persistence.xml中jpa的C3p0连接池不工作？ [英] C3p0 connection pooling for jpa in persistence.xml not working?

问题描述

在尝试配置c3p0之后，我仍然收到了JDBC超时，我可以找到所有示例。我正在使用JPA，Hibernate，Tomcat，MySQL [AWS RDS]。以下是persistence.xml的片段：

 < property name =javax.persistence.jdbc.url
 value =jdbc：mysql：// url .../> 
< property name =javax.persistence.jdbc.drivervalue =com.mysql.jdbc.Driver/> 
< property name =hibernate.dialectvalue =org.hibernate.dialect.MySQLDialect/> 
< property name =connection.provider_classvalue =org.hibernate.connection.C3P0ConnectionProvider/> 
< property name =hibernate.c3p0.acquire_incrementvalue =4/> 
< property name =hibernate.c3p0.idle_test_periodvalue =3000/> 
< property name =hibernate.c3p0.max_sizevalue =100/> 
< property name =hibernate.c3p0.max_statementsvalue =15/> 
< property name =hibernate.c3p0.min_sizevalue =5/> 
< property name =hibernate.c3p0.timeoutvalue =100/> 
  

以及错误日志：

  09：18：51.776 WARN org.hibernate.util.JDBCExceptionReporter  -  SQL错误：0，SQLState：08S01 
 09：18：51.777错误org.hibernate.util.JDBCExceptionReporter  - 最后从服务器成功收到的数据包是38,491,585毫秒前。 ... 
  

解决方案

我从这个博客找到答案：
http://blog.hpxn.net/2009/02 / 05 / using-c3p0-and-hibernate-3 /

persistence.xml中的属性错了，你应该用hibernate开始拼写它们：

 < persistence xmlns =http://java.sun.com/xml/ns/persistence
 xmlns ：xsi =http://www.w3.org/2001/XMLSchema-instance
 xsi：schemaLocation =http://java.sun.com/xml/ns/persistence http：// java。 sun.com/xml/ns/persistence/persistence_1_0.xsd
 version =1.0> 
< persistence-unit name =mypersistenceunitname> 
<属性> 
< property name =hibernate.connection.driver_classvalue =com.mysql.jdbc.Driver/> 
< property name =hibernate.dialectvalue =org.hibernate.dialect.MySQLDialect/> 
< property name =hibernate.hbm2ddl.autovalue =create-drop/> 
 
 <！ - 重要 - > 
< property name =hibernate.connection.provider_class
 value =org.hibernate.connection.C3P0ConnectionProvider/> 
 
< property name =hibernate.c3p0.max_sizevalue =100/> 
< property name =hibernate.c3p0.min_sizevalue =0/> 
< property name =hibernate.c3p0.acquire_incrementvalue =1/> 
< property name =hibernate.c3p0.idle_test_periodvalue =300/> 
< property name =hibernate.c3p0.max_statementsvalue =0/> 
< property name =hibernate.c3p0.timeoutvalue =100/> 
< / properties> 
< / persistence-unit> 
< /余辉> 
  

然后，您会看到这个美妙的日志出现：

  2011-08-15 08:58:33 com.mchange.v2.c3p0.C3P0Registry banner 
 INFO：Initializing c3p0-0.9.1 [built 16- January-2007 14:46:42;调试？真正; trace：10] 
 2011-08-15 08:58:33 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager 
 INFO：初始化c3p0池... com.mchange.v2.c3p0。 PoolBackedDataSource @ f3a94e12 [connectionPoolDataSource  - > 
  

Stéphane（对于赏金感到抱歉）

I'm still getting JDBC timeouts after trying to configure c3p0 following all of the examples I could find. I'm using JPA, Hibernate, Tomcat, MySQL [AWS RDS]. Here's the snippet from persistence.xml:

<property name="javax.persistence.jdbc.url"
value="jdbc:mysql://url..." />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
<property name="connection.provider_class"  value="org.hibernate.connection.C3P0ConnectionProvider"/>
<property name="hibernate.c3p0.acquire_increment" value="4" />
<property name="hibernate.c3p0.idle_test_period" value="3000" /> 
<property name="hibernate.c3p0.max_size" value="100" />
<property name="hibernate.c3p0.max_statements" value="15" />
<property name="hibernate.c3p0.min_size" value="5" />
<property name="hibernate.c3p0.timeout" value="100" /> 

And the error log:

09:18:51.776  WARN   org.hibernate.util.JDBCExceptionReporter  - SQL Error: 0, SQLState: 08S01
09:18:51.777  ERROR  org.hibernate.util.JDBCExceptionReporter  - The last packet successfully received from the server was 38,491,585 milliseconds ago.  ...

解决方案

I found the answer from this blog : http://blog.hpxn.net/2009/02/05/using-c3p0-and-hibernate-3/

Properties in persistence.xml were just wrong, you should spell them beginning by hibernate :

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence         http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
  version="1.0">
    <persistence-unit name="mypersistenceunitname">
      <properties>
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
        <property name="hibernate.hbm2ddl.auto" value="create-drop" />

        <!-- Important -->
        <property name="hibernate.connection.provider_class"
          value="org.hibernate.connection.C3P0ConnectionProvider" />

        <property name="hibernate.c3p0.max_size" value="100" />
        <property name="hibernate.c3p0.min_size" value="0" />
        <property name="hibernate.c3p0.acquire_increment" value="1" />
        <property name="hibernate.c3p0.idle_test_period" value="300" />
        <property name="hibernate.c3p0.max_statements" value="0" />
        <property name="hibernate.c3p0.timeout" value="100" />
      </properties>
    </persistence-unit>
</persistence>

And then, you will see this fabulous log appear :

2011-08-15 08:58:33 com.mchange.v2.c3p0.C3P0Registry banner
INFO: Initializing c3p0-0.9.1 [built 16-January-2007 14:46:42; debug? true; trace: 10]
2011-08-15 08:58:33 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
INFO: Initializing c3p0 pool... com.mchange.v2.c3p0.PoolBackedDataSource@f3a94e12 [     connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@6297f706     ....

Regards, Stéphane (sorry for the bounty)

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