Spring Note (c): an AOP explanation

First, the principle of AOP

(a) dynamic agent

1, see: Java Advanced (vii): detailed Java Agent

2, mainly proxy and Invocationhandle R interface

(ii) CGLIB implementation

1, mainly enhancer and Methodinterceptor interface

2, the implementation code is as follows:

<span style= "FONT-SIZE:18PX;" >/** * Using Cglib to implement * @param TARGRT * @return */public static object Getcgproxy (final Object targrt,final Advice Advice) {//Take advantage of enhancerenhancer enhancer in cglib = new enhancer ();//Set the target class as the parent of the proxy (inheriting the target class, overwriting all its non-final methods) Enhancer.setsuperclass ( Targrt.getclass ());//Set callback Enhancer.setcallback (new Methodinterceptor () {//Implement Methodinterceptor interface @overridepublic Object Intercept (Object proxy, method, object[] args, Methodproxy methodproxy) throws Throwable {Object object = Nu Ll;try{advice.before (method);//Front object = Methodproxy.invoke (Targrt, args); Advice.after (method);//Post}catch ( Exception e) {Advice.afterthrow (method);//Exception}finally{advice.afterfinally (method);//Final}return object;}}); return Enhancer.create ();} </span>

(iii) Environment and Concepts

1. Required Package: Spring package, also need Aspectjweaver.jar,aopalliance.jar, Asm.jar and Cglib.jar.

2. How AOP is implemented:Spring interface, schema configuration and annotations three ways

3. Concept

1) Tangent (aspect): A class used to interpolate business methods.

2) connection point (Joinpoint): is the aspect class and the business class connection point, in fact is encapsulates the business method some basic attribute, as the notification parameter to parse.

3) Notification (advice): in the Slice class, declare a method that does additional processing for the business method.

4) entry point (pointcut): The method specified in the business class as the point at which the tangent cuts in. is to designate a method as a tangent.

5) target object: the object being proxied.

6)AOP agent (AOP proxy): proxy object.

7) pre-notification (before advice): executed before the pointcut.

8) post notification (after returning advice): executes the notification after the Pointcut execution is complete.

9) surround notification (around advice): surrounds the Pointcut, invokes the method before and after the custom behavior is completed.

10. exception Notification (after throwing advice): executes the notification after the pointcut throws an exception.

Second, the AOP implementation of spring interface

(a) See: Spring AOP (top)

(ii) analysis

1, to achieve dependency is troublesome, spring defines a bunch of notifications interface, as long as the implementation can be. such as the front notification interface Methodbeforeadvice

<span style= "FONT-SIZE:18PX;" >package Main.java.com.spring.aop.apj;import Java.lang.reflect.method;import org.springframework.aop.methodbeforeadvice;/** * Spring Interface Pre-notification * Basebeforeadvice * @title * @desc * @author Sam-sho * @Ja N. */public class Basebeforeadvice implements Methodbeforeadvice {    /**     * method: How to cut in <br>     * A RGS: Parameters of the Cut-in method <br>     * Target: Destination Object *    /@Override public    Void Before (method, object[] args, Object target) throws Throwable {        System.out.println ("=========== into Beforeadvice () ============ \ n");        System.out.print ("Ready to use" on "+ Target +" objects);        System.out.print (method + "approach to");        System.out.print (Args[0] + "' To delete! \ n ");        System.out.println ("To enter the Pointcut method \ n");}    } </span>

2. Need to specify tangency point: Implement Interface Methodbeforeadvice

<span style= "FONT-SIZE:18PX;" >/** * Defines a pointcut that specifies the corresponding method match. To be processed for the method <br> * Inherit the  Namematchmethodpointcut class to match the method name *  * @author  *  */public class Pointcut Extends Namematchmethodpointcut {    private static final long serialversionuid = 3990456017285944475L;    @SuppressWarnings ("Rawtypes")    @Override public    Boolean matches (method, Class targetclass) {        // Sets a single method to match        this.setmappedname ("delete");        Set multiple methods        to match string[] methods = {"Delete", "modify"};                You can also use "*" to do the matching symbol        //This.setmappedname ("get*");                This.setmappednames (methods);        Return Super.matches (method, Targetclass);}    } </span>

3, need to configure. Very troublesome.

