How to configure Java Spring's annotation-based AOP

1 Environment setup

1.1 Step 1: Prepare necessary code and jar package

• Copy A short project is enough.

1.2 Step 2: Import the context namespace in the configuration file

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
 
    <!-- 配置数据库操作对象 -->
    <bean id="dbAssit" class="com.itheima.dbassit.DBAssit">
        <property name="dataSource" ref="dataSource"></property>
        
        <!-- 指定 connection 和线程绑定 -->
        <property name="useCurrentConnection" value="true"></property>
    </bean>
 
    <!-- 配置数据源 -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="com.mysql.jdbc.Driver"></property>
        <property name="jdbcUrl" value="jdbc:mysql:///spring_day02"></property>
        <property name="user" value="root"></property>
        <property name="password" value="1234"></property>
    </bean>
</beans>

1.3 Step 3: Configure resource usage annotations

• Account’s business layer implementation class

@Service("accountService")
public class AccountServiceImpl implements IAccountService {
 
    @Autowired
    private IAccountDao accountDao;
}

• Account’s persistence layer implementation class

@Repository("accountDao")
public class AccountDaoImpl implements IAccountDao {
    @Autowired
    private DBAssit dbAssit ;
}

1.4 Step 4: Specify the packages to be scanned by spring in the configuration file

<!-- 告知 spring，在创建容器时要扫描的包 -->
<context:component-scan base-package="com.itheima"></context:component-scan>

2 Configuration steps

2.1 Step 1: Configure the notification class using annotations

• Transaction Control Class

@Component("txManager")
public class TransactionManager {
 
    //定义一个 DBAssit
    @Autowired
    private DBAssit dbAssit ;
}

2.2 Step 2: Use the @Aspect annotation on the notification class to declare it as an aspect

• Function:

• Declare the current class as an aspect class.

• Transaction control class

@Component("txManager")
@Aspect//表明当前类是一个切面类
public class TransactionManager {
 
    //定义一个 DBAssit
    @Autowired
    private DBAssit dbAssit ;
}

2.3 Step 3: Use annotations to configure notifications on the enhanced method

2.3.1 @Before

• Function:

• Treat the current method as a pre-notification.

• Attributes:

• value: used to specify the entry point expression, you can also specify the entry point expression Quote.

//开启事务
@Before("execution(* com.itheima.service.impl.*.*(..))")
public void beginTransaction() {
 
    try {
        dbAssit.getCurrentConnection().setAutoCommit(false);
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

2.3.2 @AfterReturning

• Function:

• Think of the current method as a post-advice.

• Attributes:

• value: used to specify the entry point expression, you can also specify the entry point expression Quote

//提交事务
@AfterReturning("execution(* com.itheima.service.impl.*.*(..))")
public void commit() {
 
    try {
        dbAssit.getCurrentConnection().commit();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

2.3.3 @AfterThrowing

• Function:

• Consider the current method as an exception notification.

• Attributes:

• value: used to specify the entry point expression, you can also specify the entry point expression Quote

//回滚事务
@AfterThrowing("execution(* com.itheima.service.impl.*.*(..))")
public void rollback() {
 
    try {
        dbAssit.getCurrentConnection().rollback();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

2.3.4 @After

• Function:

• Consider the current method as the final notification.

• Attributes:

• value: used to specify the entry point expression, you can also specify the entry point expression Quote

//释放资源
@After("execution(* com.itheima.service.impl.*.*(..))")
public void release() {
 
    try {
        dbAssit.releaseConnection();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

2.4 Step 4: Enable spring’s support for annotation AOP in the spring configuration file

<!-- 开启 spring 对注解 AOP 的支持 -->
<aop:aspectj-autoproxy/>

3 Surround notification annotation configuration @Around

• Function:

• Treat the current method as a surrounding notification.

• Attributes:

• value: used to specify the entry point expression, you can also specify the entry point expression Quote.

/**
* 环绕通知
* @param pjp
* @return
*/
@Around("execution(* com.itheima.service.impl.*.*(..))")
public Object transactionAround(ProceedingJoinPoint pjp) {
 
    //定义返回值
    Object rtValue = null;
 
    try {
    
        //获取方法执行所需的参数
        Object[] args = pjp.getArgs();
    
        //前置通知：开启事务
        beginTransaction();
 
        //执行方法
        rtValue = pjp.proceed(args);
 
        //后置通知：提交事务
        commit();
        }catch(Throwable e) {
 
        //异常通知：回滚事务
        rollback();
        e.printStackTrace();
    }finally {
 
    //最终通知：释放资源
    release();
    }
 
    return rtValue;
}

4 Pointcut expression annotation @Pointcut

• Function:

• Specify the entry point expression

• Attributes:

• value: The content of the specified expression

@Pointcut("execution(* com.itheima.service.impl.*.*(..))")
private void pt1() {}
 
    /**
    * 引用方式：
    * 环绕通知
    * @param pjp
    * @return
    */
    @Around("pt1()")//注意：千万别忘了写括号
    public Object transactionAround(ProceedingJoinPoint pjp) {
 
    //定义返回值
    Object rtValue = null;
 
    try {
        //获取方法执行所需的参数
        Object[] args = pjp.getArgs();
 
        //前置通知：开启事务
        beginTransaction();
        
        //执行方法
        rtValue = pjp.proceed(args);
 
        //后置通知：提交事务
        commit();
    }catch(Throwable e) {
 
        //异常通知：回滚事务
        rollback();
        e.printStackTrace();
    }finally {
 
        //最终通知：释放资源
        release();
    }
    
    return rtValue;
}

5 Configuration method without XML

@Configuration
@ComponentScan(basePackages="com.itheima")
@EnableAspectJAutoProxy
public class SpringConfiguration {
 
}

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