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Apachecon 2002 Struts

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    Apachecon 2002 Struts Apachecon 2002 Struts Presentation Transcript

        • Building Web Applications With The Struts Framework
        • Session WE06 – 11/20/2002 – 10:00-11:00
        • Craig R. McClanahan
        • Senior Staff Engineer
        • Sun Microsystems, Inc.
    • Session Outline
      • Web Applications Backgrounder
      • The Model-View-Controller Architecture
      • The Struts Framework
      • Building A Web Application With Struts
      • Resources
        • Web Applications Backgrounder
    • Web Applications Backgrounder
      • Web applications run over the HTTP protocol:
        • Request/response oriented
        • Stateless
      • Web applications use varied presentation (markup) languages, and talk to varied client hardware devices:
        • “ Standard HTML” -- not!
        • Varying dynamic and JavaScript capabilities
        • Wireless devices vary in capabilities, language dialect, and input device support
    • Simple Solutions ... for Simple Problems
      • For relatively simple applications, a simple architecture works fine
      • For each page in the user interface ...
        • Create a servlet, JSP page, or something similar
        • The page includes:
          • Logic to create the user interface
          • Logic to retrieve required information from the database
          • Logic to perform the appropriate business transaction
          • Logic to update the corresponding database information
        • And it's all mixed together in one source file
      • This works fine for a Guest Book app, but what about something bigger?
    • What About Large Scale Applications?
      • Disparate skill sets required:
        • Presentation Layer -- User interface design, visual appearance, interaction model
        • Application Layer – Functional business logic to perform required transactions
        • Persistence Layer – Databases, directory servers, messaging, Enterprise JavaBeans TM (EJBs)
        • Application Deployment – Networks, firewalls, public key infrastructures, load balancing, failover
      • We need a fundamental organizing principle:
        • The Model-View-Controller (MVC) architecture
        • The Model-View-Controller (MVC) Architecture
    • The Model-View-Controller Architecture
      • Divides the overall functionality of an application into three layers:
        • Model Layer – Contains the functional business logic of the application, as well as a representation of the persistently stored data backing the application
        • View Layer – Contains the user interface, including mechanisms to accept user input and render results
        • Controller Layer – Contains the logic that manages the flow of individual requests, dispatching to the appropriate business logic component
    • The Model Layer
      • Functional business logic:
        • Should be modelled as JavaBeans or Session EJBs
        • Should be reusable in non-web environments
        • API exposes public methods for each logical unit of work (while hiding the details)
      • Persistent data storage:
        • Should manage permanent storage of application data
        • Typically shared across many applications
        • API should expose data retrieval and storage operations (while hiding the mechanisms)
    • The View Layer
      • Creation of the user interface:
        • Typically in HTML or an XML-based dialect
        • Normally a combination of static and dynamic content
      • Actual content varies depending on:
        • Device or browser type
        • User preferences / personalization
        • Internationalization and localization requirements
        • Accessibility requirements
    • The Controller Layer
      • Incoming requests flow through a common path:
        • Received by common component
        • Standardized request pre-processing
        • Dispatch to request-specific model component (business logic)
        • Forward to business-logic-specified view component
        • Standardized request post-processing
      • Often called “Model 2 Design” in the JSP/Servlet community
      • In modern design pattern terminology, Struts implements the front controller pattern.
