. The RMIClassLoader looks for these classes in the following
locations, in the order listed:
The local CLASSPATH. Classes are always loaded locally if they exist
locally.
For objects (both remote and nonremote) passed as parameters or
return values, the URL encoded in the marshal stream that contains
the serialized object is used to locate the class for the object.
19. Class Loading in Java (contd.)
The RMIClassLoader is used to load those classes not directly used by
the client or server application: the stubs and skeletons of remote
objects, and extended classes of arguments and return values to RMI
calls. The RMIClassLoader looks for these classes in the following
locations, in the order listed:
The local CLASSPATH. Classes are always loaded locally if they exist
locally.
For objects (both remote and nonremote) passed as parameters or
return values, the URL encoded in the marshal stream that contains
the serialized object is used to locate the class for the object.
For stubs and skeletons of remote objects created in the local virtual
machine, the URL specified by the local java.rmi.server.codebase
property is used.
20. Dynamic downloading of classes by the RMI Class Loader
Start up the rmiregistry. Make sure you do not start it from the server
folder. If you do start the rmiregistry and it can find your stub classes in
CLASSPATH, it will not remember that the loaded stub class can be
loaded from your server’s code base, specified by the
java.rmi.server.codebase property when you started up your server
application. Therefore, the rmiregistry will not convey to clients the true
code base associated with the stub class and, consequently, your clients
will not be able to locate and to load the stub class or other server-side
classes.
The server and client machines both need to be running a web server.
The folders containing the server and client code both need to be
accessible via the web.
21. Example 6: Dynamic downloading of classes
See example in the folder rmi-rpc/rmi/ex6-Dynamic-Classloading.
The following shows a sample server start up, where the server is running on onyx.
currdir=‘pwd‘
cd /
rmiregistry &
cd $currdir
java -Djava.rmi.server.codebase="http://onyx.boisestate.edu/~amit/rmi/ex6/"
-Djava.security.policy=mysecurity.policy MyServer
The following shows a sample client start up, where the client is running on the host
cs.
java
-Djava.rmi.server.codebase="http://cs.boisestate.edu/~amit/teaching/555/lab/ex6/"
-Djava.security.policy=mysecurity.policy MyClient onyx
22. RMI and Thread Safety
The default RMI implementation is multi-threaded. So if
multiple clients call the server, all the method invocations can
happen simultaneously, causing race conditions. The same
method may also be run by more than one thread on behalf of
one or more clients. Hence we must write the server to be
thread-safe.
Use the synchronized keyword to ensure thread-safety.
The example rmi-rpc/rmi/ex7-RMI-Thread-Safety
demonstrates the problem and a possible solution.
23. Example 7: RMI Thread Safety
import java.rmi.*;
public interface RMIThreadServer extends Remote {
public void update() throws RemoteException;
public int read() throws RemoteException;
}
24. Example 7 contd.: Server
import ...
public class RMIThreadServerImpl extends UnicastRemoteObject implements RMIThreadServer
{
private volatile int counter = 0;
private final int MAXCOUNT = 900000;
public RMIThreadServerImpl () throws RemoteException {
super();
}
/*public synchronized void update() {*/
public void update() {
int i;
Thread p = Thread.currentThread();
System.out.println("[server] Entering critical section: " + p.getName());
for (i = 0; i < MAXCOUNT; i++)
this.counter++;
for (i = 0; i < MAXCOUNT; i++)
this.counter--;
System.out.println("[server] Leaving critical section: " + p.getName());
}
/*public synchronized int read() {*/
public int read() {
return this.counter;
}
public static void main (String[] args) {
try {
RMIThreadServerImpl localObject = new RMIThreadServerImpl( );
Naming.rebind("//localhost:5130/RMIThreadServer", localObject);
System.err.println("DEBUG: RMIThreadServerImpl RMI listener boundn");
} catch (RemoteException e) {
System.err.println("RemoteException: " + e);
} catch (MalformedURLException e) {
System.err.println("MalformedURLException: " + e);
}
}
}
26. Creating a Asynchronous Server/Client
To convert the Example 3 into a true asynchronous server, we
would need a spawn off a thread for each asynchronous
request that would execute the request and then call the
client back with the result.
On the client side, we need to keep track of number of
asynchronous requests out to the server so the client doesn’t
quit until all the results have come back. Since the client is
also potentially multi-threaded, we will need to use
synchronization.
See example rmi-rpc/rmi/ex5-Asynchronous-Server.
27. Example 5: Asynchronous Server
public class MyServer
extends java.rmi.server.UnicastRemoteObject implements Server
{
...
public void asyncExecute( WorkRequest request , WorkListener listener )
throws java.rmi.RemoteException
{
new AsyncExecuteThread(request, listener).start();
System.out.println("Started thread to execute request.");
}
...
}
class AsyncExecuteThread extends Thread
{
WorkRequest request;
WorkListener listener;
public AsyncExecuteThread(WorkRequest request, WorkListener listener)
{
this.request = request;
this.listener = listener;
}
public void run()
{
try {
Object result = request.execute();
System.out.println("async req");
listener.workCompleted( request, result );
System.out.println("async complete");
} catch (RemoteException e) {
System.out.println("AsyncExecuteThread:"+e);
}
}
}
28. Example 5: Asynchronous Client
public class MyClient extends java.rmi.server.UnicastRemoteObject
implements WorkListener
{
private Semaphore sem;
private static final long serialVersionUID = -6314695118464643327L;
public static void main(String [] args) throws RemoteException
{
System.setSecurityManager(new RMISecurityManager());
new MyClient(args[0]);
}
public MyClient(String host) throws RemoteException
{
sem = new Semaphore(-3);
try {
...
server.asyncExecute( new MyCalculation(10000), this );
server.asyncExecute( new MyCalculation(1000), this );
server.asyncExecute( new MyCalculation(10), this );
server.asyncExecute( new MyCalculation(50), this );
sem.Down();
System.exit(0);
} catch (...) {...}
}
public void workCompleted( WorkRequest request, Object result )
throws RemoteException
{
//.. process result
sem.Up();
}
}
29. Example 5: Semaphore
import java.io.*;
public class Semaphore {
private int count = 0;
public Semaphore(int i) {
count = i;
}
public Semaphore() {
count = 0;
}
public synchronized void init(int i) {
count = i;
}
public synchronized void Down() {
boolean interrupted = false;
while (count == 0) {
try {wait();}
catch (InterruptedException ie) {interrupted=true;}
}
count--;
if (interrupted) Thread.currentThread().interrupt();
}
public synchronized void Up() {
count++;
notify();
}
}
30. RMI: Further Topics
RMI Object Persistence. RMI activation allows a remote
object to be stored away (in a database, for example) and
automatically reincarnated when it is needed.
RMI, CORBA, and IIOP. CORBA (Common Object
Request Broker Architecture) is a distributed object standard
that allows objects to be passed between programs written in
different languages. IIOP (Internet Inter-Object Protocol) is
being used by RMI to allow limited RMI-to-CORBA
interoperability.