今天試著在Hibernate中Config Connection Pool時發現 Hibernate3.3.1 GA版裡面，已經將C3P0ConnectionProvider這個class搬到 hibernate-c3p0-3.3.1.GA.jar這個Jar中了，可以到這個網址下載http://www.java2s.com/Code/Jar/GHI/Downloadhibernatec3p0331GAjar.htm
把它加到build path後，編輯persistence.xml。Mark紅色的部分，即為新增的Connection Pool設定。
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" 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">
<persistence-unit name="Test">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.connection.driver_class" value="com.ibm.db2.jcc.DB2Driver"/>
<property name="hibernate.connection.password" value="db2admin"/>
<property name="hibernate.connection.url" value="jdbc:db2://localhost:50000/puli"/>
<property name="hibernate.connection.username" value="db2admin"/>
<property name="hibernate.default_schema" value="db2admin"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.DB2Dialect"/>
<!--使用c3p Connection Pool -->
<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="3" />
<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>
回到使用JPA的程式碼，假設在以下的程式碼中，在把程式由原本的standalone轉成使用connection pool後，不能在程式碼裡面呼叫JPAUtil.shutdown()這個方法，因為這個方法會把connection中斷。
public class PuliTest {
public static void main(String[] args) {
EntityManager newEntityManager =
JPAUtil.getEntityManagerFactory().createEntityManager();
EntityTransaction newEtx = newEntityManager.getTransaction();
newEtx.begin();
PatientBasicInfo patient = (PatientBasicInfo) newEntityManager.find(PatientBasicInfo.class, "12345");
System.out.println(patient.getPatientfirstname());
System.out.println(patient.getPatientlastname());
System.out.println(patient.getPatientaddress());
newEtx.commit();
newEntityManager.close();
//JPAUtil.shutdown(); 在使用connection pool的程式中，需 comment掉此method call
}
}
