配置c3p0数据源的时候提示的错误

最新推荐文章于 2025-03-17 21:59:45 发布

mtcurry

最新推荐文章于 2025-03-17 21:59:45 发布

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分类专栏： Javaweb jdbc c3p0 文章标签： c3p0 javaweb 空指针异常多个数据源

本文链接：https://blog.youkuaiyun.com/mtcurry/article/details/51997359

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在学习配置c3p0数据源时遇到了ClassNotFoundException和空指针异常，这些问题分别由于缺少mchange-commons-java-0.2.3.4.jar库和XML配置错误引起。解决方案包括添加缺失的jar文件到lib目录，修正XML配置中的标签拼写。另外，还介绍了如何在c3p0中配置多个数据源。

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最近自己在学习的过程中，需要配置c3p0数据源，于是按照网上的教程进行配置，中间无疑会遇到很多错误，挑选几个重要的进行说明

1，java.lang.ClassNotFoundException: com.mchange.v2.ser.Indirector ，空指针异常，

解决办法：这个错误出现的原因是缺少mchange-commons-java-0.2.3.4.jar 文件导致的，读者可以将该文件放在WEB-INF/lib文件下即可

2.提示

java.lang.NullPointerException
	at com.mysql.fabric.jdbc.FabricMySQLDriver.parseFabricURL(FabricMySQLDriver.java:97)
	at com.mysql.fabric.jdbc.FabricMySQLDriver.acceptsURL(FabricMySQLDriver.java:93)
	at java.sql.DriverManager.getDriver(Unknown Source)
	at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:240)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:131)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:156)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:145)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
	at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)

这个的原因，我这里是因为配置的时候，本来应该是<named-config>,我写成了<name-config>

3.此外，我们可以在配置c3p0的时候指定多个数据源，在实例化数据源的时候通过name属性指定，废话少说，上代码

c3p0-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
	<!-- This is default config! -->
	<default-config>
		<property name="initialPoolSize">10</property>
		<property name="maxIdleTime">30</property>
		<property name="maxPoolSize">100</property>
		<property name="minPoolSize">10</property>
		<property name="maxStatements">200</property>
		<property name="acquireIncrement">10</property>
	</default-config>

	<named-config name="mysql">
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql://localhost:3306/file</property>
		<property name="user">root</property>
		<property name="password"></property>
		<property name="initialPoolSize">10</property>
		<property name="maxIdleTime">30</property>
		<property name="maxPoolSize">100</property>
		<property name="minPoolSize">10</property>
		<property name="maxStatements">200</property>
		<property name="acquireIncrement">10</property>
	</named-config>
	
	<named-config name="oracle">
		<property name="driverClass">oracle.jdbc.driver.OracleDriver</property>
		<property name="jdbcUrl">jdbc:oracle:thin:@localhost:1521:l</property>
		<property name="user"></property>
		<property name="password"></property>

<pre name="code" class="html"><span style="white-space:pre">		</span><property name="initialPoolSize">10</property>
		<property name="maxIdleTime">30</property>
		<property name="maxPoolSize">100</property>
		<property name="minPoolSize">10</property>
		<property name="maxStatements">200</property>
		<property name="acquireIncrement">10</property>

</named-config></c3p0-config>

然后是c3p0数据源的控制类

package com.practice.javaweb.fileupload.db;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0Utils {

	private static ComboPooledDataSource c3p0DataSource;
	static {
		c3p0DataSource = new ComboPooledDataSource("mysql");
	}

	/**
	 * 获取数据库连接
	 * 
	 * @return
	 */
	public static Connection getConnection() {
		Connection connection = null;
		try {
			connection = c3p0DataSource.getConnection();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return connection;
	}

	/**
	 * 
	 * 关闭连接
	 * 
	 * @param connection
	 * @param preparedStatement
	 * @param resultSet
	 */
	public static void close(Connection connection,
			PreparedStatement preparedStatement, ResultSet resultSet) {
		if (resultSet != null) {
			try {
				resultSet.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if (preparedStatement != null) {
			try {
				preparedStatement.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if (connection != null) {
			try {
				connection.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	public static void main(String[] args) {
		Connection conn = getConnection();
		System.out.println(conn.getClass().getName());
		close(conn, null, null);
	}
}