IDEA从零到精通（12）之用C3P0连接Mysql数据库
Posted 编程界明世隐
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作者简介
作者名：编程界明世隐
简介：CSDN博客专家，从事软件开发多年，精通Java、javascript，博主也是从零开始一步步把学习成长、深知学习和积累的重要性，喜欢跟广大ADC一起打野升级，欢迎您关注，期待与您一起学习、成长、起飞！
引言
我本来是一直用eclipse和myeclipse的老程序员了，很多我的粉丝小伙伴都说他们要用idea，问我怎么不用idea，其实明哥觉得用啥开发工具都不是重点，重点是要跟着明哥多学Java知识、多练习，但是作为一个宠粉的人，我怎么能拒绝粉丝的要求呢，于是我偷偷的去学习了一波（拿来吧你），然后就写了这个系列，希望小伙伴们能有所收获，明哥会努力更新的。
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一、下载驱动并加入项目中
- 网上下载Mysql jar包和c3p0的jar包（总共有3个），需要jar包的可以到公众号“编程界明世隐”，回复：“mysql驱动”，下载这几个jar包
打开项目，依次打开目录，web–WEB-INF–lib 加入这几个驱动jar包。
我的jar包名称如下：
mchange-commons-java-0.2.3.4.jar
mysql-connector-java-5.0.8-bin.jar
c3p0-0.9.2.1.jar
- 引入jar包到项目中
File – Project Structure… – Libraies
点击“加号” – Java
选择好你项目中lib下的驱动jar包，点击OK
加入后效果图如下，点击OK
- c3p0 jar包引入方式和mysql一样。
还有mchange-commons-java jar包
二、编写配置文件
在src下放入xml配置：c3p0-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<!--
C3P0的缺省(默认)配置，
如果在代码中“ComboPooledDataSource ds = new ComboPooledDataSource();”这样写就表示使用的是C3P0的缺省(默认)配置信息来创建数据源
-->
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/library?characterEncoding=utf8</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="acquireIncrement">5</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">5</property>
<property name="maxPoolSize">20</property>
</default-config>
<!--
C3P0的命名配置，
如果在代码中“ComboPooledDataSource ds = new ComboPooledDataSource("MySQL");”这样写就表示使用的是name是MySQL的配置信息来创建数据源
-->
<named-config name="MySQL">
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/library?characterEncoding=utf8</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="acquireIncrement">5</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">5</property>
<property name="maxPoolSize">20</property>
</named-config>
</c3p0-config>
三、编写工具类
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class C3P0_Utils
private static ComboPooledDataSource dataSource = null;
//在静态代码块中创建数据库连接池
static
try
dataSource = new ComboPooledDataSource("MySQL");//使用C3P0的命名配置来创建数据源
System.out.println(dataSource);
catch (Exception e)
throw new ExceptionInInitializerError(e);
public static Connection getConnection() throws SQLException
//从数据源中获取数据库连接
return dataSource.getConnection();
// 释放资源
public static void release(Connection conn,Statement st,ResultSet rs)
if(rs!=null)
try
//关闭存储查询结果的ResultSet对象
rs.close();
catch (Exception e)
e.printStackTrace();
rs = null;
if(st!=null)
try
//关闭负责执行SQL命令的Statement对象
st.close();
catch (Exception e)
e.printStackTrace();
if(conn!=null)
try
//将Connection连接对象还给数据库连接池
conn.close();
catch (Exception e)
e.printStackTrace();
四、编写测试类
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
public class DataSourceTest
public void c3p0DataSourceTest()
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try
//获取数据库连接
conn = C3P0_Utils.getConnection();
String sql = "select * from user"; // 查询数据的sql语句
st = (Statement) conn.createStatement(); //创建用于执行静态sql语句的Statement对象，st属局部变量
rs = st.executeQuery(sql); //执行sql查询语句，返回查询数据的结果集
System.out.println("最后的查询结果为：");
while (rs.next()) // 判断是否还有下一个数据
// 根据字段名获取相应的值
String name = rs.getString("name");
String no = rs.getString("no");
//输出查到的记录的各个字段的值
System.out.println("名字：" + name + "，账号 " + no);
catch (Exception e)
e.printStackTrace();
finally
//释放资源
C3P0_Utils.release(conn, st, rs);
public static void main(String[] args)
new DataSourceTest().c3p0DataSourceTest();
五、测试运行
可以在最后几行的位置看到查询结果。
MLog clients using log4j logging.
Initializing c3p0-0.9.2.1 [built 20-March-2013 11:16:28 +0000; debug? true; trace: 10]
MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=1okythyak1w154khck75wa|bebdb06,name=1okythyak1w154khck75wa|bebdb06 registered.
MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=1okythyak1w154khck75wa|bebdb06,name=1okythyak1w154khck75wa|bebdb06 unregistered, in order to be reregistered after update.
MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=1okythyak1w154khck75wa|bebdb06,name=1okythyak1w154khck75wa|bebdb06 registered.
MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=1okythyak1w154khck75wa|bebdb06,name=1okythyak1w154khck75wa|bebdb06 unregistered, in order to be reregistered after update.
MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=1okythyak1w154khck75wa|bebdb06,name=MySQL registered.
com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 5, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> MySQL, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1okythyak1w154khck75wa|bebdb06, idleConnectionTestPeriod -> 0, initialPoolSize -> 10, jdbcUrl -> jdbc:mysql://localhost:3306/library?characterEncoding=utf8, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 5, numHelperThreads -> 3, preferredTestQuery -> null, properties -> user=******, password=******, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> , usesTraditionalReflectiveProxies -> false ]
Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 5, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> MySQL, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1okythyak1w154khck75wa|bebdb06, idleConnectionTestPeriod -> 0, initialPoolSize -> 10, jdbcUrl -> jdbc:mysql://localhost:3306/library?characterEncoding=utf8, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 5, numHelperThreads -> 3, preferredTestQuery -> null, properties -> user=******, password=******, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, userOverrides -> , usesTraditionalReflectiveProxies -> false ]
incremented pending_acquires: 1
Starting acquisition series. Incremented pending_acquires [1], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@5fe5c6f
incremented pending_acquires: 2
Starting acquisition series. Incremented pending_acquires [2], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@6979e8cb
incremented pending_acquires: 3
Starting acquisition series. Incremented pending_acquires [3], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@763d9750
incremented pending_acquires: 4
Starting acquisition series. Incremented pending_acquires [4], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@5c0369c4
incremented pending_acquires: 5
Starting acquisition series. Incremented pending_acquires [5], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@2be94b0f
incremented pending_acquires: 6
Starting acquisition series. Incremented pending_acquires [6], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@d70c109
incremented pending_acquires: 7
Starting acquisition series. Incremented pending_acquires [7], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@17ed40e0
incremented pending_acquires: 8
Starting acquisition series. Incremented pending_acquires [8], attempts_remaining: 30
com.mchange.v2.async.ThreadPoolAsynchronousRunner@2471cca7: Adding task to queue -- com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@50675690
incremented pending_acquires: 9
Starting acquisition series. Incremented pending_acquires [9], attempts_remaining: 30
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