簡單動態代理實例（使用cglib）

       在持久層DAO層中，對數據庫操作有影響的增、刪、改都需要開啓事物，並在執行完增刪改之後要提交事物。但如果每個方法都這樣寫的話，那麼代碼變顯得冗餘，採用動態代理的方式來實現這種需求的話，可以使代碼更清晰簡潔，並且將事物和數據操作解耦。下面是簡單的模擬一下此案例，沒有真正的數據庫連接和事物，只是簡單的模擬。

1.Person.java

package cn.it.spring.proxy.dao;

public class Person {

	private Integer pid;
	private String pnameString;
//省略set和get方法，還有構造函數
}

2 . Transaction.java

package cn.it.spring.proxy.dao;
/**
 * 模擬事物類
 * @author Administrator
 *
 */
public class Transaction {
	/**
	 * 開啓事物
	 */
	public void beginTransaction(){
		System.out.println("beginTransaction");
	}
	/**
	 * 提交事物
	 */
	public void commit(){
		System.out.println("commit");
	}
}

3. PersonDaoImpl.java

package cn.it.spring.proxy.dao;

import java.util.ArrayList;
import java.util.List;
//此處沒有實現PersonDao接口
public class PersonDaoImpl{

	
	public void savePerson() {
		System.out.println("savePerson");
	}

	
	public void deletePerson() {
		System.out.println("deletePerson");
	}

	
	public void updatePerson() {
		System.out.println("updatePerson");

	}

	
	public List<Person> getPersons() {
		List<Person> persons = new ArrayList<>();
		Person person1 = new Person(1, "person1");
		Person person2 = new Person(2, "person2");
		persons.add(person1);
		persons.add(person2);
		return persons;
	}

}

4.MyInterceptor.java

package cn.it.spring.proxy.cglib;

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 MyInterceptor implements MethodInterceptor{
	private Object target;
	private Transaction transaction;
	
	public MyInterceptor(Object target, Transaction transaction) {
		super();
		this.target = target;
		this.transaction = transaction;
	}

	/**
	 * 產生代理對象
	 */
	public Object createProxy(){
		Enhancer enhancer = new Enhancer();
		enhancer.setCallback(this);//回調函數  攔截器
		enhancer.setSuperclass(this.target.getClass());//設置代理對象的父類
		return enhancer.create();
	}

	@Override
	public Object intercept(Object arg0, Method method, Object[] arg2, MethodProxy arg3) throws Throwable {
		// TODO Auto-generated method stub
				if(method.getName().equals("updatePerson")
						||method.getName().equals("savePerson")
						||method.getName().endsWith("deletePerson")){
					transaction.beginTransaction();
					method.invoke(target, arg2);//目標對象的目標方法
					transaction.commit();
					return null;
				}else{
					return method.invoke(this.target, arg2);//目標對象的目標方法
				}
		
	}

}

5. 測試類PersonDaoTest.java

package cn.it.spring.proxy.cglib;

import org.junit.Test;


public class PersonDaoImplTest {

	@Test
	public void test(){
		PersonDaoImpl target = new PersonDaoImpl();
		Transaction transaction = new Transaction();
		MyInterceptor interceptor = new MyInterceptor(target, transaction);
		
		PersonDaoImpl proxy = (PersonDaoImpl) interceptor.createProxy();
		
		proxy.savePerson();
		System.out.println("=============================");
		proxy.deletePerson();
		System.out.println("=============================");
		proxy.updatePerson();
		System.out.println("=============================");
		for(Person person : proxy.getPersons()){
			System.out.println(person.getPnameString());
		}
	}
}

6.結果