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148 lines
3.8 KiB
Java
148 lines
3.8 KiB
Java
Access an ejb from a servlet
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package com.ack.web.servlet;
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import java.io.IOException;
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import java.io.PrintWriter;
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import javax.naming.Context;
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import javax.naming.InitialContext;
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import javax.naming.NamingException;
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import javax.rmi.PortableRemoteObject;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import com.ack.j2ee.ejb.session.Lawyer;
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import com.ack.j2ee.ejb.session.LawyerHome;
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/**
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* web.xml configuration part of the an ejb component
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*
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* <web-app>
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...
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<ejb-ref>
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<ejb-ref-name>yoda</ejb-ref-name>
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<ejb-ref-type>Session</ejb-ref-type>
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<home>com.ack.j2ee.ejb.session.LawyerHome</home>
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<remote>com.ack.j2ee.ejb.session.Lawyer</remote>
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</ejb-ref>
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...
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</web-app>
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*
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* the vendor-specific mapping of the res-ref-name into their
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* own application server space, eg weblogic does the following
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* in a weblogic.xml file
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*
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<weblogic-web-app>
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...
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<reference-descriptor>
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...
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<ejb-reference-description>
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<ejb-ref-name>yoda</ejb-ref-name>
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<jndi-name>ejb/lawyer</jndi-name>
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</ejb-reference-description>
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...
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</reference-descriptor>
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...
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</weblogic-web-app>
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*/
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public class AccessAnEjbFromAServlet extends HttpServlet {
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private Context ctx;
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public void init() throws ServletException {
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try {
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// lets share the context for ejb lookup for
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// this servlet's incoming requests
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ctx = new InitialContext();
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}
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catch( NamingException nex ) {
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throw new ServletException( "couldn't locate JNDI context", nex );
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}
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}
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public void doGet( HttpServletRequest req, HttpServletResponse res )
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throws ServletException, IOException {
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res.setContentType( "text/html" );
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PrintWriter pw = res.getWriter();
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try {
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// get reference to business interface from home interface
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Lawyer lawyer = getLawyer();
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// use the business interface
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lawyer.sendHimDown( "bad guy" );
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// let application server reclaim ejb resources
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lawyer.remove();
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}
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catch( LawyerException lex ) {
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pw.println( lex.getMessage() );
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}
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catch( Exception ex ) {
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log( "problem using the lawyer", ex );
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pw.println( ex.getMessage() );
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}
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pw.println( "well, that wasn't so bad" );
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}
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private Lawyer getLawyer() throws LawyerException {
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try {
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Object ejbObject = null;
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// get hold of the object you want by name
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synchronized( this ) {
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System.out.println( "calling on yoda..." );
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ejbObject = ctx.lookup( "java:comp/env/yoda" );
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}
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// narrow retrieved object into specific expected type
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LawyerHome home = (LawyerHome) PortableRemoteObject.
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narrow( ejbObject, LawyerHome.class );
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return home.create();
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}
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catch( Exception ex ) {
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log( "problem getting hold of a lawyer", ex );
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throw new LawyerException( ex.getMessage() );
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}
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}
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}
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class LawyerException extends Exception {
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public LawyerException( String str ) {
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super( str );
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}
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}
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/**
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*
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* This is the web.xml configuration
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*
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<web-app>
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...
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<ejb-ref>
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<description>bring forth the yoda lawyer</description>
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<ejb-ref-name>yoda</ejb-ref-name>
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<ejb-ref-type>Session</ejb-ref-type>
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<home>com.ack.j2ee.ejb.session.LawyerHome</home>
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<remote>com.ack.j2ee.ejb.session.Lawyer</remote>
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</ejb-ref>
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</web-app>
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*
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* But the vendor-specific xml file must map this
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* ejb-ref-name to the name in the JNDI space, for
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* example, in weblogic we have the weblogic.xml,
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*
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<weblogic-web-app>
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<reference-descriptor>
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<ejb-reference-description>
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<ejb-ref-name>yoda</ejb-ref-name>
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<jndi-name>ejb/lawyer</jndi-name>
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</ejb-reference-description>
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</reference-descriptor>
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</weblogic-web-app>
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*/
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