        • The Struts Framework – An Implementation of the MVC Architecture
    • The Struts Framework – Architecture
    • The Struts Framework – Model Layer
      • Struts does not restrict implementation techniques for model layer
        • JDBC-accessed databases
        • Enterprise JavaBeans
        • O-R mapping tools
      • Optional JDBC connection pool available
      • Common design pattern:
        • Action acquires information from persistence tier
        • Exposes information as request/session attributes
        • View layer pulls data from attributes for display
    • The Struts Framework – View Layer
      • Form Bean maintains state of form input fields across requests:
        • ActionForm – Standard JavaBean design pattern
        • DynaActionForm – Property names and types defined in Struts configuration file
      • In addition to properties, form beans define two standard methods:
        • reset() -- Reset form properties to initial state
        • validate() -- Perform field-level validations
      • Form bean properties are typically Strings
        • Allows redisplay of invalid input
    • The Struts Framework – View Layer
      • Internationalization Support enables locale-specific applications
        • Locale – Standard Java class representing a choice of language and/or country
        • MessageFormat – Standard Java class representing an individual message with replaceable parameters:
          • “ {0} is not a valid credit rating”
        • MessageResources – Struts abstraction around sets of messages for supported locales
        • ActionErrors / ActionMessages – Struts collections of localized messages
    • The Struts Framework – View Layer
      • JSP Custom Tag Libraries – If you are using JSP pages for your presentation
        • struts-bean.tld – Fundamental bean manipulation and internationalization
        • struts-html.tld – “Smart” HTML elements
        • struts-logic.tld – Basic conditionals and iteration
        • struts-template.tld – Basic layout management
    • The Struts Framework – View Layer
      • Standard tag libraries added in Struts 1.1:
        • struts-nested.tld -- “Nested” variants of standard tags that resolve relative references against beans
        • struts-tiles.tld – Full features layout management library
      • Contributed libraries added in Struts 1.1:
        • struts-xxx-el.tld – Versions of standard Struts tag libraries that support the expression language syntax of JSP Standard Tag Library
    • The Struts Framework – View Layer
      • Validation Framework
        • No-code-required field level validations
        • Configured in an XML document included in the web application
        • Optionally generates client side JavaScript to enforce validation rules
        • Extensible architecture
    • The Struts Framework – Controller Layer
      • ActionServlet – Standard implementation of controller
      • At application startup, reads configuration file and initializes resources
        • [Struts 1.1] PlugIn – General start/stop hook
      • On each request, implements the standard Struts request processing lifecycle (in Struts 1.1, implemented in RequestProcessor )
      • Specialization / customization via subclassing
      • [Struts 1.1] Sub-application modules support
    • The Struts Framework – Controller Layer
      • Action – Standard base class for business logic components and adapters:
        • Mapped to logical names by request processor
        • Single instance per application (must be thread safe)
        • Instantiated as needed, like servlets
      • Implements the “Command Pattern”
        • execute() -- Invoked for each request
        • Can (but typically does not) create response content directly
        • Typically returns ActionForward to select resource to prepare response
    • The Struts Framework – Controller Layer
      • Standard Request Processing Lifecycle 1:
        • processLocale() -- Record user's locale preference (if not already present)
        • processPreprocess() -- general purpose pre-processing hook
        • processMapping() -- select Action to be utilized
        • processRoles() -- perform security role-based restrictions on action execution
        • processActionForm() -- Create or acquire an appropriate ActionForm instance
    • The Struts Framework – Controller Layer
      • Standard Request Processing Lifecycle 2:
        • processPopulate() -- Copy the request parameters into the form bean properties
        • processValidate() -- Call form bean's validate() method
        • processActionCreate() -- Create or acquire an appropriate Action instance
        • processActionPerform() -- Call action's execute() method
        • processActionForward() -- Process returned ActionForward instance (if any)
    • The Struts Framework – Controller Layer
      • XML Configuration Document (/WEB-INF/struts-config.xml)
        • Standard place to configure all aspects of the application's behavior
        • DTD included for optional (but recommended) validation
        • Logical-to-physical mappings for Actions, ActionForms, and ActionForwards
