Thursday, April 1, 2010

DataSource in Jetty through JNDI

Prerequesite: Please ensure JNDI is configured properly and you can pass parameters to Jetty via JNDI.

First, you need to add the used libraries to Jettys classpath. In my case, I wanted commons-dbcp (alternative: c3p0) over an H2 database, so I added the following to my pom.xml


      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>7.0.1.v20091125</version>
        <dependencies>
          <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>1.4</version>
          </dependency>
          <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.2.131</version>
          </dependency>
        </dependencies>
      </plugin>

On Jetty standalone, I copied the libraries to the lib/ext directory and added ext to the options in start.ini. Please note that commons-dbcp also requires commons-pool.

Next, add the configuration of your DataSource to jetty-env.xml:


<?xml version="1.0"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://jetty.mortbay.org/configure.dtd">
<Configure id="thisfile" class="org.eclipse.jetty.webapp.WebAppContext">
  <New class="org.eclipse.jetty.plus.jndi.Resource">
    <Arg><Ref id="thisfile"/></Arg>
    <Arg>jdbc/nameOfMyDatabase</Arg>
    <Arg>
      <New class="org.apache.commons.dbcp.BasicDataSource">
        <Set name="url">jdbc:h2:/path/to/your/DataBase</Set>
      </New>
    </Arg>
  </New>
</Configure>

To actually have access to the datasource, you also need modify web.xml to declare that you want a resource unter this name:


  <resource-ref>
    <res-ref-name>jdbc/nameOfMyDatabase</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
  </resource-ref>

The database is now available as DataSource at java:/comp/env/jdbc/nameOfMyDatabase and can be used directly in tools such as hibernate by setting hibernate.connection.datasource to this value.

Background: Hibernate did not properly release the database connection when the WebApp shut down. This resulted in Exceptions when trying to undeploy and deploy the webapp without killing Jetty, as the embedded database existed both in the old and the new context. By moving the connection out of the WebApp, and into Jetty's responsibility, the embedded database driver now only exists in Jetty's context. Adding the connection pool is just decoration.

1 comment:

  1. The Java Code to Test Above using the Proper Context is:

    Context initCtx = null;
    DataSource ds = null;
    try {
    initCtx = new InitialContext();
    ds = (DataSource)initCtx.lookup("java:/comp/env/jdbc/nameOfMyDatabase");
    } catch (NamingException e) {
    e.printStackTrace();
    }

    System.out.println("Creating DS one.");
    Connection conn = ds.getConnection();
    System.out.println(conn.getMetaData());
    System.out.println("Creating statement.");
    stmt = conn.createStatement();
    System.out.println("Executing statement.");
    rset = stmt.executeQuery("Select * from DUAL");
    System.out.println("Results:");

    ReplyDelete

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