A common task faced in development of Java EE applications is to configure a servlet container with the ability to communicate with external data sources, such as a database. To facilitate this connection we will use JDBC via a JNDI specification.
Connection pooling dependencies are located in a single JAR at $CATALINA_HOME/lib/tomcat-dbcp.jar. However, only the classes needed for connection pooling have been included, and the packages have been renamed to avoid interfering with applications.
To include connectivity to external sources, use a connection-specific jdbc driver:
Versions of MySQL and JDBC drivers that have been reported to work:
- MySQL 3.23.47, MySQL 3.23.47 using InnoDB,, MySQL 3.23.58, MySQL 4.0.1alpha
- Connector/J 3.0.11-stable (the official JDBC Driver)
- mm.mysql 2.0.14 (an old 3rd party JDBC Driver)
Place the dependencies needed in CATALINA_HOME/lib/
MySQL DBCP
1. DB configuration
Ensure that you follow these instructions as variations can cause problems.
Create a new test user, a new database and a single test table. Your MySQL user must have a password assigned. The driver will fail if you try to connect with an empty password.
|
1 2 3 4 |
mysql> GRANT ALL PRIVILEGES ON *.* TO javauser@localhost -> IDENTIFIED BY 'javadude' WITH GRANT OPTION; mysql> create database javatest; mysql> use javatest; mysql> create table testdata ( -> id int not null auto_increment primary key, -> foo varchar(25), -> bar int); |
Note: the above user should be removed once testing is complete!
Next insert some test data into the testdata table.
|
1 2 3 4 5 6 7 8 9 |
mysql> insert into testdata values(null, 'hello', 12345); Query OK, 1 row affected (0.00 sec) mysql> select * from testdata; +----+-------+-------+ | ID | FOO | BAR | +----+-------+-------+ | 1 | hello | 12345 | +----+-------+-------+ 1 row in set (0.00 sec) |
|
1 2 3 4 5 6 7 8 9 |
mysql> insert into testdata values(null, 'hello', 12345); Query OK, 1 row affected (0.00 sec) mysql> select * from testdata; +----+-------+-------+ | ID | FOO | BAR | +----+-------+-------+ | 1 | hello | 12345 | +----+-------+-------+ 1 row in set (0.00 sec) |
2. Context configuration
Configure the JNDI DataSource in Tomcat by adding a declaration for your resource to your Context.
For example:
|
1 2 3 4 5 6 |
<Context> <Resource name="jdbc/TestDB" auth="Container" type="javax.sql.DataSource" maxTotal="100" maxIdle="30" maxWaitMillis="10000" username="javauser" password="javadude" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/javatest"/> </Context> |
3. web.xml configuration
Now create a WEB-INF/web.xml for this test application.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 |
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> <description>MySQL Test App</description> <resource-ref> <description>DB Connection</description> <res-ref-name>jdbc/TestDB</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> </web-app> |
4. Test code
Now create a simple test.jsp page for use later.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 |
<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %> <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> <sql:query var="rs" dataSource="jdbc/TestDB"> select id, foo, bar from testdata </sql:query> <html> <head> <title>DB Test</title> </head> <body> <h2>Results</h2> <c:forEach var="row" items="${rs.rows}"> Foo ${row.foo}<br/> Bar ${row.bar}<br/> </c:forEach> </body> </html> |
That JSP page makes use of JSTL‘s SQL and Core taglibs. You can get it from Apache Tomcat Taglibs – Standard Tag Library project — just make sure you get a 1.1.x or later release. Once you have JSTL, copy jstl.jar and standard.jar to your web app’s WEB-INF/lib directory.
Finally deploy your web app into $CATALINA_BASE/webapps either as a warfile called DBTest.war or into a sub-directory called DBTest
Once deployed, point a browser at http://localhost:8080/DBTest/test.jsp to view the fruits of your hard work.
Oracle 8i, 9i & 10g
0. Introduction
Oracle requires minimal changes from the MySQL configuration except for the usual gotchas 🙂
Drivers for older Oracle versions may be distributed as *.zip files rather than *.jar files. Tomcat will only use *.jar files installed in $CATALINA_HOME/lib. Therefore classes111.zip or classes12.zip will need to be renamed with a .jar extension. Since jarfiles are zipfiles, there is no need to unzip and jar these files – a simple rename will suffice.
