Note 对于Tomcat4和5，postgresql.jar必须放在$CATALINA_HOME/common/lib中

    绝对轻松的办法是把它设置在Tomcat一起提供的Tomcat实例admin web应用中，只需把数据源家到你要用到的Context中即可。

    下面是在Tomcat 4的conf/server.xml中标签中的设置<>

<Resource name="jdbc/postgres" scope="Shareable" type="javax.sql.DataSource"/> <ResourceParams name="jdbc/postgres">   <parameter>     <name>validationQuery</name>     <value>select version();</value>   </paramete>   <parameter>     <name>url</name>     <value>jdbc:postgresql://localhost/davec</value>   </parameter>   <parameter>     <name>password</name>     <value>davec</value>   </parameter>   <parameter>     <name>maxActive</name>     <value>4</value>   </parameter>   <parameter>     <name>maxWait</name>     <value>5000</value>   </parameter>   <parameter>     <name>driverClassName</name>     <value>org.postgresql.Driver</value>   </parameter>   <parameter>     <name>username</name>     <value>davec</value>   </parameter>   <parameter>     <name>maxIdle</name>     <value>2</value>   </parameter> </ResourceParams>

    在Tomcat 5中设置可以用以上方法，只是它变成是标签中的，如.....

    另外，还有一个conf/Catalina/hostname/context.xml的文件。例如，http://localhost:8080/servlet-example目录中有一个文件 $CATALINA_HOME/conf/Catalina/localhost/servlet-example.xml。这个文件里面把上面的xml放置在标签中。

    然后你可以用以下代码访问连接。

import javax.naming.*; import javax.sql.*; import java.sql.*; public class DBTest {     String foo = "Not Connected";     int bar = -1;     public void init() {         try {             Context ctx = new             InitialContext();             if(ctx == null )                throw new Exception("Boom - No Context"); // /jdbc/postgres is the name of the resource above                 DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/postgres");                 if (ds != null) {                         Connection conn = ds.getConnection();                         if(conn != null) {                             foo = "Got Connection "+conn.toString();                             Statement stmt = conn.createStatement();                             ResultSet rst = stmt.executeQuery("select id, foo, bar from testdata");                             if(rst.next()) {                             foo=rst.getString(2);                             bar=rst.getInt(3);                         }                         conn.close();                     }                 } catch(Exception e) {                      e.printStackTrace();                 }             }     public String getFoo() {         return foo;     }     public int getBar() {         return bar;     } }