C3P0 Configurations! Where and How?

问题

We are implementing a Web App using JPA2.0 and Hibernate3.0. Connection pool configurations are set in persistence.xml located in META-INF folder.

---

persistence.xml:

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
    <persistence-unit name="MyPU" transaction-type="RESOURCE_LOCAL">
        <!-- Entity Classes-->
        <properties>
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="bytecode.provider"   value="org.hibernate.bytecode.javassist.BytecodeProviderImpl"/>
            <property name="hibernate.connection.username" value="{username}"/>
            <property name="hibernate.connection.password" value="{password}"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.connection.url" value="{jdbc url}"/>

            <property name="hibernate.c3p0.min_size" value="1"/>
            <property name="hibernate.c3p0.timeout" value="1000"/>
            <property name="hibernate.c3p0.acquire_increment" value="1"/>
            <property name="hibernate.c3p0.idle_test_periods" value="600"/>
            <property name="hibernate.c3p0.testConnectionOnCheckin" value="true"/>
            <property name="hibernate.c3p0.preferredTestQuery" value="SELECT 1;"/>
       </properties>
    </persistence-unit>
</persistence>

---

We have a problem with connection pool configurations. It seems the configurations have no effect and the connection will be broken after 8 hours. Do we need another configuration file like hibernate.cfg.xml or hibernate.properties?

回答1:

I had this same problem with the proprieties that I put in persistence.xml didn't affect c3p0.

Looking into http://www.mchange.com/projects/c3p0/index.html#configuration_files I tried to put an xml file named c3p0-config.xml and put it in WEB-INF/classes and it work perfectly.

Here is an example of a c3p0-config.xml file:

<c3p0-config>
  <default-config>
    <property name="automaticTestTable">con_test</property>
    <property name="checkoutTimeout">30000</property>
    <property name="idleConnectionTestPeriod">30</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>

    <user-overrides user="test-user">
      <property name="maxPoolSize">10</property>
      <property name="minPoolSize">1</property>
      <property name="maxStatements">0</property>
    </user-overrides>

  </default-config>
</c3p0-config>

回答2:

Good question, bad title. :) I think I answered this question on your re-post: Best configuration of c3p0

回答3:

I had the same exact issue, my problem was that my web application container (Tomcat) was managing my database connections. I had to move the c3p0 configuration from my persistence.xml file to Tomcat's context.xml. The link Domenic D provided is a great place to start if that's your problem.

回答4:

There is a typo in your settings, it should be idle_test_period not idle_test_periods.

See this post for information about the setting: The use of c3p0.idle_test_period.

来源：https://stackoverflow.com/questions/12446266/c3p0-configurations-where-and-how