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MySQL DBCP example


The reported version numbers of the MySQL and JDBC drivers that work correctly are:

  • MySQL 3.23.47, MySQL 3.23.47 with InnoDB, MySQL 3.23.58, and MySQL 4.0.1 alpha

  • Connector/J 3.0.11-stable (JDBC official driver)

  • mm.mysql 2.0.14 (an older JDBC third-party driver)

Don't forget to copy the JDBC driver JAR file to $CATALINA_HOME/lib before proceeding to the next step.

MySQL configuration

Be sure to follow the instructions below, otherwise problems will occur.

Create a new test user, a new database, and a new test table. A password must be specified for the MySQL user. If the password is empty, then when connecting, it will not be able to drive normally.

mysql> GRANT ALL PRIVILEGES ON *.* TO [email protected]    ->   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: Once the test is over, the user in the example above should be deleted!

Let's insert some test data into the testdata table:

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)

context configuration

Add a resource declaration in the Context to configure the JNDI data source in Tomcat.

Examples are as follows:

    <!-- maxTotal: Maximum number of database connections in pool. Make sure you
         configure your mysqld max_connections large enough to handle
         all of your db connections. Set to -1 for no limit.
    <!-- maxIdle: Maximum number of idle database connections to retain in pool.
         Set to -1 for no limit.  See also the DBCP documentation on this
         and the minEvictableIdleTimeMillis configuration parameter.
    <!-- maxWaitMillis: Maximum time to wait for a database connection to become available
         in ms, in this example 10 seconds. An Exception is thrown if
         this timeout is exceeded.  Set to -1 to wait indefinitely.
 <!-- username and password: MySQL username and password for database connections  -->
    <!-- driverClassName: Class name for the old mm.mysql JDBC driver is
         org.gjt.mm.mysql.Driver - we recommend using Connector/J though.
         Class name for the official MySQL Connector/J driver is com.mysql.jdbc.Driver.
    <!-- url: The JDBC connection url for connecting to your MySQL database.
  <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"

web.xml configuration
Create a WEB-INF/web.xml file for the test application:   

<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
  <description>MySQL Test App</description>
      <description>DB Connection</description>

test code

Create a simple test.jsp page, which will be used later.

<%@ 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>
    <title>DB Test</title>
  <h2>Results</h2><c:forEach var="row" items="${rs.rows}">
    Foo ${row.foo}<br/>
    Bar ${row.bar}<br/></c:forEach>

JSP pages use JSTL's SQL and Core taglibs. You can get it from the Apache Tomcat Taglibs - Standard Tag Library project, but note that it should be version 1.1.x or later. After downloading JSTL, copy jstl.jar and standard.jar into the WEB-INF/lib directory of the web application.

Finally, deploy your application to $CATALINA_BASE/webapps in two ways: either deploy the application as a WAR file called DBTest.war; or place the application in a subdirectory called DBTest.

After the deployment is complete, you can enter http://localhost:8080/DBTest/test.jsp in the browser to view your first labor results.


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