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.
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.
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.
This slide give the basic introduction about UML diagram and it's types, and brief intro about Activity Diagram, use of activity diagram in object oriented programming language..
This is all about socket programming in java using TCP and UDP socket and an example of simple Echo Server.
Also includes concepts of the socket, Socket class and methods and use of those.
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
Client Server Architecture in Software engineeringpruthvi2898
What is client?
A client is a single-user workstation ...
What is server?
A server is one or more multi-user processors ..
What is client server architecture?
Client-server architecture is a network architecture ...
Types of client server architecture.
2 types
1) 2-tier
2) 3-tier
Overview of EJB technology.
Enterprise Java Beans (EJB) is a server-side component technology for Java EE based systems (JEE).
Beans are business logic components that implement a standard interface through which the bean is hooked into the bean container (= runtime object for bean).
A Java class implementing one of the standard bean interfaces is an Enterprise Java Bean. Beans can be accessed remotely, usually from a client tier.
The EJB standard was developed to provide a common framework for solving recurring problems in business application development like persistence, transactions,
security and runtime and lifecycle management. The EJB standard evolved greatly over time. EJB version 1 and 2 were complex and required to implement many interfaces
and exception handling in EJBs. EJB version 3 brought great simplifications and did away with interfaces by replacing these with annotations which provide greater flexibility while keeping complexity low. EJBs come in 3 different flavors: Stateless and stateful session beans and message driven beans. Entity beans of EJB version 1 and 2 were replaced by the Java Persistence API in EJB version 3.
SOAP is a simple and flexible messaging framework for transferring information specified in the form of an XML infoset between an initial SOAP sender and ultimate SOAP receiver.
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.
This slide give the basic introduction about UML diagram and it's types, and brief intro about Activity Diagram, use of activity diagram in object oriented programming language..
This is all about socket programming in java using TCP and UDP socket and an example of simple Echo Server.
Also includes concepts of the socket, Socket class and methods and use of those.
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
Client Server Architecture in Software engineeringpruthvi2898
What is client?
A client is a single-user workstation ...
What is server?
A server is one or more multi-user processors ..
What is client server architecture?
Client-server architecture is a network architecture ...
Types of client server architecture.
2 types
1) 2-tier
2) 3-tier
Overview of EJB technology.
Enterprise Java Beans (EJB) is a server-side component technology for Java EE based systems (JEE).
Beans are business logic components that implement a standard interface through which the bean is hooked into the bean container (= runtime object for bean).
A Java class implementing one of the standard bean interfaces is an Enterprise Java Bean. Beans can be accessed remotely, usually from a client tier.
The EJB standard was developed to provide a common framework for solving recurring problems in business application development like persistence, transactions,
security and runtime and lifecycle management. The EJB standard evolved greatly over time. EJB version 1 and 2 were complex and required to implement many interfaces
and exception handling in EJBs. EJB version 3 brought great simplifications and did away with interfaces by replacing these with annotations which provide greater flexibility while keeping complexity low. EJBs come in 3 different flavors: Stateless and stateful session beans and message driven beans. Entity beans of EJB version 1 and 2 were replaced by the Java Persistence API in EJB version 3.
SOAP is a simple and flexible messaging framework for transferring information specified in the form of an XML infoset between an initial SOAP sender and ultimate SOAP receiver.
Resilient and Adaptable Systems with Cloud Native APIsVMware Tanzu
SpringOne 2021
Session Title: Resilient and Adaptable Systems with Cloud Native APIs
Speakers: Olga Maciaszek-Sharma, Senior Member of Technical Staff at VMware; Spencer Gibb, Spring Cloud Core Lead at VMware
The RMI Java Remote Method Invocation Application Programming Interface (API), or Java RMI, is a Java API that performs the object-oriented equivalent of remote procedure calls (RPC), with support for direct transfer of serialized Java objects and distributed garbage collection.
The original implementation depends on Java Virtual Machine (JVM) class representation mechanisms and it thus only supports making calls from one JVM to another. The protocol underlying this Java-only implementation is known as Java Remote Method Protocol (JRMP).
• In order to support code running in a non-JVM context, a CORBA version was later developed.
• In order to support code running in a non-JVM context, a CORBA version was later developed.
A Pulsar Use Case In Federated Learning - Pulsar Summit NA 2021StreamNative
Federated learning (FL) is a machine learning technique that enables multiple decentralized organizations to train a model without exposing local data samples. Instead, during the training, lots of encrypted messages will be exchanged among the participants to aggregate the global model. Due to the message is so important and its requirements of real-time and sequential, it brings some challenges to the transmission.