        • General configuration settings
      • [Struts 1.1] Configuration Document per module if more than one
    • The Struts Framework – Commons Libraries
      • Non-Struts Specific Logic Factored Out:
        • commons-beanutils – Generic bean property manipulation
        • commons-collections – Extensions to standard Java2 collections classes
        • commons-dbcp – Optional JDBC connection pool
        • commons-digester – XML parsing for configuration files
        • commons-fileupload – Support library for HTML file uploads
    • The Struts Framework – Commons Libraries
      • Non-Struts Specific Logic Factored Out:
        • commons-logging – Application logging wrapper
        • commons-pool – Object pooling library
        • commons-resources – Message resources support library
        • Commons-validator – Field validation framework
        • Building Web Applications With Struts
    • Building Web Applications With Struts
      • Now that we understand the architecture of Struts, let's look at parts of an example app that is built with it
      • Struts includes a canonical example that is useful in determining whether you have installed things correctly
        • struts-example.war
      • Application models (part of) an email portal site that lets you maintain multiple subscriptions
    • Sample Application – Model Layer (Persistence Tier)
      • Modelled via a Data Access Object (DAO)
        • org.apache.struts.webapp.example.UserDatabase
      • public interface UserDatabase {
      • public User createUser(String username);
      • public void close() throws Exception;
      • public User findUser(String username);
      • public User[] findUsers();
      • public void open() throws Exception;
      • public void removeUser(User user);
      • public void save() throws Exception;
      • }
    • Sample Application – Model Layer (Persistence Tier)
      • Default implementation based on loading an XML document into memory:
        • o.a.s.e.memory.MemoryUserDatabase
      • JDBC-based (or LDAP-based) implementation is easy to imagine, and would be transparent to the business logic
      • Implementation selection implemented via a PlugIn ... see configuration file example later
    • Sample Application – Model Layer (Business Logic)
      • Two common Struts design patterns illustrated
      • View --> View --> Action
        • Welcome Page has link to logon page:
          • <html:link page=”/logon.jsp”>...</html:link>
        • Logon page instantiates LogonForm bean
        • Form submit goes to “/logon” action
      • View --> Action --> View --> Action
        • Setup action “/editRegistration?action=Edit” pulls data from “database” and populates form bean
        • Registration page “ /registration.jsp” displays current data
        • Form submit goes to “/saveRegistration” action
    • Sample Application – View Layer (logon.jsp)
      • <%@ page contentType=”text/html;charset=”UTF-8” %>
      • <%@ taglib uri=”/WEB-INF/struts-bean.tld”
      • prefix=” bean ” %>
      • <%@ taglib uri=”/WEB-INF/struts-html.tld”
      • prefix=” html ” %>
      • < html:html locale=”true”>
      • <head>
      • <title>
      • < bean:message key=”logon.title”/>
      • </title>
      • < html:base />
      • </head>
    • Sample Application – View Layer (logon.jsp)
      • <body bgcolor=”white”>
      • < html:errors />
      • < html:form action=”/logon” focus=”username”
      • onsubmit=”return validateLogonForm(this);”>
      • <table border=”0” width=”100%”>
      • <tr>
      • <th align=”right”> < bean:message key=”prompt.username”/>
      • </th>
      • <td align=”left”>
      • < html:text property=”username” size=”16”/>
      • </td>
      • </tr>
    • Sample Application – View Layer (logon.jsp)
      • <tr>
      • <th align=”right”> < bean:message key=”prompt.password”/>
      • </th>
      • <td align=”left”>
      • < html:password property=”password”
      • size=”16”/>
      • </td>
      • </tr>
      • </table></ html:form >
      • < html:javascript formName=”logonForm”
      • dynamicJavascript=”true”
      • staticJavascript=”false”/>
      • <script language=”Javascript” .../>
      • </body></ html:html >
    • Sample Application – Controller Layer
      • No application logic required – Struts does everything for you :-)
      • Controller functionality is configured via XML-based files:
        • struts-config.xml – Struts controller configuration
        • validation.xml – Validator framework configuration
        • web.xml – Web application configuration
    • Sample Application – Struts Configuration (struts-config.xml)
      • <struts-config>
      • <form-beans>
      • ...
      • <form-bean name=”logonForm”
      • type=” org.apache.struts.action.DynaActionForm ”>
      • <form-property name=”username”
      • type=” java.lang.String ”/>
      • <form-property name=”password”
      • type=” java.lang.String ”/>
      • </form-bean>
      • <form-bean name=”registrationForm”
      • type=” org.apache.webapp.example.RegistrationForm ”/>
      • ...
