Spring AOP 学习笔记

Jxi — Sun, 23 Aug 2009 14:52:00 GMT

AOP Aspect Oriented Programing 面向方面编程
AOP 术语
连接点:(Joinpoint)    程序执行的特定位置(类开始初始化前、类初始化后、调用前后、异常抛出后)
切点:   (PointCut)     程序类中客观存在的事物（类中的方法）
增强 :  (Advice)        置入到目标类Joinpint的一段代码
目标对象:(Target)   引介(Introduction) 织入(Weaving) 代理(Proxy) 切面(Aspect):切点和增强的组成

基础知识: Spring Aop :使用动态代理技术在运行期间织入增强代码
ProxyFactory 代理工厂采用JDK代理或CGLib代理技术
JDK 动态代理:
1.定义UserService接口函数:

public interface UserService {
public void addUser(int id);
}

2.UserServiceImpl

public class UserServiceImpl implements UserService{
public void addUser(int id){
System.out.println("添加一个用户中："+id);
}
}

3.ProxyHandler

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class ProxyHandler implements InvocationHandler{
   private Object target;
   public  ProxyHandler(Object target){
       this.target=target;
   }

public Object invoke(Object proxy, Method method, Object[] args)
        throws Throwable {
       System.out.println("添加用户前");
       Object obj=method.invoke(target,args);
       System.out.println("添加用户后");
       return obj;
}
}

TestProxyHandler

import java.lang.reflect.Proxy;

public class ProxyHandlerTest {
  public static void main(String args[]){
      UserService target=new UserServiceImpl();
      ProxyHandler handler=new ProxyHandler(target);
      UserService proxy=(UserService)Proxy.newProxyInstance(
        target.getClass().getClassLoader(),
        target.getClass().getInterfaces(),
        handler);
      proxy.addUser(100);
  }
}

CGLib 代理:
AddUserService接口:

package CGlib.Text.Service;

public interface AddUserService {
public void addUser(int id);
}

AddUserServiceImpl 实现类:

package CGlib.Text.Service;

public class AddUserServiceImpl implements AddUserService {

    public void addUser(int id) {
        System.out.println("添加用户ID中:"+id);
    }
}

CglibProxy 代理类:

package CGlib.Text.Service;

import java.lang.reflect.Method;

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class CglibProxy implements MethodInterceptor{
    private Enhancer enhancer=new Enhancer();
    @SuppressWarnings("unchecked")
    public Object getProxy(Class clazz){
        enhancer.setSuperclass(clazz);
        enhancer.setCallback(this);
        return enhancer.create();
    }

    public Object intercept(Object obj, Method method, Object[] args,
            MethodProxy proxy) throws Throwable {
        System.out.println("添加用户之前");
        System.out.print(method.getName());
        System.out.print(obj.getClass().getName()+"外加");
        System.out.print(args.getClass().getName());
        Object result=proxy.invokeSuper(obj, args);
        System.out.println("外加的参数"+args.toString());
        System.out.println("添加用户之后");
        // TODO Auto-generated method stub
        return result;
    }


}

CglibProxyTest:测试类

package CGlib.Text.Service;

public class CglibProxyTest {
    public static void main(String[] args){
        CglibProxy proxy=new CglibProxy();
        AddUserServiceImpl userService=
            (AddUserServiceImpl)proxy.getProxy(AddUserServiceImpl.class);
      userService.addUser(100);
    }

}

对JDK动态代理和Cglib动态代理的理解：
JDK 代理时性能高，但生成代理对象时运行性能较低
Cglib 代理时性能低，但生成代理对象时运行性能较高
所以：单例Singleton 时采用CGLib代理。

Jxi 2009-08-23 22:52 发表评论

Spring

Jxi — Sat, 25 Jul 2009 06:57:00 GMT

Spring

Important

Spring is an application framework. Unlike single-tier frameworks such as Struts or Hibernate, Spring aims to help structure whole applications in a consistent, productive manner, pulling together best-of-breed single-tier frameworks to create a coherent architecture.

Problems with the Traditional Approach to J2EE

传统J2EE方法存在的问题

J2EE applications tend to contain excessive amounts of "plumbing" code.多
Many J2EE applications use a distributed object model where this is inappropriate.杂
The EJB component model is unduly complex.不当
EJB is overused.过度使用
Many "J2EE design patterns" are not, in fact, design patterns, but workarounds for technology limitations.技术跟不上
J2EE applications are hard to unit test.测试难
Certain J2EE technologies have simply failed.

Enter Spring

接触Spring

Inversion of Control container:倒置控制
Aspect-Oriented Programming (AOP) framework:
Data access abstraction:
JDBC simplification:
Transaction management:
MVC web framework:
Simplification for working with JNDI, JTA, and other J2EE APIs:
Lightweight remoting:
JMS support:
JMX support:
Support for a comprehensive testing strategy for application developers:

The key Spring values can be summarized as follows:

· Spring is a non-invasive framework.非侵入

· Spring provides a consistent programming model, usable in any environment.

· Spring aims to promote code reuse.复用

· Spring aims to facilitate Object Oriented design in J2EE applications.

· Spring aims to facilitate good programming practice, such as programming to interfaces, rather than classes.面向接口

· Spring promotes pluggability.性能

· Spring facilitates the extraction of configuration values from Java code into XML or properties files.

· Spring is designed so that applications using it are as easy as possible to test.

· Spring is consistent.

· Spring promotes architectural choice.

· Spring does not reinvent the wheel.

Jxi 2009-07-25 14:57 发表评论

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Spring AOP 学习笔记

Spring