92 lines
2.5 KiB
Java
92 lines
2.5 KiB
Java
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Accessing a data source 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 java.sql.Connection;
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import java.sql.Date;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import java.sql.Statement;
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import javax.naming.Context;
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import javax.naming.InitialContext;
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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 javax.sql.DataSource;
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/**
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* web.xml configuration part of the a data source
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*
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* <web-app>
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...
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<resource-ref>
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<description>the database for this app</description>
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<res-ref-name>jdbc/thedatabase</res-ref-name>
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<res-type>javax.sql.DataSource</res-type>
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<res-auth>CONTAINER</res-auth>
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</resource-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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<resource-description>
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<res-ref-name>jdbc/thedatabase</res-ref-name>
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<jndi-name>jdbc/gangland</jndi-name>
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</resource-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 AccessingADataSourceFromAServlet extends HttpServlet {
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public void init() {
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System.out.println( "### loading -> " + getServletName() + " at " +
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new Date( System.currentTimeMillis() ).toString() );
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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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Connection con = null;
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try {
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Context ctx = new InitialContext();
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DataSource ds = (DataSource) ctx.lookup( "java:comp/env/jdbc/thedatabase" );
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con = ds.getConnection();
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Statement stmt = con.createStatement();
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ResultSet rs = stmt.executeQuery( "select * from enemies" );
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while( rs.next() ) {
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pw.println( rs.getString( "name" ) + "<br>" );
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}
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}
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catch( Exception ex ) {
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log( "problem accessing database", ex );
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res.sendError( res.SC_INTERNAL_SERVER_ERROR, ex.getMessage() );
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}
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finally {
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if( con != null ) {
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try {
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con.close();
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}
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catch( SQLException ex ) {
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log( "problem closing connection", ex );
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}
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}
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}
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}
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}
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