spring4中文技术手册==

spring4中文技术手册==spring4中文技术手册在《静态代理和动态代理》中提到了面向方面编程，主要就是基于动态代理。单独抽象出非业务的功能，服务于某些业务方法。Spring提供了四种很实用的Advice，分别为：BeforeAdvice,AfterReturningAdvice,AroundAdvice,AfterthrowingAdvice。都是方法级别的，就是在某个方法执行前后插入一些非业务的操作，如打日志或者判断权限等。对于这四种advice的实现，spring都提供了三种方法，分别为基于接口、基于xml和基于annotation(注释)。BeforeAdvice会在目标对象的方法执行之前被调用；AfterAdvice会在目标方法执行之后被调用；AroundAdvice则可以在目标方法执行前后同时加上相关服务；ThrowAdvice是在异常发生后执行某些操作。1.基于接口的Advice这个就需要自定义的Aspect实现Spring接口。BeforeAdvice需要实现org.springframework.aop.MethodBeforeAdvice接口：/**

*

Advice

invoked

before

a

method

is

invoked.

Such

advices

cannot

*

prevent

the

method

call

proceeding,

unless

they

throw

a

Throwable.

*/

public

interface

MethodBeforeAdvice

extends

BeforeAdvice

{

/**

*

Callback

before

a

given

method

is

invoked.

*

@param

method

method

being

invoked

*

@param

args

arguments

to

the

method

*

@param

target

target

of

the

method

invocation.

May

be

<code>null</code>.

*

@throws

Throwable

if

this

object

wishes

to

abort

the

call.

*

Any

exception

thrown

will

be

returned

to

the

caller

if

it's

*

allowed

by

the

method

signature.

Otherwise

the

exception

*

will

be

wrapped

as

a

runtime

exception.

*/

void

before(Method

method,

Object[]

args,

Object

target)

throws

Throwable;

}

AfterAdvice实现org.springframework.aop.AfterReturningAdvice接口：spring4中文技术手册==全文共5页，当前为第1页。/**

spring4中文技术手册==全文共5页，当前为第1页。

*

After

returning

advice

is

invoked

only

on

normal

method

return,

not

if

an

*

exception

is

thrown.

Such

advice

can

see

the

return

value,

but

cannot

change

it.

*/

public

interface

AfterReturningAdvice

extends

AfterAdvice

{

/**

*

Callback

after

a

given

method

successfully

returned.

*

@param

returnValue

the

value

returned

by

the

method,

if

any

*

@param

method

method

being

invoked

*

@param

args

arguments

to

the

method

*

@param

target

target

of

the

method

invocation.

May

be

<code>null</code>.

*

@throws

Throwable

if

this

object

wishes

to

abort

the

call.

*

Any

exception

thrown

will

be

returned

to

the

caller

if

it's

*

allowed

by

the

method

signature.

Otherwise

the

exception

*

will

be

wrapped

as

a

runtime

exception.

*/

void

afterReturning(Object

returnValue,

Method

method,

Object[]

args,

Object

target)

throws

Throwable;

}

AroundAdvice需要实现ercept.MethodInterceptor接口：/**

*

<p>The

user

should

implement

the

{@link

#invoke(MethodInvocation)}

*

method

to

modify

the

original

behavior.

E.g.

the

following

class

*

implements

a

tracing

interceptor

(traces

all

the

calls

on

the

*

intercepted

method(s)):

*

*

<pre

class=code>

*

class

TracingInterceptor

implements

MethodInterceptor

{

*

Object

invoke(MethodInvocation

i)

throws

Throwable

{

*

System.out.println("method

"+i.getMethod()+"

is

called

on

"+

*

i.getThis()+"

with

args

"+i.getArguments());

*

Object

ret=ceed();

*

System.out.println("method

"+i.getMethod()+"

returns

"+ret);

spring4中文技术手册==全文共5页，当前为第2页。

*

return

ret;

spring4中文技术手册==全文共5页，当前为第2页。

*

}

*

}

*

</pre>

*/

public

interface

MethodInterceptor

extends

Interceptor

{

/**

*

Implement

this

method

to

perform

extra

treatments

before

and

*

after

the

invocation.

Polite

implementations

would

certainly

*

like

to

invoke

{@link

Joinpoint#proceed()}.

*

*

@param

invocation

the

method

invocation

joinpoint

*

@return

the

result

of

the

call

to

{@link

*

Joinpoint#proceed()},

might

be

intercepted

by

the

*

interceptor.

*

*

@throws

Throwable

if

the

interceptors

or

the

*

target-object

throws

an

exception.

*/

Object

invoke(MethodInvocation

invocation)

throws

Throwable;

}

类前面的注释说明了该方法的使用，就是要在invoke()方法中调用MethodIceed()，将执行传给下一个Interceptor，最终执行目标方法。在proceed()方法前后加操作，到达Aroudadvice的作用。在Aspect定义好后，就需要在bean定义文件中进行配置，通过org.springframework.aop.framework.ProxyFactoryBean的配置，指出接口、目标类和Aspect。如下：<bean

id="helloProxy"

class="org.springframework.aop.framework.ProxyFactoryBean">

<!--

业务接口

-->

<property

name="proxyInterfaces"

value="spring.advice.IHello"/>

<!--

实现该接口的目标类

-->

<property

name="target"

ref="helloSpeaker"/>

<!--

要应用的解释器，即实现非业务操作的Aspect

-->

<property

name="interceptorNames">

<list>

<value>throwAdvice</value>

<!--

还可以继续加,如

spring4中文技术手册==全文共5页，当前为第3页。

<value>logBeforeAdvice</value>

-->

spring4中文技术手册==全文共5页，当前为第3页。

</list>

</property>

</bean>

补充下，其中的目标类、解释器(Aspect)都要在Bean定义文件中先进行定义，然后才可以引用的。我们使用时，代码如下：IHello

helloProxy=(IHello)context.getBean("helloProxy");

helloProxy.hello();

在Bean定义文件中配置的Aspect就会在合适的joinPoint应用到目标方法上。补：IHello接口中有hello()方法，HelloSpeaker类实现了IHello接口。以免糊涂，给个实例如下，功能是在hello()方法前后加入日志记录。public

class

AroundAdvice

implements

MethodInterceptor{

private

Logger

logger=

Logger.getLogger(this.getClass().getName());

@Override

public

Object

invoke(MethodInvocation

methodInvocation)

throws

Throwable

{

logger.log(Level.INFO,

"method

starts..."+methodInvocation.getMethod());

Object

result=methodIceed();

logger.log(Level.INFO,"method

ends..."+methodInvocation.getMethod());

return

result;

}

}

配置：<?xml

version="1.0"

encoding="UTF-8"?>

<beans

xmlns="://./schema/beans"

xmlns:xsi="://./2001/XMLSchema-instance"

xsi:schemaLocation="://./schema/beans

://./schema/beans/spring-beans-3.0.xsd">

spring4中文技术手册==全文共5页，当前为第4页。

<bean

id="helloSpeaker"

class="spring.advice.HelloSpeaker"/>

spring4中文技术手册==全文共5页，当前为第