0


Spring AOP 学习(动态代理、JdbcTemplate、Junit)

动态代理

Proxy jdk动态代理,面向接口

cglib 第三方动态代理,面向父类

jdk动态代理

public class Test1 {
    public static void main(String[] args) {
        Dinner dinner=new Person("张三");
        // 通过Porxy动态代理获得一个代理对象,在代理对象中,对某个方法进行增强
//        ClassLoader loader,被代理的对象的类加载器
        ClassLoader classLoader = dinner.getClass().getClassLoader();
//        Class<?>[] interfaces,被代理对象所实现的所有接口
        Class[] interaces= dinner.getClass().getInterfaces();
//        InvocationHandler h,执行处理器对象,专门用于定义增强的规则
        InvocationHandler handler = new InvocationHandler(){
            // invoke 当我们让代理对象调用任何方法时,都会触发invoke方法的执行
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
//                Object proxy, 代理对象
//                Method method,被代理的方法
//                Object[] args,被代理方法运行时的实参
                Object res=null;
               if(method.getName().equals("eat")){
                   System.out.println("饭前洗手");
                   // 让原有的eat的方法去运行
                   res =method.invoke(dinner, args);
                   System.out.println("饭后刷碗");
               }else{
                   // 如果是其他方法,那么正常执行就可以了
                   res =method.invoke(dinner, args);
               }
                return res;
            }
        };
        Dinner dinnerProxy =(Dinner) Proxy.newProxyInstance(classLoader,interaces,handler);
        //dinnerProxy.eat("包子");
        dinnerProxy.drink();
    }
}
interface Dinner{
    void eat(String foodName);
    void drink();
}
class Person implements Dinner{
    private String name;
    public Person(String name) {
        this.name = name;
    }
    @Override
    public void eat(String foodName) {
        System.out.println(name+"正在吃"+foodName);
    }
    @Override
    public void drink( ) {
        System.out.println(name+"正在喝茶");
    }
}
class Student implements Dinner{
    private String name;
    public Student(String name) {
        this.name = name;
    }
    @Override
    public void eat(String foodName) {
        System.out.println(name+"正在食堂吃"+foodName);
    }
    @Override
    public void drink( ) {
        System.out.println(name+"正在喝可乐");
    }
}

不修改原有代码,或者没有办法修改原有代码的情况下,增强对象功能,使用代理对象代替原来的对象去完成功能,进而达到拓展功能的目的

JDK Proxy 动态代理是面向接口的动态代理,一定要有接口和实现类的存在,代理对象增强的是实现类实现接口时重写的方法

生成的代理对象只能转换成接口,不能转换成被代理类(上面只能是Dinner,不能是Person或Student)

代理对象只能增强接口中定义的方法, 实现类中其他和接口无关的方法是无法增强的

代理对象只能读取到接口中方法上的注解,不能读取到实现类方法上的注解

cglib动态代理

面向父类的,和接口没有直接关系

不仅仅可以增强接口中定义的方法,还可以增强一个类的其他方法

可以读取父类中方法上的所有注解

public class Test1 {
    @Test
    public void testCglib(){
        Person person =new Person();
        // 1 获得一个Enhancer对象
        Enhancer enhancer=new Enhancer();
        // 2 设置父类字节码
        enhancer.setSuperclass(person.getClass());
        // 3 获取MethodIntercepter对象 用于定义增强规则
        MethodInterceptor methodInterceptor=new MethodInterceptor() {
            @Override
            public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                /*Object o,  生成之后的代理对象 personProxy
                Method method,  父类中原本要执行的方法  Person>>> eat()
                Object[] objects, 方法在调用时传入的实参数组
                MethodProxy methodProxy  子类中重写父类的方法 personProxy >>> eat()
                */
                Object res =null;
                if(method.getName().equals("eat")){
                    // 如果是eat方法 则增强并运行
                    System.out.println("饭前洗手");
                    res=methodProxy.invokeSuper(o,objects);
                    System.out.println("饭后刷碗");
                }else{
                    // 如果是其他方法 不增强运行
                    res=methodProxy.invokeSuper(o,objects); // 子类对象方法在执行,默认会调用父类对应被重写的方法
                }
                return res;
            }
        };
        // 4 设置methodInterceptor
        enhancer.setCallback(methodInterceptor);
        // 5 获得代理对象
        Person personProxy = (Person)enhancer.create();
        // 6 使用代理对象完成功能
        personProxy.eat("包子");
    }
}
class Person  {
    public Person( ) {
    }
    public void eat(String foodName) {
        System.out.println("张三正在吃"+foodName);
    }
}