Third, Spring uses ASPECTJ to realize AOP

(a) Source code

1. Business Class (target)

<span style= "FONT-SIZE:18PX;"  >package main.java.com.spring.aop.service;/** * Business interface * Personservice * @title * @desc * @author Sam-sho * @Jan 17, 2015 */public interface Personservice {/** * Save user entity * @param name */public void Save (String name);/** * Delete User entity * @param ID */p ublic void Delete (integer ID);/** * Query number is ID for use user name * @param ID */public String querypersonname (integer ID);/** * Update entity * @p Aram name * @param id */public void Update (String name, Integer ID);} </span>

<span style= "FONT-SIZE:18PX;" >package Main.java.com.spring.aop.service.impl;import main.java.com.spring.aop.service.personservice;/** * Business Implementation class * Persionserviceimpl * @title * @desc * @author Sam-sho * @Jan, */public class Personserviceimpl implements Personservice {@Overridepublic void Save (String name) {System.out.println ("I Am the Save () method");} @Overridepublic void Delete (Integer id) {System.out.println ("I am the Delete () method");} @Overridepublic String querypersonname (Integer id) {System.out.println ("I am the query () method"); return "XXX";} @Overridepublic void Update (String name, Integer ID) {System.out.println ("I Am the update () method");}} </span>

2, Slice class ( aspect: class internal definition of various notifications advice)

<span style= "FONT-SIZE:18PX;" >package Main.java.com.spring.aop.apj;import Org.aspectj.lang.joinpoint;import  org.aspectj.lang.proceedingjoinpoint;/** * * Aspectadvice * @title Slice class * @desc * @author Sam-sho * @Jan One, */public Class Aspectadvice {/** * pre-notification * * @param JP */public void Dobefore (Joinpoint jp) {Syste        M.out.println ("=========== into before advice============ \ n");        System.out.println ("Ready on" + Jp.gettarget (). GetClass () + "Object");        System.out.println (Jp.getsignature (). GetName () + "method to"); System.out.println (Jp.getargs () [0] + "' Delete!        \ n ");    System.out.println ("To enter the Pointcut method \ n"); }/** * Post notification * * @param JP * Connection point * @param result * return value */public        void Doafter (Joinpoint JP, String result) {System.out.println ("========== into after advice=========== \ n");        System.out.println ("The Pointcut method has been executed \ n");        System.out.print (Jp.getargs () [0] + "in"); SysteM.out.print (Jp.gettarget (). GetClass () + "on object");        System.out.print (Jp.getsignature (). GetName () + "method removed");    System.out.print ("Left only:" + result + "\ n"); }/** * Surround notification * * @param PJP * Connection point */public void Doaround (Proceedingjoinpoint pjp) t Hrows throwable {System.out.println ("=========== into around surround Method!        =========== \ n "); Call the target method before executing the action System.out.println ("Before calling the method: Execute!")        \ n ");        parameter of the calling method object[] args = Pjp.getargs ();        The method name of the call is String methods = Pjp.getsignature (). GetName ();        Gets the target objects object target = Pjp.gettarget ();        Executes the return value of the method: invokes the proceed () method, which triggers the Pointcut method to execute Object result = Pjp.proceed (); System.out.println ("Call method End: Execute after!")                \ n ");            System.out.println ("Output:" + args[0] + ";" + method + ";" + target + ";" + result + "\ n");        }/** * Exception notification * * @param JP * @param e */public void Dothrow (Joinpoint JP, Throwable e) { SysteM.out.println ("delete error"); }}</span>

3, configuration.

<span style= "FONT-SIZE:18PX;" > <!--declaring a business class bean--<bean id= "Personservice" class= "Main.java.com.spring.aop.service.impl.PersonServ     Iceimpl "/> <!--notice class--<bean id=" Aspectadvice "class=" Main.java.com.spring.aop.apj.AspectAdvice "/> <aop:config> <aop:aspect id= "Businessaspect" ref= "Aspectadvice" > <!--configuration Specifies the object to cut in--&gt            ; <aop:pointcut id= "point_cut" expression= "Execution (* main.java.com.spring.aop.service). *.*(..))" /> <!--match only the Add method as a pointcut-<!--<aop:pointcut id= "Except_add" expression= "Execution (* Aop.schema.*.add (..)) "            />-<!--pre-notification-<aop:before method= "Dobefore" pointcut-ref= "Point_cut"/> <!--post notification returning specify return parameters-<!--<aop:after-returning method= "Doafter" pointcut-ref= "Poin T_cut "returning=" result "/>-<!--surround-<!--<aop:arounD method= "Doaround" pointcut-ref= "Point_cut"/>-<!--throw--<!--<aop:after -throwing method= "Dothrow" pointcut-ref= "Point_cut" throwing= "E"/>-</aop:aspect> </aop:config ></span>

4, Test.

