手写spring事务（注解版本）

1.首先自定义一个事务注解（类似于@Transactional）

package com.itmayiedu.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
//事务注解 设置传播行为
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ExtTransaction {	
}

3.编写切面类AopExtTransaction.java

package com.itmayiedu.aop;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.interceptor.TransactionAspectSupport;
import com.itmayiedu.annotation.ExtTransaction;
import com.itmayiedu.transaction.TransactionUtils;
@Component
@Aspect//自定义事务注解具体实现
public class AopExtTransaction {
      @Autowired// 一个事务实例  针对一个事务,所以要在TransactionUtils上加Scope(value="prototype")
      private TransactionUtils transactionUtils;
      
      @AfterThrowing("execution(* com.itmayiedu.service.*.*.*(..))")
 public void afterThrowing(){
    	// 获取当前事务进行回滚
   TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();  	  
      }
      
      @Around("execution(* com.itmayiedu.service.*.*.*(..))")
      public void around(ProceedingJoinPoint pjp) throws Throwable{
    	// 1.获取该方法上是否加上注解
    	  ExtTransaction extTransaction = getMethodExtTransaction(pjp);
    	  TransactionStatus transactionStatus = begin(extTransaction);
    	// 2.调用目标代理对象方法
    	  pjp.proceed();
    	  commit(transactionStatus);
      }

	private void commit(TransactionStatus transactionStatus) {
		// 5.如果存在注解,提交事务
		   if(transactionStatus!=null){
			   transactionUtils.commit(transactionStatus);
		   }
	}

	private TransactionStatus begin(ExtTransaction extTransaction) {
            if(extTransaction==null){
            	return null;
            }
         // 2.如果存在事务注解,开启事务
            return transactionUtils.begin();
		
	}
	
	// 获取方法上是否存在事务注解
	private ExtTransaction getMethodExtTransaction(ProceedingJoinPoint pjp) throws NoSuchMethodException, SecurityException {
		String methodName = pjp.getSignature().getName();
		// 获取目标对象
		Class<?> classTarget = pjp.getTarget().getClass();
       // 获取目标对象类型
	     Class<?>[] par = ((MethodSignature) pjp.getSignature()).getParameterTypes();
		// 获取目标对象方法
		Method objMethod = classTarget.getMethod(methodName, par);
                    Annotation[] declaredAnnotations = objMethod.getDeclaredAnnotations();
                 ExtTransaction extTransaction=(ExtTransaction) declaredAnnotations[0];
                 return extTransaction;
	}

}

3.UserServiceImpl.java

package com.itmayiedu.service.impl;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.interceptor.TransactionAspectSupport;

import com.itmayiedu.annotation.ExtTransaction;
import com.itmayiedu.dao.UserDao;
import com.itmayiedu.service.UserService;
import com.itmayiedu.transaction.TransactionUtils;
@Service
public class UserServiceImpl  implements UserService{
	@Autowired
	private UserDao userDao;
	@Autowired
	private TransactionUtils transactionUtils;
	
	@ExtTransaction
		public void add() {
			// 调用接口的时候 接口失败 需要回滚，但是日志记录不需要回滚。
			//logService.addLog(); // 后面程序发生错误，不能影响到我的回滚### 正常当addLog方法执行完毕，就应该提交事务
			userDao.add("test001", 20);
			 int i = 1 / 0;
			System.out.println("################");
			userDao.add("test002", 21);
		}
}

4.编写测试类Test01.java

package com.itmayiedu.service;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test01 {
public static void main(String[] args) {
	ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");
	UserService userService = (UserService) applicationContext.getBean("userServiceImpl");
	userService.add();
}
}

解析：在走useService.add（）之前被aop拦截，先走环绕通知（开启事务，提交事务），如果useService.add（）里面有异常就走异常通知（回滚事务）