      • </form-beans>
    • Sample Application – Struts Configuration (struts-config.xml)
      • <global-forwards>
      • <forward name=”logoff” path=”/logoff.do”/>
      • <forward name=”logon” path=”/logon.do”/>
      • <forward name=”registration”
      • path=”/registration.jsp”/>
      • <forward name=”success”
      • path=”/mainMenu.jsp”/>
      • </global-forwards>
    • Sample Application – Struts Configuration (struts-config.xml)
      • <action-mappings>
      • <action path=” /editRegistration ”
      • type=” org.apache.struts.webapp.example.EditRegistrationAction ”
      • name=”registrationForm”
      • scope=”request” validate=”false”>
      • <forward name=”success”
      • path=”/registration.jsp”/>
      • </action>
      • <action path=” /saveRegistration ”
      • type=” org.apache.struts.webapp.example.SaveRegistrationAction ”
      • name=”registrationForm”
      • scope=”request” validate=”true”
      • input=”registration”/>
    • Sample Application – Struts Configuration (struts-config.xml)
      • <action path=” /logon ”
      • type=” org.apache.struts.webapp.example.LogonAction ”
      • input=”request”
      • name=”logonForm”
      • scope=”request”/>
      • ...
      • </action-mappings>
      • <controller>
      • <set-property property=”inputForward”
      • value=”true”/>
      • </controller>
      • <message-resources
      • parameter=” org.apache.struts.example.ApplicationResources ”/>
    • Sample Application – Struts Configuration (struts-config.xml)
      • <plug-in className=” org.apache.struts.webapp.example.memory.MemoryDatabasePlugIn ”>
      • <set-property property=”pathname”
      • value=”/WEB-INF/database.xml”/>
      • </plug-in>
      • <plug-in className=” org.apache.struts.validator.ValidatorPlugIn ”>
      • <set-property property=”pathnames”
      • value=”/WEB-INF/validator-rules.xml,
      • /WEB-INF/validation.xml”/>
      • </plug-in>
      • </struts-config>
    • Sample Application – Struts Configuration (validation.xml)
      • <form-validation>
      • <formset>
      • <form name=” logonForm ”>
      • <field property=”username”
      • depends=”minlength,...”>
      • <arg0 key=”prompt.username”/>
      • <arg1 key=”${var:minlength}”
      • name=”minlength”
      • resource=”false”/>
      • <var><var-name>minlength</var-name>
      • <var-value>3</var-value></var>
      • ...
      • </field>
      • ...
      • </form>
      • ...
      • </formset>
      • </form-validation>
    • Sample Application – Webapp Configuration (web.xml)
      • <web-app>
      • <servlet>
      • <servlet-name>Controller</servlet-name>
      • <servlet-class>
      • org.apache.struts.action.ActionServlet
      • </servlet-class>
      • <init-param>
      • <param-name>config</param-name>
      • <param-value>
      • /WEB-INF/struts-config.xml
      • </param-value>
      • </init-param>
      • <load-on-startup> 1 </load-on-startup>
      • </servlet>
    • Sample Application – Webapp Configuration (web.xml)
      • <servlet-mapping>
      • <servlet-name>Controller</servlet-name>
      • <url-pattern> *.do </url-pattern>
      • </servlet-mapping>
      • ...
      • </web-app>
        • Current Events
    • Struts 1.1 Release
      • When? “Real Soon Now”
      • What new features?
