手動寫源碼---模擬實現動態代理

時間 2019-11-09

標籤手動源碼模擬實現動態代理简体版

原文原文鏈接

AOP的實現有兩種，一種是接口的實現，一種是產生本身實現，分別的表明爲JDK的Proxy和CGLIB的Proxyhtml

下面是模擬接口代理實現，經過模擬JDK的動態代理，更深入的理解java

經過動態代理能夠面向切面編程spring

1 定義被代理的對象和接口apache

Java代碼

public interface BookInterface {
void selling();
}

Java代碼

public interface PhoneInterface {
void selling();
}

Java代碼

public class Book implements BookInterface {
@Override
public void selling() {
System.out.println("books selling.....");
}
}

Java代碼

public class VivoPhone implements PhoneInterface {
@Override
public void selling() {
System.out.println("selling vivo x5");
}
}

2 定義切面類編程

Java代碼

public class TimeAspect {
static long bgn;
public static void before(){
bgn = System.currentTimeMillis();
System.out.println("begin time... " + bgn);
}
public static void after(){
long end = System.currentTimeMillis();
System.out.println("end time... " + (end-bgn));
}
}

Java代碼

public class LogAspect{
public static void before(){
System.out.println("begin log...");
}
public static void after(){
System.out.println("finish log...");
}
}

3 定義InvocationHander 代理接口ide

Java代碼

import java.lang.reflect.Method;
public interface InvocationHander {
public void invoke(Object o,Method m);
}

代理類（切面編程裏面也能夠作一些特殊的處理）函數

Java代碼

import java.lang.reflect.Method;
import jdkproxy.LogTranService;
import jdkproxy.TimeTranService;
public class ProxyHander implements InvocationHander {
private Object target;
public ProxyHander(Object target) {
this.target = target;
}
@Override
public void invoke(Object o, Method m) {
try {
TimeTranService.before();
if(!(o instanceof BookInterface)){//只有非BookInterface接口調用日誌
LogTranService.before();
}
m.invoke(target);
if(!(o instanceof BookInterface)){
LogTranService.after();
}
TimeTranService.after();
} catch (Exception e) {
e.printStackTrace();
}
}
}

動態代理類測試

Java代碼

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import javax.tools.JavaCompiler;
import javax.tools.JavaCompiler.CompilationTask;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import org.apache.commons.io.FileUtils;
public class Proxy {
/*
* 空的構造函數
*/
private Proxy(){
}
/*
* 返回代理類
*/
public static Object newProxyInstance(Class inter,InvocationHander h){
String packageName = inter.getPackage().getName();
// String temp = new String(packageName);
String proxyClassName = "$"+packageName.replace(".","_") + "_" + inter.getSimpleName() +"Proxy";
String InHanderPackage = h.getClass().getPackage().getName();
String rt = "\r\n";// 換行
String methodCode = "";
for (Method method:inter.getMethods()) {
methodCode+=" @Override"+rt+
" public void "+ method.getName()+"() {"+rt+
" try{"+rt+
" Method method = "+inter.getName()+".class.getMethod(\""
+ method.getName()+ "\");"+rt+
" h.invoke(this,method); "+rt+
" }catch(Exception e ){" +rt+
" e.printStackTrace();" +rt+
" }"+rt+
" }";
}
/*
* 總的java代碼
*/
String javaCode=
"package "+packageName+";"+rt+
"import "+InHanderPackage+".InvocationHander;"+rt+
"import java.lang.reflect.Method;"+rt+
"public class "+proxyClassName+" implements "+inter.getName()+" {"+rt+
" public "+proxyClassName+"("+InHanderPackage+".InvocationHander h) {"+rt+
" super();"+rt+
" this.h = h;"+rt+
" }"+rt+
" private "+InHanderPackage+".InvocationHander h;"+rt+
methodCode+rt+
"}";
/*
* 生成java文件
*/
// 生成文件路徑
String filename = System.getProperty("user.dir")+"/bin/"+packageName.replace(".", "//")+"/"+proxyClassName+".java";
File file = new File(filename);
try {
// 須要commons-io的jar方便的操做文件
FileUtils.writeStringToFile(file, javaCode);
} catch (IOException e) {
e.printStackTrace();
}
// 編譯拿到編譯器
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
// 文件管理
StandardJavaFileManager fileMgr = compiler.getStandardFileManager(null, null, null);
//獲取文件
Iterable units = fileMgr.getJavaFileObjects(filename);
// 編譯任務
CompilationTask t = compiler.getTask(null, fileMgr, null, null, null, units);
// call進行編譯
t.call();
try {
fileMgr.close();
} catch (IOException e) {
e.printStackTrace();
}
// load到內存
ClassLoader cl = ClassLoader.getSystemClassLoader();
try {
Class c = cl.loadClass(packageName+"."+proxyClassName);
Constructor ctr = c.getConstructor(InvocationHander.class);
return ctr.newInstance(h);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}

4 測試ui

Java代碼

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class TestProxy {
@Before
public void before(){
System.out.println("-----------------start-------------------");
}
@Test
public void test() {
Book book = new Book();
InvocationHander h = new ProxyHander(book);
BookInterface bi = (BookInterface)Proxy.newProxyInstance(BookInterface.class,h);
bi.selling(); // 沒有日誌打印
System.out.println("==================分割==============================");
PhoneInterface car = new VivoPhone();
h = new ProxyHander(car);
PhoneInterface pi = (PhoneInterface)Proxy.newProxyInstance(PhoneInterface.class,h);
pi.selling(); // 有日誌打印
}
@After
public void after(){
System.out.println("-----------------end-------------------");
}
}