<span style= "FONT-SIZE:18PX;" > @Testpublic void Soptest () {ApplicationContext cxt = new Classpathxmlapplicationcontext (" Applicationaopcontext.xml "); Personservice Personservice = (personservice) cxt.getbean ("Personservice");p ersonservice.save ("Shaoxiaobao ...");// Taspectbusiness.delete ("Zhaoxioaniu");} </span>

Iv. Annotations for AOP

(i) Implementation of the configuration

1, the automatic scanning, annotations to implement the bean management and injection. (Targets and facets are managed by spring)

<span style= "FONT-SIZE:18PX;" >    <!--automatic scanning--    <context:component-scan base-package= "main.java.com.spring"/></span >

2. Development of AOP annotations

<span style= "FONT-SIZE:18PX;" >    <!--open AOP annotations--    <aop:aspectj-autoproxy/></span>

(b) Annotations implement slice classes.

<span style= "FONT-SIZE:18PX;" >package Main.java.com.spring.aop.apj;import Org.aspectj.lang.joinpoint;import Org.aspectj.lang.proceedingjoinpoint;import Org.aspectj.lang.annotation.afterreturning;import Org.aspectj.lang.annotation.afterthrowing;import Org.aspectj.lang.annotation.around;import Org.aspectj.lang.annotation.aspect;import Org.aspectj.lang.annotation.before;import Org.aspectj.lang.annotation.pointcut;import org.springframework.stereotype.Component; @Component//     Let Spring management bean@aspect//define the Slice class public class Annotationaspectadvice {/* * Specify pointcut matching expressions, note that it is declared in the form of a method.     * Analysis: * Execution is the method of weaving the language * First *: return any type * Main.java.com.spring.aop.service: Package. *  ..     : Service package and its child packages.     * Second *: Service package and any class under its sub-package.     * Third *: Any method of the service package and any class under its child package.     * (..): The parameters of the method are arbitrary. * Summary: The Main.java.com.spring.aop.service package and any of the classes under its sub-package are cut in/@Pointcut ("Execution (* main.java.com.spring.aop.serv Ice..    *.*(..))")     public void Anymethod () {}/** * pre-notification* * @param JP */@Before (value = "Execution" (* main.java.com.spring.aop.service).    *.*(..))")        public void Dobefore (Joinpoint jp) {System.out.println ("=========== into before advice============ \ n");        System.out.print ("Ready on" + Jp.gettarget (). GetClass () + "Object");        System.out.print (Jp.getsignature (). GetName () + "method to"); System.out.print (Jp.getargs () [0] + "' Delete!        \ n ");    System.out.println ("To enter the Pointcut method \ n"); }/** * Post notification * * @param JP * Connection point * @param result * return value */@AfterR Eturning (value = "Anymethod ()", returning = "result") public void Doafter (Joinpoint JP, String result) {System.        Out.println ("========== into after advice=========== \ n");        System.out.println ("The Pointcut method has been executed \ n");        System.out.print (Jp.getargs () [0] + "in");        System.out.print (Jp.gettarget (). GetClass () + "on object");        System.out.print (Jp.getsignature (). GetName () + "method removed"); System.out.print ("Leave only:" + Result + "\ n"); }/** * Surround notification * * @param PJP * Connection point */@Around (value = "Execution" (* main.java.com.spri Ng.aop.service.    *.*(..))") public void Doaround (Proceedingjoinpoint pjp) throws Throwable {System.out.println ("=========== into around surround Method!        =========== \ n "); Call the target method before executing the action System.out.println ("Before calling the method: Execute!")        \ n ");        parameter of the calling method object[] args = Pjp.getargs ();        The method name of the call is String methods = Pjp.getsignature (). GetName ();        Gets the target objects object target = Pjp.gettarget ();        Executes the return value of the method: invokes the proceed () method, which triggers the Pointcut method to execute Object result = Pjp.proceed ();        System.out.println ("Output:" + args[0] + ";" + method + ";" + target + ";" + result + "\ n"); System.out.println ("Call method End: Execute after!")    \ n "); }/** * Exception notification * * @param JP * @param e */@AfterThrowing (value = "Execution" (* main.java.com.spri Ng.aop.service.*.* (..)) ", throwing =" E ") public void Dothrow (Joinpoint JP, Throwable e) {System.out.println ("delete error"); }}</span>

1, Joinpoint: entry point, you can get the information to cut into the proxy object

1) Getargs (): Gets the method parameter.

2) Gettarget (): Gets the target object.

3) getsignature (): Get the method.

2, Proceedingjoinpoint: The use of the wrapping method.

1) Proceed (): The method that executes the target object.

3, Throwable: abnormal access.

Spring Note (c): an AOP explanation