        • Apache Commons Libraries
        • DynaActionForm
        • Declarative Exception Handling
        • Nested Tag Library
        • PlugIn API
        • Sub-Application Module Support
        • (Contributed) STRUTS-EL Tag Libraries
    • Struts and JSTL
      • JSP Standard Tag Library (JSTL) 1.0:
        • Expression language (“${customer.address[“mailing”].city”)
        • General purpose actions (out, set, remove, catch)
        • Conditional actions (if, choose, when, otherwise)
        • Iterator actions (forEach, forTokens)
        • URL actions (import, url, redirect, param)
        • Internationalization actions (message, setLocale, bundle, setBundle, message, param, requestEncoding)
        • Formatting actions (timeZone, setTimeZone, formatNumber, parseNumber, formatDate, parseDate)
    • Struts and JSTL
      • JSP Standard Tag Library (JSTL) 1.0, continued:
        • SQL actions (not relevant in an MVC framework environment)
        • XML core actions (parse, out, set)
        • XML flow control actions (if, choose, when, otherwise, forEach)
        • XML transform actions (transform, param)
      • The struts-xxx-el libraries are a bridge for Struts developers who want to leverage JSTL tags, and expression language syntax, now
    • Struts and JSF
      • JavaServer Faces (currently under development in JSR-127)
      • Goals:
        • Standard GUI component framework for web applications
        • RenderKits for different rendering environments (browser vs. wireless device, different locales, etc.)
      • Struts will provide an integration library:
        • Requires changes to view layer and struts-config.xml file only !
        • Plugs in to RequestProcessor APIs
        • Resources
    • This Presentation Online
      • StarOffice 6.0:
        • http://www.apache.org/~craigmcc/apachecon-2002-struts.sxi
      • Powerpoint:
        • http://www.apache.org/~craigmcc/apachecon-2002-struts.ppt
    • Internet Technologies
      • Hypertext Markup Language (HTML) 4.01:
        • http://www.w3.org/TR/html4/
      • Hypertext Transfer Protocol (HTTP) 1.1:
        • http://www.ietf.org/rfc/rfc2616.txt
      • Uniform Resource Identifiers (URI):
        • http://www.ietf.org/rfc/rfc2396.txt
    • Model Layer – Standard Java APIs
      • JavaBeans:
        • http://java.sun.com/products/javabeans/
      • Java Database Connectivity (JDBC):
        • http://java.sun.com/products/jdbc/
      • Java Data Objects:
        • http://java.sun.com/products/jdo/
        • http://jcp.org/jsr/detail/12.jsp
      • Java Naming and Directory Interface:
        • http://java.sun.com/products/jndi/
      • Enterprise JavaBeans (EJB):
        • http://java.sun.com/products/ejb/
    • Model Layer – Persistence Frameworks
      • Castor:
        • http://castor.exolab.org/
      • Java Data Objects:
        • http://java.sun.com/products/jdo/
      • Object/Relational Bridge:
        • http://jakarta.apache.org/ojb/
      • Torque:
        • http://jakarta.apache.org/turbine/torque/
    • View Layer – Standard Java APIs
      • Servlets:
        • http://java.sun.com/products/servlet/
      • JavaServer Pages (JSP):
        • http://java.sun.com/products/jsp/
      • JSP Standard Tag Library (JSTL):
        • http://java.sun.com/products/jsp/jstl/
      • JavaServer Faces:
        • http://java.sun.com/j2ee/javaserverfaces/
        • http://jcp.org/jsr/detail/127.jsp
    • Struts Resources
      • The Struts and Commons Web Sites:
        • http://jakarta.apache.org/struts/
        • http://jakarta.apache.org/commons/
      • Recent Books About Struts:
        • Cavaness, Chuck; Programming Jakarta Struts ; O'Reilly
        • Goodwill, James; Mastering Jakarta Struts ; John Wiley
        • Husted, Ted; Java Web Development With Struts ; Manning
        • Spielman, Sue; The Struts Framework: Practical Guide for Programmers ; Morgan Kaufman
        • Turner, James; Struts Kick Start ; Sams
    • Design Patterns Resources
      • The Java Blueprints Web Site:
        • http://java.sun.com/blueprints/
      • Design Patterns Books:
        • Gamma, Erich (et. al.); Design Patterns: Elements of Reusable Object-Oriented Software ; Addison-Wesley
        • Alur, Deepak (et. al.); Core J2EE Patterns: Best Practices and Design Strategies ; Prentice Hall
        • Q & A