1、请总结静态代理和动态代理的根本区别。
a.静态代理只能通过手动完成代理操作，如果被代理类增加了新的方法，代理类需要同步增加，违背开闭原则；
b.动态代理采用在运行时动态生成代码的方式，取消了对被代理类的扩展限制，遵循开闭原则；
c.若动态代理要对目标类的增强逻辑进行扩展，结合策略模式，只需要新增策略类便可完成，无须修改代理类的代码。
2、继续完成手写Proxy类中带参数方法的代理实现。
public interface IPerson {
public void findLove(String request);
}
public class ZhangSan implements IPerson {
@Override
public void findLove(String request) {
System.out.println("儿子要求：" + request);
}
}
public interface SzpInvocationHandler {
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable;
}
public class SzpClassLoader extends ClassLoader {
private File classPathFile;
public SzpClassLoader(){
String classPath = SzpClassLoader.class.getResource("").getPath();
this.classPathFile = new File(classPath);
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
String className = SzpClassLoader.class.getPackage().getName() + "." +name;
if(classPathFile != null){
File classFile = new File(classPathFile, name.replaceAll("\\.", "/") + ".class");
if(classFile.exists()){
FileInputStream in = null;
ByteArrayOutputStream out = null;
try {
in = new FileInputStream(classFile);
out = new ByteArrayOutputStream();
byte[] buff = new byte[1024];
int len;
while((len = in.read(buff)) != -1){
out.write(buff,0, len);
}
return defineClass(className, out.toByteArray(), 0, out.size());
}catch (Exception e){
e.printStackTrace();
}finally {
if(null != in){
try {
in.close();
}catch (IOException e){
e.printStackTrace();
}
}
if(null != out){
try {
in.close();
}catch (IOException e){
e.printStackTrace();
}
}
}
}
}
return null;
}
}
public class SzpProxy {
private static final String ln = "\r\n";
public static Object newProxyInstance(SzpClassLoader loader, Class<?>[] interfaces, SzpInvocationHandler h) {
try {
//1.动态生成源码.java文件
String src = generateSrc(interfaces);
System.out.println(src);
//2.java文件输出到磁盘
String filePath = SzpProxy.class.getResource("").getPath();
File f = new File(filePath + "$Proxy0.java");
FileWriter fw = new FileWriter(f);
fw.write(src);
fw.flush();
fw.close();
//3.把生成的.java文件编译成.class文件
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager manage = compiler.getStandardFileManager(null, null, null);
Iterable<? extends JavaFileObject> iterable = manage.getJavaFileObjects(f);
JavaCompiler.CompilationTask task = compiler.getTask(null, manage, null, null, null, iterable);
task.call();
manage.close();
//4.把编译生成的.class文件加载到jvm中
Class<?> proxyClass = loader.findClass("$Proxy0");
Constructor<?> c = proxyClass.getConstructor(SzpInvocationHandler.class);
f.delete();
//5.返回字节码重组以后的新的代理对象
return c.newInstance(h);
}catch (Exception e){
e.printStackTrace();
}
return null;
}
private static String generateSrc(Class<?>[] interfaces) {
StringBuffer sb = new StringBuffer();
sb.append("package com.lufax.uic.proxy.szpproxy;" + ln);
sb.append("import com.lufax.uic.proxy.IPerson;" + ln);
sb.append("import java.lang.reflect.*;" + ln);
sb.append("public class $Proxy0 implements " + interfaces[0].getName() + "{" + ln);
sb.append("SzpInvocationHandler h;" + ln);
sb.append("public $Proxy0(SzpInvocationHandler h){" + ln);
sb.append("this.h = h;" +ln);
sb.append("}" + ln);
for (Method m : interfaces[0].getMethods()){
Class<?>[] params = m.getParameterTypes();
StringBuffer paramNames = new StringBuffer();
StringBuffer paramValues = new StringBuffer();
StringBuffer paramClasses = new StringBuffer();
for (int i=0;i<params.length;i++){
Class clazz = params[i];
String type = clazz.getName();
String paramName = toLowerFirstCase(clazz.getSimpleName());
paramNames.append(type + " " + paramName);
paramValues.append(paramName);
paramClasses.append(type + ".class");
if(i>0 && i<params.length-1){
paramNames.append(",");
paramValues.append(",");
paramClasses.append(",");
}
}
sb.append("public " + m.getReturnType().getName() + " " + m.getName() + "(" + paramNames.toString() + "){" + ln);
sb.append("try{" + ln);
sb.append("Method m =" + interfaces[0].getName() + ".class.getMethod(\"" + m.getName() +"\",new Class[]{" + paramClasses.toString() +"});" + ln);
sb.append((hasReturnValue(m.getReturnType()) ? "return " : "") + getCaseCode("this.h.invoke(this,m,new Object[]{" + paramValues + "})", m.getReturnType()) + ";" + ln);
sb.append("}catch(Error _ex){}");
sb.append("catch(Throwable e){" + ln);
sb.append("throw new UndeclaredThrowableException(e);" + ln);
sb.append("}");
sb.append(getReturnEmptyCode(m.getReturnType()));
sb.append("}" + ln);
}
sb.append("}" + ln);
return sb.toString();
}
private static boolean hasReturnValue(Class<?> clazz){
return clazz != void.class;
}
private static Map<Class, Class> mappings = new HashMap<Class, Class>();
static{
mappings.put(int.class , Integer.class);
}
private static String getCaseCode(String code, Class<?> returnClass){
if(mappings.containsKey(returnClass)){
return "((" + mappings.get(returnClass).getName() + ")" + code + ")." + returnClass.getSimpleName()+"Value()";
}
return code;
}
private static String getReturnEmptyCode(Class<?> returnType) {
if(mappings.containsKey(returnType)){
return "return 0;";
}else if(returnType == void.class){
return "";
}else{
return "return null;";
}
}
private static String toLowerFirstCase(String src) {
char[] chars = src.toCharArray();
chars[0] += 32;
return String.valueOf(chars);
}
}
public class SzpMeipo implements SzpInvocationHandler {
private Object target;
public Object getInstance(Object target){
this.target = target;
Class<?> clazz = target.getClass();
Object o = SzpProxy.newProxyInstance(new SzpClassLoader(), clazz.getInterfaces(), this);
return o;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
before();
Object result = method.invoke(this.target, args);
after();
return result;
}
private void before(){
System.out.println("我是媒婆,已经收集到你的需求,开始物色");
}
private void after(){
System.out.println("双方同意,开始交往");
}
}
public class ClientTest {
public static void main(String[] args) {
try {
IPerson obj = (IPerson)new SzpMeipo().getInstance(new ZhangSan());
obj.findLove("有车有房高学历");
}catch (Exception e){
e.printStackTrace();
}
}
}