Il pool di connessioni C3p0 per jpa in persistence.xml non funziona?

Question

Sto ancora ottenendo timeout JDBC dopo aver tentato di configurare c3p0 seguendo tutti gli esempi che ho trovato. Sto usando JPA, Hibernate, Tomcat, MySQL [AWS RDS]. Ecco il frammento dal 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" /> 

E il log degli errori:

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 configurazione sembra OK. Attiva la registrazione e assicurati che C3P0 inizi con le impostazioni appropriate.

 
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

ho trovato la risposta da questo blog: http://blog.hpxn.net/2009/02/05/using-c3p0-and-hibernate-3/

Immobili a persistence.xml erano solo sbagliato, si dovrebbe incantesimo li che inizia da 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> 

E poi, si vedi questo favoloso registro visualizzato:

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  .... 

Cordiali saluti, Stéphane (mi dispiace per la taglia)