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C3P0踩坑

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我是靠谱客的博主 落后小土豆，最近开发中收集的这篇文章主要介绍C3P0踩坑，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

第一个坑很明显就是找不到数据库，说明你没有database，或者database写错。

com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@7f31c43f -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
6月 25, 2019 4:32:15 下午 com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run

...

java.sql.SQLSyntaxErrorException: Unknown database 'ja'

解决方法就很easy了，检查是不是有以上两个问题，修改即可。

第二个坑也是比较明显的，时区报错，从而引起的c3p0连接数据库失败。

java.sql.SQLException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more than one time zone. You must configure either the server or JDBC 

Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.

Exception in thread "main" java.sql.SQLException: Connections could not be acquired from the underlying database!

Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.

解决办法：连接数据库的url改为

jdbc:mysql://127.0.0.1:3306/javabook?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8

第三个坑,更加明显驱动器的更改了,mysql80以上的版本驱动器改为

com.mysql.cj.jdbc.Driver

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

第四个坑就是数据库服务器没打开，这个坑不是我遇到，但是确实有这样的情况，记录一下。


The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
	at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835)
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
	at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

解决办法，打开数据库服务器,dos窗口管理员模式运行下，运行

net start mysql

第五个坑就是最大的坑了吧

	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:352)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:328)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:301)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:194)
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:65)
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
	at com.sun.proxy.$Proxy20.selectOne(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:166)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:84)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:58)
	at com.sun.proxy.$Proxy22.queryById(Unknown Source)
	at com.li.test.BookTest.testQueryById(BookTest.java:17)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
	at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

解决办法，使用这个jar包
链接：https://pan.baidu.com/s/1itV4ru-qog-yNpIuizgQCQ
提取码：iokd

第六个坑：web项目中的jar包应该放在tomcat的lib文件下，因为tomcat默认使用的是自己的jar包。
如果出现单用没有问题，但是使用tomcat有问题，就应该更新或者增加tomcat中的lib中的jar包

接下来说一说使用的方法
不使用配置文件

import com.mchange.v2.c3p0.ComboPooledDataSource;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;

public class TEST {
    public static void main(String[] args) throws Exception{
//        Class.forName("com.mysql.cj.jdbc.Driver");
//
//        Connection c= DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/javabook?serverTimezone=GMT%2B8&useSSL=false&characterEncoding=UTF-8","root","1230");
//
        ComboPooledDataSource source = new ComboPooledDataSource();
        source.setDriverClass("com.mysql.cj.jdbc.Driver");
        source.setJdbcUrl("jdbc:mysql://127.0.0.1:3306/javabook?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8");
        source.setUser("root");
        source.setPassword("1230");
        source.getConnection();
    }
}

使用C3P0的配置文件
这里有坑，名字一定要为

c3p0-config,xml

并且一定要放在source文件夹下,因为默认会从这个地方找这个文件。

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
  <default-config>
	<property name="driverClass">com.mysql.cj.jdbc.Driver</property>
	<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/javabook?serverTimezone=GMT%2B8&amp;useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf-8</property>
	<property name="user">root</property>
	<property name="password">1230</property>
    <property name="initialPoolSize">10</property>
    <property name="maxIdleTime">30</property>
    <property name="maxPoolSize">100</property>
    <property name="minPoolSize">10</property>
  </default-config>
</c3p0-config>

创建C3P0Utils

package utils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;


import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0Utils {
	
	private static ComboPooledDataSource source  = new ComboPooledDataSource();
	
	public static DataSource getDataSource(){
		return source;
	}
	
	public static Connection getConnection(){
		try {
			return source.getConnection();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			throw new RuntimeException("服务器错误");
		}
	}
	
	public static void closeAll(Connection conn,Statement statement,ResultSet resultSet){
		
		if(resultSet != null){
			try {
				resultSet.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			resultSet = null;
		}
		
		if(statement != null){
			try {
				statement.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			statement = null;
		}
		
		if(conn != null){
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				conn = null;
			}
		}
	}
}

其中的closeAll不是很有必要，可以直接删除

接下来就可以使用QueryRunner进行执行sql，或者使用Statement进行执行sql语句.

  QueryRunner qr = new QueryRunner(C3P0Utils.getDataSource());
        String sql = "INSERT INTO user " +
                "(username,PASSWORD,gender,email,telephone,introduce,activeCode,state,role) " +
                "VALUES (?,?,?,?,?,?,?,?,?)";

        qr.update(sql,"fa","fa","男",
                "fd","15","fd",
               "fd",0,"user");

最后说一下就是tomcat中使用的c3p0时候不应该只把WEB-INF中的libs文件夹中，也应该放在jre 的路径下，就是
eclipse中的

build to path

IDEA中的

Add AS Library

最后

以上就是落后小土豆为你收集整理的C3P0踩坑的全部内容，希望文章能够帮你解决C3P0踩坑所遇到的程序开发问题。

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