In this session, we will talk about how to address the above challenge with the Apache Pulsar project, and we will go through the details about how popular FL project FATE(https://github.com/FederatedAI/FATE) use Pulsar to do federated training.
Scaling Databricks to Run Data and ML Workloads on Millions of VMsMatei Zaharia
Keynote at Scale By The Bay 2020.
Cloud service developers need to handle massive scale workloads from thousands of customers with no downtime or regressions. In this talk, I’ll present our experience building a very large-scale cloud service at Databricks, which provides a data and ML platform service used by many of the largest enterprises in the world. Databricks manages millions of cloud VMs that process exabytes of data per day for interactive, streaming and batch production applications. This means that our control plane has to handle a wide range of workload patterns and cloud issues such as outages. We will describe how we built our control plane for Databricks using Scala services and open source infrastructure such as Kubernetes, Envoy, and Prometheus, and various design patterns and engineering processes that we learned along the way. In addition, I’ll describe how we have adapted data analytics systems themselves to improve reliability and manageability in the cloud, such as creating an ACID storage system that is as reliable as the underlying cloud object store (Delta Lake) and adding autoscaling and auto-shutdown features for Apache Spark.
This is an introduction into distributed computing using Java Remote Method Invocation (RMI) technology. RMI allows java applications to communicate to server or distributed applications across the network seamlessly. RMI can leverage proprietary protocols or standard CORBA IIOP protocol to send/receive messages. The presentation covered the following topics.
Presentation
------------
Session Outline:
- Overview of RMI
- Features of RMI
- Layers in RMI
- Creating an application
- Conclusion
Example code available at ChrisMatthews.us
Author: Chris Matthews
Copyright: eLink Business Innovations 2002
Vladimir Bacvanski and Rafael Coss
Common demands for Web 2.0 application are rich interactivity and ability to handle large volumes of data. Join us to see
how to integrate IBM DB2, IBM WebSphere sMash and high-performance data access through IBM Optim pureQuery. This
combination provides a way to rapidly develop data-centric, scalable dynamic Web applications. See how we begin with a DB2
database, access the data with Optim pureQuery, use business objects in Groovy, and expose them to users through Dojo AJAX framework.
RMI is an API which allows an object to invoke a method on an object that exists in another address space, which could be on the same machine or on a remote machine. Through RMI, object running in a JVM present on a computer (Client side) can invoke methods on an object present in another JVM (Server side).
RAISE Lab at Dalhousie University
aims to develop tools and technologies for intelligent automation in software engineering. An overview is presented by Dr. Masud Rahman, Assistant Professor, Faculty of Computer Science, Dalhousie University, Canada.
The Forgotten Role of Search Queries in IR-based Bug Localization: An Empiric...Masud Rahman
Being light-weight and cost-effective, IR-based approaches for bug localization have shown promise in finding software bugs. However, the accuracy of these approaches heavily depends on their used bug reports. A significant number of bug reports contain only plain natural language texts. According to existing studies, IR-based approaches cannot perform well when they use these bug reports as search queries. On the other hand, there is a piece of recent evidence that suggests that even these natural language-only reports contain enough good keywords that could help localize the bugs successfully. On one hand, these findings suggest that natural language-only bug reports might be a sufficient source for good query keywords. On the other hand, they cast serious doubt on the query selection practices in the IR-based bug localization. In this article, we attempted to clear the sky on this aspect by conducting an in-depth empirical study that critically examines the state-of-the-art query selection practices in IR-based bug localization. In particular, we use a dataset of 2,320 bug reports, employ ten existing approaches from the literature, exploit the Genetic Algorithm-based approach to construct optimal, near-optimal search queries from these bug reports, and then answer three research questions. We confirmed that the state-of-the-art query construction approaches are indeed not sufficient for constructing appropriate queries (for bug localization) from certain natural language-only bug reports. However, these bug reports indeed contain high-quality search keywords in their texts even though they might not contain explicit hints for localizing bugs (e.g., stack traces). We also demonstrate that optimal queries and non-optimal queries chosen from bug report texts are significantly different in terms of several keyword characteristics (e.g., frequency, entropy, position, part of speech). Such an analysis has led us to four actionable insights on how to choose appropriate keywords from a bug report. Furthermore, we demonstrate 27%–34% improvement in the performance of non-optimal queries through the application of our actionable insights to them. Finally, we summarize our study findings with future research directions (e.g., machine intelligence in keyword selection).
