在EJB中测试JTA

1、首先在jboss 中mysql-ds.xml的配置文件中配置二个数据源

<local-tx-datasource>
    <jndi-name>MySqlDS</jndi-name>
    <connection-url>jdbc:mysql://localhost:3306/ejb</connection-url>
    <driver-class>com.mysql.jdbc.Driver</driver-class>
    <user-name>root</user-name>
    <password>admin</password>
    <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name>
        <metadata>
       <type-mapping>mySQL</type-mapping>
    </metadata>
  </local-tx-datasource>
  <local-tx-datasource>
    <jndi-name>MySqlDS2</jndi-name>
    <connection-url>jdbc:mysql://localhost:3306/ejb2</connection-url>
    <driver-class>com.mysql.jdbc.Driver</driver-class>
    <user-name>root</user-name>
    <password>admin</password>
    <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name>
          <metadata>
       <type-mapping>mySQL</type-mapping>
    </metadata>
  </local-tx-datasource>

2、在建立好的ejb项目中的persistence.xml配置文件中做好相应的配置

<persistence-unit name="test" transaction-type="JTA">
  		<jta-data-source>java:/MySqlDS</jta-data-source>
  		<class>com.bjsxt.jpa.Person</class>
  		<exclude-unlisted-classes>true</exclude-unlisted-classes>
  		<properties>
  			<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
  			<property name="hibernate.show_sql" value="true"/>
  			<property name="hibernate.hbm2ddl.auto" value="update"/>
  		</properties>
	</persistence-unit>

	<persistence-unit name="test2" transaction-type="JTA">
  		<jta-data-source>java:/MySqlDS2</jta-data-source>
  		<class>com.bjsxt.jpa.User</class>
  		<exclude-unlisted-classes>true</exclude-unlisted-classes>
  		<properties>
  			<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
  			<property name="hibernate.show_sql" value="true"/>
  			<property name="hibernate.hbm2ddl.auto" value="update"/>
  		</properties>
	</persistence-unit>

3、具体编码

//为了测试不同的事物，下面编写了2个实体类
import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Person implements Serializable{
	@Id
	@GeneratedValue
	private int id;

	private String name;

	public int getId() {
		return id;
	}

	public String getName() {
		return name;
	}

	public void setId(int id) {
		this.id = id;
	}

	public void setName(String name) {
		this.name = name;
	}
}
import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class User implements Serializable{
	@Id
	@GeneratedValue
	private int id;
	private String name;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

//编写接口
public interface PersonService {	
	public void add(Person p, User u);
}

//编写实现
import javax.ejb.Local;
import javax.ejb.Remote;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
@Remote
@Local
public class PersonServiceImpl implements PersonService {
        //注意：下面的add方法中存储的二个对象是放在两个不同的数据库中的
	@PersistenceContext(unitName="test")
	private EntityManager entityManager;
	@PersistenceContext(unitName="test2")
	private EntityManager entityManager2;
	public void add(Person p, User u) {
		entityManager.persist(p);
		entityManager2.persist(u);
         //在此抛出一个异常，看事物能否回滚、
		throw new RuntimeException("Error");	}
}

//客户端调用
import javax.naming.InitialContext;

import com.bjsxt.jpa.Person;
import com.bjsxt.jpa.PersonService;
import com.bjsxt.jpa.User;

public class Client {
	public static void main(String[] args) throws Exception{
		InitialContext ctx = new InitialContext();
		PersonService ps = (PersonService)ctx.lookup("PersonServiceImpl/remote");

		Person p = new Person();
		p.setName("张三");

		User u = new User();
		u.setName("李四");

		ps.add(p, u);
   }
}

实验结果：在add方法中如果不抛出异常，那么二个数据库中的数据都能添加成功，而如果在在二个方法中有一个出现错误，事物便会回滚保证事物的一致性。