AOP概念

AOP切面编程一般可以帮助我们在不修改现有代码的情况下,对程序的功能进行拓展,往往用于实现日志处理,权限控制,性能检测,事务控制

AOP实现的原理就是动态代理

在有接口的情况下,使用JDK动态代理,在没有接口的情况下使用cglib动态代理

开闭原则:对于扩展是开放的,但是对于修改是封闭的

连接点 Joint point

类里面那些可以被增强的方法,这些方法称之为连接点(可以被增强,不一定真的被增强了)

切入点 Pointcut

实际被增强的方法,称之为切入点

通知 Advice

实际增强的逻辑部分称为通知 (增加的功能)

通知类型: 1 前置通知 2 后置通知 3 环绕通知 4 异常通知 5 最终通知

目标对象 Target

被增强功能的对象(被代理的对象)

织入 Advice 的目标对象

切面Aspect

表现为功能相关的一些advice方法放在一起声明成的一个Java类

织入 Weaving

创建代理对象并实现功能增强的声明并运行过程

切入点表达式

execution([权限修饰符][返回值类型][类的全路径名][方法名](参数 列表) )

execution(* com.msb.dao.UserDaoImpl.add(..)) //指定切点为UserDaoImpl.add方法

execution(* com.msb.dao.UserDaoImpl.*(..)) //指定切点为UserDaoImpl.所有的方法

execution(* com.msb.dao..(..)) //指定切点为dao包下所有的类中的所有的方法

execution(* com.msb.dao.*.add(..)) // 指定切点为dao包下所有的类中的add的方法

execution(* com.msb.dao..add(..)) // 指定切点为dao包下所有的类中的add开头的方法

通知类型

前置通知@Before

切点方法执行之前先执行的功能,参数列表可以用JoinPoint接收切点对象

后置通知@After

方法执行之后要增强的功能,无论切点方法是否出现异常都会执行的方法(最终通知)

返回通知@AfterReturning

切点方法正常运行结束后增强的功能,

    @AfterReturning( value = "execution(* com.msb.dao.UserDaoImpl.add(..))",returning = "res")
    public void methodAfterReturning(JoinPoint joinPoint,Object res){
        System.out.println("AfterReturning invoked");
    }

如果方法运行过程中出现异常,则该功能不运行

参数列表可以用 JoinPoint joinPoint接收切点对象
可以用Object res接收方法返回值,需要用returning指定返回值名称

异常通知 @AfterThrowing

切点方法出现异常时运行的增强功能,如果方法运行没有出现异常,则该功能不运行

参数列表可以用Exception ex接收异常对象 需要通过throwing指定异常名称

    @AfterThrowing( value = "execution(* com.msb.dao.UserDaoImpl.add(..))",throwing = "ex")
    public void methodAfterThrowing(Exception ex){
        System.out.println("AfterThrowing invoked");
    }

环绕通知@Around

在切点方法之前和之后都进行功能的增强

需要在通知中定义方法执行的位置,并在执行位置之前和之后自定义增强的功能

方法列表可以通过ProceedingJoinPoint获取执行的切点

通过proceedingJoinPoint.proceed()方法控制切点方法的执行位置

proceedingJoinPoint.proceed()方法会将切点方法的返回值获取到,可以用来做后续处理

我们在环绕通知的最后需要将切点方法的返回值继续向上返回,否则切点方法在执行时接收不到返回值


    @Around("execution(* com.msb.dao.UserDaoImpl.add(..))")
    public Object methodAround(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
        System.out.println("aroundA invoked");
        Object proceed = proceedingJoinPoint.proceed();
        System.out.println("aroundB invoked");
        return proceed;
    }

公共切点

定义

    @Pointcut("execution(* com.msb.dao.*.add*(..))")
    public void addPointCut(){}

使用

@Before("addPointCut()")