Preprint: https://bit.ly/39nAoun
Publication URL: https://bit.ly/3xVUxlq
Replication package: https://bit.ly/36T8oxL
More details: https://web.cs.dal.ca/~masud
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
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Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
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Introduction to AI for Nonprofits with Tapp Network
Java RMI Presentation
1. JAVA REMOTE METHOD INVOCATION
(RMI)
Mohammad Masudur Rahman
mor543@mail.usask.ca
Department of Computer Science
University of Saskatchewan
Saskatoon, SK, S7N5C9
Date: April 09, 2013
13. A SIMPLE RMI APPLICATION
1
SERVER
oWriting an Interface
o Implementing an
Interface
o Binding Interface
CLIENT
o Writing a Client
DEPLOYMENT
o Manage Security
Settings
o Running Server &
Client
2
3
13
14. SERVICE INTERFACE: AN AGREEMENT
BETWEEN SERVER & CLIENT
Factorial Operation
Check Prime Operation
Square Operation
14
18. A SIMPLE RMI APPLICATION
1
SERVER
oWriting an Interface
o Implementing an
Interface
o Binding Interface
CLIENT
o Writing a Client
DEPLOYMENT
o Manage Security
Settings
o Running Server &
Client
2
3
18
21. A SIMPLE RMI APPLICATION
1
SERVER
oWriting an Interface
o Implementing an
Interface
o Binding Interface
CLIENT
o Writing a Client
DEPLOYMENT
o Manage Security
Settings
o Running Server &
Client
2
3
21
22. SERVER DEPLOYMENT: START RMI
REGISTRY
To start RMI registry on windows
To start RMI registry on Unix
22
23. SERVER DEPLOYMENT: COMPILE THE
SERVER
Compile both MathService interface and
MathServiceProvider class
23
25. SECURITY DEPLOYMENT: CREATE SECURITY
POLICY FILE (BOTH CLIENT & SERVER)
Create a security policy file called no.policy with
the following content and add it to CLASSPATH
This step implies for both server and client
25
31. STRENGTH OF JAVA RMI
Object Oriented: Can pass complex object rather
than only primitive types
Mobile Behavior: Change of roles between client
and server easily
Design Patterns: Encourages OO design patterns
as objects are transferred
Safe & Secure: The security settings of Java
framework used
Easy to Write /Easy to Use: Requires very little
coding to access service
31
32. STRENGTH OF JAVA RMI
Connects to Legacy Systems: JNI & JDBC
facilitate access.
Write Once, Run Anywhere: 100% portable, run on
any machine having JVM
Distributed Garbage Collection: Same principle like
memory garbage collection
Parallel Computing: Through multi-threading RMI
server can serve numerous clients
Distributed Computing Solutions: Available from
JDK 1.1, can communicate between all versions of
JDKs
32
33. WEAKNESS OF JAVA RMI
Tied to Java System: Purely Java-centric
technology, does not have good support for legacy
system written in C, C++, Ada etc.
Performance Issue : Only good for large-grain
computation
Security Restrictions & Complexities: Threats
during downloading objects from server, malicious
client request, added security complexity in policy
file.
Overhead: Extra usage of rmic tool.
33
35. CASE STUDY: JAVA RMI
Language Dependence:
RMI service interface is in
Java
CORBA service interface is
platform independent
VS.
CORBA
Mobile Behavior
Server and client can change
roles in RMI
Not feasible in CORBA
Performance Issue:
RMI needs extra overhead for
conversion from byte code to machine
code
CORBA performs better for massive
computation like fluid mechanics
35
36. CASE STUDY: JAVA RMI
Ease of Use:
RMI is easy to master for
experienced programmers.
CORBA is a rich, extensive
family of standards, hard to
master
VS.
CORBA
Maturity of Technology
RMI is less matured
CORBA is more matured
and already has many
implementations running
36
37. JAVA RMI CUSTOMERS
IBM
Swiss Federal Supreme Court
CEAS Consulting
Avitek
Different Chat service Company
More can be found here:
http://www.cs.mun.ca/~paul8/jdk1.2beta3/docs/guid
e/rmi/examples.html
37
38. CORBA CUSTOMERS
USA AG
Cisco Systems
American Airlines
BHP Information Technology
More can be found here:
http://www.corba.org/success.htm
38
39. CASE STUDY: JAVA RMI
VS.
CORBA
Results of case study:
o
o
No one is better than other necessarily
Applicability of one on another depends on
Purpose of the application
Experience of the designer and developer
Necessity of interoperability with non-java systems.
