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c3p0详细配置

西瓜 — Wed, 16 Mar 2011 02:31:00 GMT

官方文档 : http://www.mchange.com/projects/c3p0/index.html

3

30

1000

false

Test

false

100

null

60

3

60

15

100

3

root

password

select id from test where id=1

300

false

true

root

false

con_test
30000
30
10
30
25
10
0

200

300

转：http://www.wujianrong.com/archives/2007/08/c3p0.html

解决MYSQL 8��时问题

最�q�的一个项目在Hibernate使用C3P0的连接池�Q�数据库为Mysql。开发测试没有问题，在运行中每个一�D�长的空闲时间就出现异常:

java 代码

org.hibernate.exception.JDBCConnectionException: could not execute query
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java: 74 )
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java: 43 )
.......
Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed due to underlying exception/error:
** BEGIN NESTED EXCEPTION **
com.mysql.jdbc.CommunicationsException
MESSAGE: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.net.SocketException
MESSAGE: Broken pipe
STACKTRACE:
java.net.SocketException: Broken pipe
at java.net.SocketOutputStream.socketWrite0(Native Method)
......
** END NESTED EXCEPTION **

查看了Mysql的文档，以及Connector/J的文档以及在�U�说明发玎ͼ�出现�q�种异常的原因是�Q?/p>

Mysql服务器默认的“wait_timeout”�?��时�Q�也��是说一个connection�I�闲��过8个小�Ӟ��Mysql��自动断开�? connection。这��是问题的所在，在C3P0 pools中的connections如果�I�闲��过8��时�Q�Mysql��其断开�Q�而C3P0�q�不知道该connection已经失效�Q�如果这时有 Client��h��connection�Q�C3P0��该失效的Connection提供�l�Client�Q�将会造成上面的异常�?/p>

解决的方法有3�U�：

增加wait_timeout的时间�?
减少Connection pools中connection的lifetime�?
��试Connection pools中connection的有效性�?

当然最好的办法是同时综合��用上�q?�U�方法，下面��DBCP和C3P0分别做一说明�Q�假设wait_timeout为默认的8��时

DBCP增加以下配置信息:

//set to 'SELECT 1'
validationQuery = "SELECT 1"
//set to 'true'
testWhileIdle = "true"
//some positive integer
timeBetweenEvictionRunsMillis = 3600000
//set to something smaller than 'wait_timeout'
minEvictableIdleTimeMillis = 18000000
//if you don't mind a hit for every getConnection(), set to "true"
testOnBorrow = "true"

C3P0增加以下配置信息:

//获取connnection时测试是否有�?/span>
testConnectionOnCheckin = true
//自动��试的table名称
automaticTestTable=C3P0TestTable
//set to something much less than wait_timeout, prevents connections from going stale
idleConnectionTestPeriod = 18000
//set to something slightly less than wait_timeout, preventing 'stale' connections from being handed out
maxIdleTime = 25000
//if you can take the performance 'hit', set to "true"
testConnectionOnCheckout = true

更多的配�|�信息大家可以查看C3P0文档�Q�Connector/J文档�Q�以及DBCP的文档�?/p>

�? http://www.javaeye.com/article/38506

我自��q��配置:

jdbc.driverClass=com.mysql.jdbc.Driver
jdbc.jdbcUrl = jdbc:mysql://localhost:3306/test
jdbc.user = root
jdbc.password = 12345
jdbc.miniPoolSize = 1
jdbc.maxPoolSize = 20
jdbc.initialPoolSize = 1
jdbc.maxIdleTime = 25000
jdbc.acquireIncrement = 1

jdbc.acquireRetryAttempts = 30
jdbc.acquireRetryDelay = 1000
jdbc.testConnectionOnCheckin = true
jdbc.automaticTestTable = c3p0TestTable
jdbc.idleConnectionTestPeriod = 18000
jdbc.checkoutTimeout=3000

+++++++++++

报错误：
APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!

