Cglib動態代理詳解

發布時間：2023-09-30 21:09:54 作者：網友整理

CGLIB 簡介

為沒有實現接口的類提供代理
更好的性能

CGLIB 原理

原理：動態生成需要代理的子類，子類重寫代理類的非final方法。子類中采用方法攔截的奇數攔截所有父類的方法的調用，順勢織入橫切邏輯。
底層：使用ASM字節碼處理框架。
缺點：無法代理fianl方法。

CGLIB 應用

Spring AOP

CGLIB API

: 底層字節碼處理類，他們大部分與ASM有關系。
net.sf.cglib.transform: 編譯期或運行期類和類文件的轉換
net.sf.cglib.proxy: 實現創建代理和方法攔截器的類
net.sf.cglib.reflect: 實現快速反射和C#風格代理的類
net.sf.cglib.util: 集合排序等工具類
net.sf.cglib.beans: JAVABean相關的工具類

Code Example

Basic

package com.cclu.cglibproxy;
import java.util.HashMap;import java.util.Map;
/** * @author ChangCheng Lu * @date 2023/8/20 15:59 */public class UserService {
    private static final Map<String, String> nameMap;
    private static final Map<String, String> addressMap;
    static {        nameMap = new HashMap<>(3);        nameMap.put("1001", "木子");        nameMap.put("1002", "小一");        nameMap.put("1003", "阿同");
        addressMap = new HashMap<>(3);        addressMap.put("1001", "漣水");        addressMap.put("1002", "淮安");        addressMap.put("1003", "上海");    }
    public String getUserNameById(String userId) {        return nameMap.get(userId);    }
    public String getAddressById(String userId) {        return addressMap.get(userId);    }
}

package com.cclu.cglibproxy;
import net.sf.cglib.proxy.MethodInterceptor;import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
/** * @author ChangCheng Lu * @date 2023/8/20 16:04 */public class LogInterceptor implements MethodInterceptor {    @Override    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {        System.out.println("方法調用前...");        Object res = methodProxy.invokeSuper(o, objects);        System.out.println("方法調用后："+res);        return res;    }}

package com.cclu.cglibproxy;
import net.sf.cglib.proxy.Enhancer;
/** * @author ChangCheng Lu * @date 2023/8/20 16:10 */public class Client {    public static void mAIn(String[] args) {        Enhancer enhancer = new Enhancer();        enhancer.setSuperclass(UserService.class);        enhancer.setCallback(new LogInterceptor());        UserService userService = (UserService) enhancer.create();        userService.getUserNameById("1001");        userService.getAddressById("1003");    }}

Filter、FixedValue

package com.cclu.cglibproxy;
import java.util.HashMap;import java.util.Map;
/** * @author ChangCheng Lu * @date 2023/8/20 15:59 */public class UserService {
    private static final Map<String, String> nameMap;
    private static final Map<String, String> addressMap;
    static {        nameMap = new HashMap<>(3);        nameMap.put("1001", "木子");        nameMap.put("1002", "小一");        nameMap.put("1003", "阿同");
        addressMap = new HashMap<>(3);        addressMap.put("1001", "蘇州");        addressMap.put("1002", "淮安");        addressMap.put("1003", "上海");    }
    public String getUserNameById(String userId) {        return nameMap.get(userId);    }
    public String getAddressById(String userId) {        return addressMap.get(userId);    }
}

package com.cclu.cglibproxy;
import net.sf.cglib.proxy.CallbackFilter;
import java.lang.reflect.Method;
/** * @author ChangCheng Lu * @date 2023/8/20 16:35 */public class LogInterceptorFilter implements CallbackFilter {    @Override    public int accept(Method method) {        if (method.getName().equals("getUserNameById")) {            System.out.println("是不是木子？");            return 1;        } else if (method.getName().equals("getAddressById")) {            System.out.println("是不是阿同？");            return 2;        }        return 0;    }}

package com.cclu.cglibproxy;
import net.sf.cglib.proxy.FixedValue;
/** * @author ChangCheng Lu * @date 2023/8/20 17:44 */public class TargetResultFixed implements FixedValue {    @Override    public Object loadObject() throws Exception {        System.out.println("鎖定結果");        Object obj = "蘇州";        return obj;    }}

package com.cclu.cglibproxy;
import net.sf.cglib.proxy.Callback;import net.sf.cglib.proxy.Enhancer;import net.sf.cglib.proxy.NoOp;import org.junit.Test;
/** * @author ChangCheng Lu * @date 2023/8/20 17:32 */public class ProxyTest {
    @Test    public void filterTest() {        Enhancer enhancer = new Enhancer();        enhancer.setSuperclass(UserService.class);        enhancer.setCallbackFilter(new LogInterceptorFilter());        enhancer.setCallbacks(new Callback[]{NoOp.INSTANCE, new LogInterceptor(), new TargetResultFixed()});
        UserService userService = (UserService) enhancer.create();        System.out.println(userService);        System.out.println(userService.getUserNameById("1001"));        System.out.println(userService.getAddressById("1003"));    }
}