39
40. CONCLUSION
Distributed Object Technology
Object level abstraction
Object version of Java RPC
Java centric Technology
Comparable to CORBA, SOAP
Provides non-java support with the help IDL, IIOP
and CORBA
Lightweight and Easy to use
Object serialization
Concurrent support for clients
40
42. REFERENCES
[1].Advantages of java RMI
http://www.oracle.com/technetwork/java/javase/tech/index-jsp-138781.html
[2] Java RMI architecture. http://www.cs.mun.ca/michael/java/jdk1.1-beta2docs/guide/rmi/rmi-arch.doc.html
[3] Introduction to java RMI
http://www.javacoffeebreak.com/articles/javarmi/javarmi.html.
[4] Java RMI: Remote method invocation.
http://www1.cs.columbia.edu/dcc/nestor/presentations/java-rmi/java-rmihandouts.pdf
[5] Disadvantages of RMI. http://www.coderanch.com/t/180297/javadeveloperSCJD/certification/RMI-Advantages-Disadvantages.
[6] Background of java rmi.
http://docs.oracle.com/javase/1.5.0/docs/guide/rmi/spec/rmi-intro2.html.
[7] How RMI works.
http://www.sce.carleton.ca/netmanage/simulator/rmi/RMIExplanation.htm
Please contact mor543@mail.usask.ca to get more.
42
Editor's Notes
Hello everybody, welcome to my presentation.This is Mohammad Masudur Rahman.Today, I am going to talk about a very interesting topic about distributed computing called Remote Method Invocation.Hope you will enjoy the topic.
RMI is copyrighted by Sun Micro systemCurrently SUN is taken by Oracle, so, now this technology belongs to Oracle corporation.
In my presentation, I am going to cover the following topics I am not going to read it out, but we will try to go step by step.
Before discussing about Java RMI,the very first thing I would like to focus.What is a distributed object technology (DOT)?Also, what is the difference between web application and web service?So, concept is pretty simple like this diagram. When a machine can access the functionality of an object situated in a remote machine and exploit the computation power of the remote machine, then we can call it as a distributed object technology (DOT)Java RMI is a perfect example of distributed object technology. Other similar types of technology is CORBA, SOAP etc.
As mentioned, Java RMI is a distributed object based technology that means it provides object level abstraction to the developer.For example, the developer needs to access some functionality of a remote object, Java RMI manages to allow the developers to call that remote object from his program just like a local class object. This was a cool thing when the concept was first started by Sun Microsystems and whole features were packaged as a Java Library with SDK.It is also considered as an object version of Java RPC which provides procedure level abstraction to the developer.Java RMI is basically a Java based technology and any machine containing JVM can host a distributed object server or client. However, it involves several components like service interface, RMI registry, skeleton, stubs etc which will discuss in the later slides.The are also some advanced features related to RMI like object serialization, parameter marshalling on which we will try to provide some overview.
Lets take a look into the technology hierarchy.The primary communication technology is Socket in Java : abstraction is low level, that means developer needs to think about more details about the technology rather than his application which is time-consuming.The next level is RPC, which provides method level abstraction, that means to call a remote method, you have to provide the method name and parameters though some RPC Client to get access to the functionality; that means, still you need to care about method name, type and # of parameters which may not be comfortable for all.The next level is object level technology which provides object level abstraction. Other parallel object technology is CORBA by OMG and SOAP by Microsoft.CORBA is C++ in server, but the service interface is implemented in IDL (Interface definition language) which is platform independent, so, any client can communicate with it. IDL creates different service interfaces for different clients.SOAP is mainly intended for web service architecture. Any client having access to WSDL file can actually access the service.
XDR = External data representation, a data format for network transmission, developed by Sun Microsystems, 1980 Encoding > XDR >Decoding of data.Base unit is 4 bytes.CORBA= Common Object Request Broker Architecture, client and server both communicate with the ORB (Object Request Broker) to get and provide service.IIOP = ORB protocol over the Internet which started on 1994 to provide a greater degree of interoperability.Java IDL = Provides Java interface definition to different other languages.RMI IIOP=Java RMI over IIOP, that means RMI uses IIOP to exploit the CORBA features like OMG IDL or non-java platform access.
Lets focus on RMI architecture. The discussion will be two-folds:Layered based architectureWorking principles based
Here, we can see a list of layers in the RMI protocol.In the application layer, there are client and server who are the end-consumer and end-producer of the service. They communicate with intermediate layer called stub-skeleton layer.In stub-skeleton layer, stub is related to client application which actually transmits the request to the next level. The skeleton is a component which is associated with server and is responsible to make the actual request to the server.Remote reference layer contains the RMI registry and it works like a ORB in CORBA, that means, it handles the request and response between client and server. Once the client gets the remote object reference from the RMI registry, it can make request and this layer transmits that request to the appropriate server. Again, when server responds, it also sends back the response to the client. It also manages other advanced tasks like object activation , object serialization management, distributed garbage collection etc.Transport layer handles network communication between client and server.
