EJB之JPA(跨越多个MYSQL数据库,)

这个与配置文件有关,在JBOSS5中.需要更新下面配置文件

在JBOSS5+JDK6的环境下，要跨越多个mysql的数据库，需要使用xa-datasource（能支持两阶段提交协议的数据源）
为了使用xa-datasource，请下载最新的mysql驱动（目前是：5.1.13），因此为了测试本项目，请按以下步骤操作：

1、首先替换原来的mysql驱动为新的5.1.13

2、在JBOSS的deploy目录下，增加一个mysql-xa-ds.xml文件，文件的模板如下，请自行修改其中的JNDI名称和用户名、密码、数据库等
-------------------

<?xml version="1.0" encoding="UTF-8"?>

<!-- See http://www.jboss.org/community/wiki/Multiple1PC for information about local-tx-datasource -->
<!-- $Id: mysql-ds.xml 88948 2009-05-15 14:09:08Z jesper.pedersen $ -->
<!--  Datasource config for MySQL using 3.0.9 available from:
http://www.mysql.com/downloads/api-jdbc-stable.html
-->

<datasources>
    <xa-datasource>
         <jndi-name>MySqlDS1</jndi-name>
         <xa-datasource-property name="URL">jdbc:mysql://localhost:3306/ejb31</xa-datasource-property>
         <xa-datasource-class>com.mysql.jdbc.jdbc2.optional.MysqlXADataSource</xa-datasource-class>
         <user-name>root</user-name>
         <password>root</password>
         <track-connection-by-tx>true</track-connection-by-tx>
         <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name>
         <valid-connection-checker-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLValidConnectionChecker</valid-connection-checker-class-name>
         <min-pool-size>1</min-pool-size>
         <max-pool-size>10</max-pool-size>
         <idle-timeout-minutes>10</idle-timeout-minutes>
         <metadata>
             <type-mapping>mySQL</type-mapping>
         </metadata>
     </xa-datasource>
     <xa-datasource>
         <jndi-name>MySqlDS2</jndi-name>
         <xa-datasource-property name="URL">jdbc:mysql://localhost:3306/ejb32</xa-datasource-property>
         <xa-datasource-class>com.mysql.jdbc.jdbc2.optional.MysqlXADataSource</xa-datasource-class>
         <user-name>root</user-name>
         <password>leadfar</password>
         <track-connection-by-tx>true</track-connection-by-tx>
         <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name>
         <valid-connection-checker-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLValidConnectionChecker</valid-connection-checker-class-name>
         <min-pool-size>1</min-pool-size>
         <max-pool-size>10</max-pool-size>
         <idle-timeout-minutes>10</idle-timeout-minutes>
         <metadata>
             <type-mapping>mySQL</type-mapping>
         </metadata>
     </xa-datasource>
</datasources>

package cn.com.leadfar.jpa;

import javax.ejb.Remote;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless(name="userManager")
@Remote
public class UserManagerImpl implements UserManager {

    /**
     * 如果只定义了一个Persistence Unit，则无需指定unitName，但一旦定义了
     * 多个，则必须指定unitName
     */
    @PersistenceContext(unitName="test")
    private EntityManager em;
    
    @PersistenceContext(unitName="test2")
    private EntityManager em2;
    
    public void addUser() {
        User user = new User();
        user.setName("张三");
        em.persist(user);
        
        Person person = new Person();
        person.setName("Test Person");
        em2.persist(person);
        
        //如果抛出异常，将会导致整个事务回滚！这就是跨越数据库的事务管理
        //throw new RuntimeException("异常");
    }

}