通知顺序:@Around before =》@Before =》方法调用=》@AfterReturning/@AfterThrowing=》@After=》@Around after

@Order

可以指定代理顺序,数字越小,越靠后被代理,也就是@Around before越先执行

@EnableAspectJAutoProxy(proxyTargetClass=true)

开启自动代理

使用aop需要开启包扫描和开启自动代理

JdbcTemplate

可以使用JdbcTemplate实现查询

// 查询个数
Integer empCount = jdbcTemplate.queryForObject("select count(1) from emp", Integer.class);
// 查询单个对象
BeanPropertyRowMapper<Emp> rowMapper =new BeanPropertyRowMapper<>(Emp.class);
Emp emp = jdbcTemplate.queryForObject("select * from emp where empno =?", rowMapper, empno);
        

插入

        // 批量新增操作
        String sql ="insert into dept values(DEFAULT,?,?)";
        List<Object[]> args =new LinkedList<>();
        for (Dept dept : depts) {
            Object[] arg ={dept.getDname(),dept.getLoc()};
            args.add(arg);
        }
        return jdbcTemplate.batchUpdate(sql, args);

查看接口实现类

ctrl + h

事务

@Transactional注解放在类上,表示该类中所有方法都加事务

加了@Transactional注解后,该方法中两个dao操作会保持原子性

@Transactional的参数

public @interface Transactional {

    /**
     * Alias for {@link #transactionManager}.
     * @see #transactionManager
     */
    @AliasFor("transactionManager")
    String value() default "";

    /**
     * A <em>qualifier</em> value for the specified transaction.
     * <p>May be used to determine the target transaction manager, matching the
     * qualifier value (or the bean name) of a specific
     * {@link org.springframework.transaction.TransactionManager TransactionManager}
     * bean definition.
     * @since 4.2
     * @see #value
     * @see org.springframework.transaction.PlatformTransactionManager
     * @see org.springframework.transaction.ReactiveTransactionManager
     */
    @AliasFor("value")
    String transactionManager() default "";

    /**
     * The transaction propagation type.
     * <p>Defaults to {@link Propagation#REQUIRED}.
     * @see org.springframework.transaction.interceptor.TransactionAttribute#getPropagationBehavior()
     */
    Propagation propagation() default Propagation.REQUIRED;

    /**
     * The transaction isolation level.
     * <p>Defaults to {@link Isolation#DEFAULT}.
     * <p>Exclusively designed for use with {@link Propagation#REQUIRED} or
     * {@link Propagation#REQUIRES_NEW} since it only applies to newly started
     * transactions. Consider switching the "validateExistingTransactions" flag to
     * "true" on your transaction manager if you'd like isolation level declarations
     * to get rejected when participating in an existing transaction with a different
     * isolation level.
     * @see org.springframework.transaction.interceptor.TransactionAttribute#getIsolationLevel()
     * @see org.springframework.transaction.support.AbstractPlatformTransactionManager#setValidateExistingTransaction
     */
    Isolation isolation() default Isolation.DEFAULT;

    /**
     * The timeout for this transaction (in seconds).
     * <p>Defaults to the default timeout of the underlying transaction system.
     * <p>Exclusively designed for use with {@link Propagation#REQUIRED} or
     * {@link Propagation#REQUIRES_NEW} since it only applies to newly started
     * transactions.
     * @see org.springframework.transaction.interceptor.TransactionAttribute#getTimeout()
     */
    int timeout() default TransactionDefinition.TIMEOUT_DEFAULT;

    /**
     * A boolean flag that can be set to {@code true} if the transaction is
     * effectively read-only, allowing for corresponding optimizations at runtime.
     * <p>Defaults to {@code false}.
     * <p>This just serves as a hint for the actual transaction subsystem;
     * it will <i>not necessarily</i> cause failure of write access attempts.
     * A transaction manager which cannot interpret the read-only hint will
     * <i>not</i> throw an exception when asked for a read-only transaction
     * but rather silently ignore the hint.
     * @see org.springframework.transaction.interceptor.TransactionAttribute#isReadOnly()
     * @see org.springframework.transaction.support.TransactionSynchronizationManager#isCurrentTransactionReadOnly()
     */
    boolean readOnly() default false;