For Oracle 9i onwards you should use oracle.jdbc.OracleDriver rather than oracle.jdbc.driver.OracleDriver as Oracle have stated that oracle.jdbc.driver.OracleDriver is deprecated and support for this driver class will be discontinued in the next major release.
1. Context configuration
In a similar manner to the mysql config above, you will need to define your Datasource in your Context. Here we define a Datasource called myoracle using the thin driver to connect as user scott, password tiger to the sid called mysid. (Note: with the thin driver this sid is not the same as the tnsname). The schema used will be the default schema for the user scott.
Use of the OCI driver should simply involve a changing thin to oci in the URL string.
|
1 2 |
<Resource name="jdbc/myoracle" auth="Container" type="javax.sql.DataSource" driverClassName="oracle.jdbc.OracleDriver" url="jdbc:oracle:thin:@127.0.0.1:1521:mysid" username="scott" password="tiger" maxTotal="20" maxIdle="10" maxWaitMillis="-1"/> |
2. web.xml configuration
You should ensure that you respect the element ordering defined by the DTD when you create you applications web.xml file.
|
1 2 3 4 5 6 |
<resource-ref> <description>Oracle Datasource example</description> <res-ref-name>jdbc/myoracle</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> |
3. Code example
You can use the same example application as above (asuming you create the required DB instance, tables etc.) replacing the Datasource code with something like
|
1 2 3 4 |
Context initContext = new InitialContext(); Context envContext = (Context)initContext.lookup("java:/comp/env"); DataSource ds = (DataSource)envContext.lookup("jdbc/myoracle"); Connection conn = ds.getConnection(); |
PostgreSQL
0. Introduction
PostgreSQL is configured in a similar manner to Oracle.
1. Required files
Copy the Postgres JDBC jar to $CATALINA_HOME/lib. As with Oracle, the jars need to be in this directory in order for DBCP’s Classloader to find them. This has to be done regardless of which configuration step you take next.
2. Resource configuration
You have two choices here: define a datasource that is shared across all Tomcat applications, or define a datasource specifically for one application.
2a. Shared resource configuration
Use this option if you wish to define a datasource that is shared across multiple Tomcat applications, or if you just prefer defining your datasource in this file.
This author has not had success here, although others have reported so. Clarification would be appreciated here.
|
1 2 3 4 |
<Resource name="jdbc/postgres" auth="Container" type="javax.sql.DataSource" driverClassName="org.postgresql.Driver" url="jdbc:postgresql://127.0.0.1:5432/mydb" username="myuser" password="mypasswd" maxTotal="20" maxIdle="10" maxWaitMillis="-1"/> |
2b. Application-specific resource configuration
Use this option if you wish to define a datasource specific to your application, not visible to other Tomcat applications. This method is less invasive to your Tomcat installation.
Create a resource definition for your Context. The Context element should look something like the following.
|
1 2 3 4 5 6 7 8 |
<Context> <Resource name="jdbc/postgres" auth="Container" type="javax.sql.DataSource" driverClassName="org.postgresql.Driver" url="jdbc:postgresql://127.0.0.1:5432/mydb" username="myuser" password="mypasswd" maxTotal="20" maxIdle="10" maxWaitMillis="-1"/> </Context> |
3. web.xml configuration
|
1 2 3 4 5 6 |
<resource-ref> <description>postgreSQL Datasource example</description> <res-ref-name>jdbc/postgres</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> |
4. Accessing the datasource
When accessing the datasource programmatically, remember to prepend java:/comp/env to your JNDI lookup, as in the following snippet of code. Note also that “jdbc/postgres” can be replaced with any value you prefer, provided you change it in the above resource definition file as well.
|
1 2 3 4 5 6 7 8 9 10 |
InitialContext cxt = new InitialContext(); if ( cxt == null ) { throw new Exception("Uh oh -- no context!"); } DataSource ds = (DataSource) cxt.lookup( "java:/comp/env/jdbc/postgres" ); if ( ds == null ) { throw new Exception("Data source not found!"); } |
