transactiondaobean.java

精通EJB3源码

package com.foshanshop.ejb3.impl;

import javax.annotation.Resource;
import javax.ejb.EJB;
import javax.ejb.Remote;
import javax.ejb.SessionContext;
import javax.ejb.Stateless;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import com.foshanshop.ejb3.OtherDAO;
import com.foshanshop.ejb3.AppException;
import com.foshanshop.ejb3.TransactionDAO;
import com.foshanshop.ejb3.bean.Product;

@Stateless
@Remote (TransactionDAO.class)
public class TransactionDAOBean implements TransactionDAO {
    @PersistenceContext protected EntityManager em;
    @EJB OtherDAO otherejb;
    @Resource SessionContext ejbcontext;

    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void systemException() {//抛出javax.ejb.EJBTransactionRolledbackException
    	otherejb.systemException();
    }

    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void AppException() throws AppException{
    	em.persist(new Product("巴巴运动网", (float)27));
        throw new AppException ("抛出应用例外");//会引起事务回滚
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void setRollback(){
    	em.persist(new Product("手工设置事务回滚", (float)86));
    	ejbcontext.setRollbackOnly();
    }
    
    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public void requried_notInTransaction(){
    	otherejb.required();//该方法会为自己开启事务
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void requried_inTransaction(){
    	otherejb.required();//该方法会成为当前事务的一部分
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public Product notSupported_runInTransaction(Product product){
    	em.persist(product);
    	em.flush();
    	//下面一行代码执行前，当前事务被挂起
    	Product result = otherejb.notSupported(product.getProductid());//如果事务的隔离级别为Read Committed(避免脏读)，该方法的返回结果为null，这是因为该ejb不在当前事务，而当前事务尚未提交，所以获取不到刚插入的记录
    	//上面一行代码执行结束后，原先的事务便会恢复
    	product.setName("事务恢复后的更新");
    	return result;
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void mandatory_inTransaction(){
    	otherejb.mandatory();//该方法会成为当前事务的一部分
    }
    
    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public void mandatory_notInTransaction(){
    	otherejb.mandatory();//执行到该方法会抛出EJBTransactionRequiredException例外
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void requirednew_inTransaction(){
    	Product p = new Product("巴巴运动网", (float)56);
    	em.persist(p);
    	otherejb.requirednew();//该方法会为自己开启一个新事务，原有事务被挂起，直到该方法执行结束，原有事务才会恢复执行
    	p.setName("运动用品");
    }
    
    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public void requirednew_notInTransaction(){
    	otherejb.requirednew();//该方法会为自己开启一个新事务
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public Product support_inTransaction(){
    	Product p = new Product("体育用品", (float)920);
    	em.persist(p);
    	em.flush();
    	Product result = otherejb.support(p.getProductid());//该方法会成为当前事务的一部分
    	p.setName("户外用品");
    	return result;
    }
    
    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public Product support_notInTransaction(){
    	return otherejb.support(1);//因当前没有事务，所以该方法在没有事务的环境下执行
    }
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public Product never_inTransaction(int productid){
    	return otherejb.never(productid);//因方法在事务范围内被调用，所以容器会抛出EJBException例外
    }
    
    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public Product never_notInTransaction(int productid){
    	return otherejb.never(productid);//该方法在事务范围外调用
    }
}