We have discussed these already.
Now comes the working principles.We can see the following steps:Client requests for the remote object reference to naming serviceOnce the naming service locates the server host, RMI registry provides a stub (proxy) of remote object.Client can make call using the stubBasically, the request from the stub is sent to the server skeleton which makes the actual request to the remote object.Similarly, the server response is sent back through skeleton and stub to the client.
Now, we will show how to develop a simple RMI application.
There are 3 major steps for this development.Service contract establishment and server application developmentClient application developmentDeployment of service
First comes the service contract.Suppose, the client and server are agreed upon this contract that there will be 3 operations:Factorial operationPrime check operationSquare operationI kept the examples simple for easy understanding.
And here is the complete interface. We developed it using Java interface. We named it MathService.
Here, the serverapplication implements the service interface.
This code binds the MathService to the RMI registry so that client app can get the reference of the serviceAnd consume the service.Interestingly, client can actually access the reference of interface MathService to make call, however, the respond is provided by the object implementing the service.
Now comes the client application development.
Here, we can see, client accesses the Naming. lookup() method to get the reference of the remote object.
Once it gets the reference, client can call the method just like it is calling a local object method.This is the strength of Java RMI technology.
Now comes the deployment.
We need to start the RMI registry service to deploy the remote object; server object.
Here we are compiling both service and server object.
Then we are creating skeleton of server object. This step is deprecated from JDK 1.5 as JDK automatically creates it.The developer does not need to do it manually now.
Now comes the crucial part on which often most of time we get stuck.That is the security policy of Java RMI.The default security does not support the RMI call, so, we need to set custom permission for the call to the security manager.This phase is required for both the client and server.Basically, we have to create a <any name>.policy file with this content. Here, we allowed all types of call associated with Java RMI;That is why it contains AllPermission.
This is how the server object should be deployed.
This is how we did.
This is how the client needs to be run for RMI service access. Please note that we have to specify the host name.
This is how we did for the client. However, we also developed the Java object serialization by this time.
There are advance stuffs which I would like to provide some overview.Java Object serialization: It involves converting the object into a sequence of byte streams where there needs a swapping of java object between client and the server. Basically, if client or server uses a user-defined class as parameters, then they need the object serialization.Parameter Marshalling is a type of serialization for parameters handled by the stub-skeleton layer. Demarshalling refers to de-serialization.Object Activation: In some scenarios, server may not be running always, then object reference layer activates the target remote object (server) to enable it to respond to the client’s request. Common for infrequent RMI call.The detail discussion of those topics is beyond this tutorial, because each of them will be a single tutorial.
These are strengths of Java RMI.-Object oriented, object level abstraction.-Mobile behavior: that means the roles between client and server can be exchanged easily.-It supports the design pattern-sate and secure like the Java technology.
-It can support the legacy system.-Write once, run everywhere-Distributed garbage collection, like the one provide by Java.-facilitates the parallel computing.-Widely supported by different versions of JDK, as it was from the beginning, JDK 1.1
It also got some weaknesses.-Tied to Java system, that means it a Java only technology, cant communicate well with the non-java platform.-Due to byte code step, the computation is slower.-Additional complexity for security which many developers didn’t like.-Extra step with rmic compilation
Now, we will do a comparative study between RMI and its parallel technologyCORBA
We will choose several perspective to compare between these two technologies:Language dependence: Java is tied to Java, that means client server and interface all are in java, but its not the case in CORBA. The core/server of CORBA in C++, but the IDL provides language specific service interface, so that any client can call the server. This makes CORBA platform language independent service.Mobile behavior: Java RMI can show it as the roles between client and server can be easily exchanged; not possible for CORBAPerformance Issue: For byte code step, Java RMI fall backs in heavy computation. On the other hand, C++ of CORBA is compiling language and performs faster
There are more:4. Ease of use: RMI is easy to use, but CORBA is complex and may not easy for all.5. Maturity: CORBA is a matured technology and already lots of applications are using this technology, whereas RMI is less matured compared to it.
Java RMI has got several big customers due to its remarking features.
CORBA is a well established technology and started earlier than RMI. It got huge audience. Please check the link for details.Few are shown here.
So>None is better than otherYou need to choose based on the scope and type of the technical requirements.For example, if you need low overhead, easy to use technique and platform independence is not a requirement, then you can choose RMIFor opposite reasons, you can choose CORBA, but beware of the expertise of the developers
So, we have got couple of conclusions to make.Discuss on your own.