一般设�|�maxStatements=0解决该问�?
但是�Q?
把max_statements讄��?�?
c3p0在同时关闭statement和connection的时候，或者关闭他们之间的旉��很短的时候，有时候connection�q�没有被关闭�Q�因为有些preparedstatement�q�在被cached住。这是c3p0的作者自��p��的�?
http://forum.hibernate.org/viewtopic.php?t=947246&highlight=apparent+deadlock+c3p0

C3P0增加以下配置信息:

//set to 'SELECT 1'
preferredTestQuery = 'SELECT 1'
//set to something much less than wait_timeout, prevents connections from going stale
idleConnectionTestPeriod = 18000
//set to something slightly less than wait_timeout, preventing 'stale' connections from being handed out
maxIdleTime = 25000
//if you can take the performance 'hit', set to "true"
testConnectionOnCheckout = true

A c3p0 pool with the settings you have should recover from a database reset, but that doesn't mean you will never see an Exception. Stale Connections from the old database session will still be broken, and if those Connections have already been checked out, or if they are in the pool and not tested on checkout, the application will see the broken Connection, in the form of an Exception.

You can use c3p0 to minimize the likelihood that your application will see a stale Connection on database shutdown/restart. The most reliable means of preventing this is to set hibernate.c3p0.validate to true (in a hibernate application -- all other c3p0 apps should use the c3p0-native property c3p0.testConnectionOnCheckout). If you set this property to true, c3p0 will test Connections prior to checkout, and your app will never see a stale Connection on database restart unless the Connection had already been checked out when the database went down.

Another less reliable, but potentially less expensive, strategy is to set c3p0.testConnectionsOnCheckin and hibernate.c3p0.idle_test_period (c3p0-native c3p0.idleConnectionTestPeriod) to a low value, in which case all connection tests are asynchronous and you are guanteed that no Connection will be checked out that hasn't been tested in the last idle_test_period seconds. Thus, your app will only see broken Connections from the pool if Connections are checked out during a short window of time.

In either case, I recommend setting "c3p0.preferredTestQuery " or "c3p0.automaticTestTable" in your c3p0 properties file, as c3p0's default Connection test is often slow.

See "Configuring Connection Testing" in c3p0's docs for more information.

�? 使用c3p0作�ؓ�q�接池时�Q�其中的一些配�|�参数需要修攏V��主要是maxIdleTime和idleConnectionTestPeriod�? MySQL默认�?��时�Q?8800�U�）后自动关闭已打开的连接，所以c3p0要在8��时内关闭不使用的连接，上面�?参数要小�?8800�U�。附上在 hibernate中配�|�c3p0的关键字�?

c3p0-native property name hibernate configuration key
c3p0.acquireIncrement hibernate.c3p0.acquire_increment
c3p0.idleConnectionTestPeriod hibernate.c3p0.idle_test_period
c3p0.initialPoolSize not available -- uses minimum size
c3p0.maxIdleTime hibernate.c3p0.timeout
c3p0.maxPoolSize hibernate.c3p0.max_size
c3p0.maxStatements hibernate.c3p0.max_statements
c3p0.minPoolSize hibernate.c3p0.min_size

转蝲自：http://handawei.javaeye.com/blog/651046

西瓜 2011-03-16 10:31 发表评论

C3P0在spring中的配置

西瓜 — Mon, 09 Aug 2010 02:30:00 GMT

�|�上关于C3P0在spring中的配置�Q�几乎没有完全正��的�Q?br />

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"    destroy-method="close">
          <property name="driverClass"><value>${jdbc.driverClassName}value>property>
          <property name="jdbcUrl"><value>${jdbc.url}value>property>
          <property name="user"><value>${jdbc.username}value>property>
          <property name="password"><value>${jdbc.password}value>property>

          <property name="minPoolSize"><value>1value>property>
          <property name="maxPoolSize"><value>20value>property>
          <property name="maxIdleTime"><value>1800value>property>
          <property name="acquireIncrement"><value>2value>property>
          <property name="maxStatements"><value>0value>property>
          <property name="initialPoolSize"><value>2value>property>
          <property name="idleConnectionTestPeriod"><value>1800value>property>
          <property name="acquireRetryAttempts"><value>30value>property>
          <property name="breakAfterAcquireFailure"><value>truevalue>property>
          <property name="testConnectionOnCheckout"><value>falsevalue>property>
bean>

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
   <property name="dataSource" ref="dataSource"/>
   <property name="mappingDirectoryLocations">
       <list>
    <value>classpath:/com/licaionline/domain/value>
       list>
   property>
   <property name="hibernateProperties">
    <props>
     <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialectprop>
      <prop key="hibernate.show_sql">trueprop>
     <prop key="hibernate.generate_statistics">trueprop>
                 <prop key="hibernate.connection.release_mode">autoprop>
                 <prop key="hibernate.autoReconnect">trueprop>
                 <prop key="hibernate.cglib.use_reflection_optimizer">trueprop>
    props>
   property>
bean>

