Tomcat7 JDBC 池

Question

我在 META-INF 中有以下内容

<Context>
   <Resource type="javax.sql.DataSource"
        name="jdbc/TestDB"
        factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
        driverClassName="com.mysql.jdbc.Driver"
        url="jdbc:mysql://localhost:3306/"
        username="mysql_user"
        password="mypassword123"/>
</Context>

在我的 web.xml 中有

<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>

在我的 Java 代码中，我有

Context initContext = new InitialContext();
Context envContext  = (Context)initContext.lookup("java:/comp/env");
DataSource datasource = (DataSource)envContext.lookup("jdbc/TestDB");
con = datasource.getConnection();

当 Tomcat 启动时，我收到以下错误，并且我的 libs 文件夹中有 mysql-connector-java-5.1.20-bin.jar。知道为什么吗？

INFO: Starting Servlet Engine: Apache Tomcat/7.0.27
05-Jun-2012 23:16:29 org.apache.naming.NamingContext lookup
WARNING: Unexpected exception resolving reference
java.sql.SQLException: com.mysql.jdbc.Driver
at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:242)
at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:175)
at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:684)
at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:616)
at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:479)
at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:135)
at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:114)
at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:101)
at org.apache.tomcat.jdbc.pool.DataSourceFactory.createDataSource(DataSourceFactory.java:501)
at org.apache.tomcat.jdbc.pool.DataSourceFactory.getObjectInstance(DataSourceFactory.java:224)
at org.apache.naming.factory.ResourceFactory.getObjectInstance(ResourceFactory.java:143)
at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304)
at org.apache.naming.NamingContext.lookup(NamingContext.java:843)
at org.apache.naming.NamingContext.lookup(NamingContext.java:154)
at org.apache.naming.NamingContext.lookup(NamingContext.java:831)
at org.apache.naming.NamingContext.lookup(NamingContext.java:168)
at org.apache.catalina.core.NamingContextListener.addResource(NamingContextListener.java:1061)
at org.apache.catalina.core.NamingContextListener.createNamingContext(NamingContextListener.java:671)
at org.apache.catalina.core.NamingContextListener.lifecycleEvent(NamingContextListener.java:270)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5161)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1566)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1556)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:235)
... 29 more

Answer 1

我在 Ubuntu 上通过 apt-get 机制安装了 Tomcat7 时遇到了这个问题。问题是 Tomcat 使用的 dbcp，更具体地说是 commons-dbcp.jar 而不是 tomcat-dbcp.jar。

为了解决这个问题，我从 tomcat 站点下载的 Tomcat7 副本中提取了catalina*.jar 和tomcat-dbcp.jar，并替换了 tomcat 的 lib 文件夹中的文件。 （commons-dbcp.jar 替换为tomcat-dbcp.jar）。

见this link。

Answer 2

您缺少 MySQL 的 JDBC 驱动程序。

从 MySQL 的网站下载它们：http://dev.mysql.com/downloads/connector/j/

将驱动程序添加到您的类路径、项目或 Tomcat 的 HOME\lib 目录。