La agrupación de conexiones C3p0 para jpa en persistence.xml no funciona?

Question

Todavía recibo tiempos de espera de JDBC después de intentar configurar c3p0 siguiendo todos los ejemplos que pude encontrar. Estoy usando JPA, Hibernate, Tomcat, MySQL [AWS RDS]. Aquí está el fragmento de 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" /> 

Y el registro de errores:

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. ... 

Answer 1

La configuración se ve bien. Active el registro y asegúrese de que C3P0 esté comenzando con la configuración adecuada.

 
2010-10-16 11:58:31,271 INFO [main] o.h.c.ConnectionProviderFactory [ConnectionProviderFactory.java:173] Initializing connection provider: org.hibernate.connection.C3P0ConnectionProvider 
... 

Answer 2

he encontrado la respuesta desde este blog: http://blog.hpxn.net/2009/02/05/using-c3p0-and-hibernate-3/

Propiedades en persistence.xml eran simplemente incorrecto, debe deletrearlas empezando por hibernación:

<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> 

Y luego, se le ver este fabuloso registro aparecerá:

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  .... 

Atentamente, Stéphane (perdón por la recompensa)