西瓜 2010-08-09 10:30 发表评论

JDBC的作用及重要接口

西瓜 — Tue, 13 Oct 2009 14:38:00 GMT

摘要: JDBC是由一�p�d��q�接�Q�Connection�Q�、SQL语句�Q�Statement�Q�和�l�果集（ResultSet�Q�构成的�Q�其主要作用概括��h��有如�?个方面：建立与数据库的连接�? 向数据库发�v查询��h��? 处理数据库返... 阅读全文

西瓜 2009-10-13 22:38 发表评论

JAVA调用Oracle存储�q�程

西瓜 — Fri, 22 May 2009 08:19:00 GMT

一、JAVA调用Oracle存储�q�程

　　JAVA跟Oracle之间最常用的是JAVA调用Oracle的存储过�E�，以下��要说明下JAVA如何对Oracle存储�q�程�q�行调用�?/p>

　　Ⅰ、不带输出参数情�?/p>

　　�q�程名称为pro1�Q�参��C��?个，数据�c�d��为整形数�?/p>

import　java.sql. * ; public　 class　ProcedureNoArgs　 { public　 static　 void　main(String args[])　throws　Exception { // 加蝲Oracle驱动　 DriverManager.registerDriver( new　oracle.jdbc.driver.OracleDriver()); // 获得Oracle数据库连接　 Connection conn = DriverManager.getConnection( " jdbc:oracle:thin:@MyDbComputerNameOrIP:1521:ORCL", sUsr, sPwd " ); // 创徏存储�q�程的对象　 CallableStatement c = conn.divpareCall( " {call pro1(?)} " ); // �l�Oracle存储�q�程的参数设�|��?�Q�将�W�一个参数的��D��|�成188　 c.setInt( 1 , 188 ); // 执行Oracle存储�q�程　 c.execute(); conn.close(); }　 }　

　　Ⅱ、带输出参数的情�?/p>

　　�q�程名称为pro2�Q�参��C��?个，数据�c�d��为整形数据，�q�回��gؓ整�Ş�c�d��

import java.sql.*; public class ProcedureWithArgs　 { public static void main(String args[]) throws Exception { //加蝲Oracle驱动 DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver()); //获得Oracle数据库连�?br /> Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@MyDbComputerNameOrIP:1521:ORCL", sUsr, sPwd "); //创徏Oracle存储�q�程的对象，调用存储�q�程 CallableStatement c=conn.divpareCall("{call pro2(?,?)}"); //�l�Oracle存储�q�程的参数设�|��?�Q�将�W�一个参数的��D��|�成188 c.setInt(1,188); //注册存储�q�程的第二个参数　 c.registerOutParameter(2,java.sql.Types.INTEGER); //执行Oracle存储�q�程 c.execute(); //得到存储�q�程的输出参数值�ƈ打印出来 System.out.println (c.getInt(2));　 conn.close(); } } 二，使用JAVA创徏Oracle存储�q�程

　　先看下如何��用JAVA来编写Oracle存储�q�程�Q�我们在Oracle的sql plus中编写语句�?/p>

　　Ⅰ、启动SQL PLUS

　　Ⅱ、编写JAVA�c�，定义JAVA�c�d��名，本存储过�E��ؓ��单地输出传入参数的��^方倹{�?/p>

　create or replace and compile java source named　"PF"　as /** *通过JAVA�c�L�� 创徏Oracle存储�q�程 * **/ package　org.oraclejava.pro; public　 class　javaCreatePro { public　 static　 String　test( int num) { return　num+ "的��^方�ؓ�Q?" +num*num; } }

　　Ⅲ、将JAVA�c�M��的方法test创徏��Z��个Oracle函数�Ҏ(gu��)��

　　create or replace function PF_FUN(name integer) return varchar2 as language java name 'org.oraclejava.pro.javaCreatePro.test(java.lang.Integer) return java.lang.String';

　　Ⅳ、在控制台直接调用创建的Oracle函数

　　select PF_FUN(10) from dual;

　　Ⅴ、输出结�?/p>

　　10的��^方�ؓ�Q?00

　　以上��x��在Oracle中的SQL PLUS中��用JAVA�E�序来��生Oracle存储�q�程的演�C�Z��子，演示了其基本语法的实现跟��单的功能实现�Q�可以看出在JAVA跟Oracle之间存在很多有趣的用法，因�ؓoracle中有java虚拟机，使得Oracle变得更加有趣更加丰富多彩

西瓜 2009-05-22 16:19 发表评论