    /**
     * Defines zero (0) or more exception {@link Class classes}, which must be
     * subclasses of {@link Throwable}, indicating which exception types must cause
     * a transaction rollback.
     * <p>By default, a transaction will be rolling back on {@link RuntimeException}
     * and {@link Error} but not on checked exceptions (business exceptions). See
     * {@link org.springframework.transaction.interceptor.DefaultTransactionAttribute#rollbackOn(Throwable)}
     * for a detailed explanation.
     * <p>This is the preferred way to construct a rollback rule (in contrast to
     * {@link #rollbackForClassName}), matching the exception class and its subclasses.
     * <p>Similar to {@link org.springframework.transaction.interceptor.RollbackRuleAttribute#RollbackRuleAttribute(Class clazz)}.
     * @see #rollbackForClassName
     * @see org.springframework.transaction.interceptor.DefaultTransactionAttribute#rollbackOn(Throwable)
     */
    Class<? extends Throwable>[] rollbackFor() default {};

    /**
     * Defines zero (0) or more exception names (for exceptions which must be a
     * subclass of {@link Throwable}), indicating which exception types must cause
     * a transaction rollback.
     * <p>This can be a substring of a fully qualified class name, with no wildcard
     * support at present. For example, a value of {@code "ServletException"} would
     * match {@code javax.servlet.ServletException} and its subclasses.
     * <p><b>NB:</b> Consider carefully how specific the pattern is and whether
     * to include package information (which isn't mandatory). For example,
     * {@code "Exception"} will match nearly anything and will probably hide other
     * rules. {@code "java.lang.Exception"} would be correct if {@code "Exception"}
     * were meant to define a rule for all checked exceptions. With more unusual
     * {@link Exception} names such as {@code "BaseBusinessException"} there is no
     * need to use a FQN.
     * <p>Similar to {@link org.springframework.transaction.interceptor.RollbackRuleAttribute#RollbackRuleAttribute(String exceptionName)}.
     * @see #rollbackFor
     * @see org.springframework.transaction.interceptor.DefaultTransactionAttribute#rollbackOn(Throwable)
     */
    String[] rollbackForClassName() default {};

    /**
     * Defines zero (0) or more exception {@link Class Classes}, which must be
     * subclasses of {@link Throwable}, indicating which exception types must
     * <b>not</b> cause a transaction rollback.
     * <p>This is the preferred way to construct a rollback rule (in contrast
     * to {@link #noRollbackForClassName}), matching the exception class and
     * its subclasses.
     * <p>Similar to {@link org.springframework.transaction.interceptor.NoRollbackRuleAttribute#NoRollbackRuleAttribute(Class clazz)}.
     * @see #noRollbackForClassName
     * @see org.springframework.transaction.interceptor.DefaultTransactionAttribute#rollbackOn(Throwable)
     */
    Class<? extends Throwable>[] noRollbackFor() default {};

    /**
     * Defines zero (0) or more exception names (for exceptions which must be a
     * subclass of {@link Throwable}) indicating which exception types must <b>not</b>
     * cause a transaction rollback.
     * <p>See the description of {@link #rollbackForClassName} for further
     * information on how the specified names are treated.
     * <p>Similar to {@link org.springframework.transaction.interceptor.NoRollbackRuleAttribute#NoRollbackRuleAttribute(String exceptionName)}.
     * @see #noRollbackFor
     * @see org.springframework.transaction.interceptor.DefaultTransactionAttribute#rollbackOn(Throwable)
     */
    String[] noRollbackForClassName() default {};

}

事务的传播行为:多事务方法之间调用,事务是如何管理的

Junit用法

spring中junit4

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:xxx.xml")
public class Test05 {
}

spring中junit5

@ExtendWith(SpringExtension.class)
@ContextConfiguration("classpath:xxx.xml")
public class Test06 {
}

相当于

@SpringJUnitConfig(locations = "xxx.xml")
public class Test06 {
}
标签: spring java

本文转载自: https://blog.csdn.net/CelineT/article/details/130966366
版权归原作者 CelineT 所有, 如有侵权,请联系我们删除。

“Spring AOP 学习(动态代理、JdbcTemplate、Junit)”的评论:

还没有评论