//公共抽象接口 - 出租的人
public interface Person {
 void rent();
}

//真實(shí)角色 - 房東
public class Landlord implements Person{
 public void rent() {
 System.out.println("客官請進(jìn)，我家的房子又大又便宜，來租我的吧...");
 }
}

//代理角色 - 房產(chǎn)中介
public class Agent implements Person{
 Person landlord;

 public Agent(Person landlord) {
 this.landlord = landlord;
 }

 public void rent() {
 	//前置處理
 System.out.println("經(jīng)過前期調(diào)研，西湖邊的房子環(huán)境挺好的...");
 	//委托真實(shí)角色處理
 landlord.rent();
 	//后置處理
 System.out.println("房子漏水，幫你聯(lián)系維修人員...");
 }
}

//客戶端
public class Client {
 public static void main(String[] args) {
 Person landlord = new Landlord();
 Person agent = new Agent(landlord);
 agent.rent();
 }
}

//輸出結(jié)果：
經(jīng)過前期調(diào)研，西湖邊的房子環(huán)境挺好的...
客官請進(jìn)，我家的房子又大又便宜，來租我的吧...
房子漏水，幫你聯(lián)系維修人員...

public class Landlord01 implements Person{
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

public class Landlord02 implements Person{
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

public class Landlord03 implements Person{
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

... 可能還有很多房東，省略

public class Agent01 implements Person{
 Person landlord01;
 //省略構(gòu)造器等信息
 public void rent() {landlord01.rent();}
}
public class Agent02 implements Person{
 Person landlord02;
 //省略構(gòu)造器等信息
 public void rent() {landlord02.rent();}
}
public class Agent03 implements Person{
 Person landlord03;
 //省略構(gòu)造器等信息
 public void rent() {landlord03.rent();}
}

...

public class Landlord01 implements Person{
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

public class Landlord02 implements Person{
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

public class Landlord03 implements Person{
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

public class Agent implements Person{
 Person landlord01;
 	Person landlord02;
 	Person landlord03;
 //省略構(gòu)造器等信息
 public void rent01() { ... }
 	public void rent02() { ... }
 	public void rent03() { ... }
}

//公共抽象接口和真實(shí)角色和靜態(tài)代理的例子中代碼相同，省略

//自定義調(diào)用處理器
public class RentHandler implements InvocationHandler {
 Person landlord;
 
 public RentHandler(Person landlord) {
 this.landlord = landlord;
 }
	//客戶端對代理對象發(fā)起的所有請求都會(huì)被委托給該方法
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 	//前置處理
 System.out.println("經(jīng)過前期調(diào)研，西湖邊的房子環(huán)境挺好的...");
 	//委托給真實(shí)角色處理業(yè)務(wù)邏輯
 method.invoke(landlord, args);
 	//后置處理
 System.out.println("房子漏水，幫你聯(lián)系維修人員...");
 return null;
 }
}

//客戶端
public class Client2 {
 public static void main(String[] args) {
 Person landlord = new Landlord();
 Person proxy = (Person) Proxy.newProxyInstance(
  ClassLoader.getSystemClassLoader(), //加載代理類的類加載器
  new Class[]{Person.class}, //代理的接口
  new RentHandler(landlord));//自定義調(diào)用處理器實(shí)現(xiàn)
 proxy.rent();
 }
}

//輸出結(jié)果：
經(jīng)過前期調(diào)研，西湖邊的房子環(huán)境挺好的...
客官請進(jìn)，我家的房子又大又便宜，來租我的吧...
房子漏水，幫你聯(lián)系維修人員...

public static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h) throws IllegalArgumentException {
		... //省略一些非空校驗(yàn)，權(quán)限校驗(yàn)的邏輯
 //返回一個(gè)代理類，這個(gè)是整個(gè)方法的核心，后續(xù)會(huì)做詳細(xì)剖析
 Class<?> cl = getProxyClass0(loader, intfs);
		//使用反射獲取其有參構(gòu)造器，constructorParams是定義在Proxy類中的字段，值為{InvocationHandler.class}
 final Constructor<?> cons = cl.getConstructor(constructorParams);
		//使用返回創(chuàng)建代理對象
 return cons.newInstance(new Object[]{h});

}

private static Class<?> getProxyClass0(ClassLoader loader, Class<?>... interfaces) {
 if (interfaces.length > 65535) {
  throw new IllegalArgumentException("interface limit exceeded");
 }
 return proxyClassCache.get(loader, interfaces);
}

public V get(K key, P parameter){
 ... //省略大量的緩存操作
 while (true) {
 if (supplier != null) {
 V value = supplier.get();
 if (value != null) {
  return value;	★
 }
 }
 if (factory == null) {
 factory = new WeakCache.Factory(key, parameter, subKey, valuesMap); ▲
 }

 if (supplier == null) {
 supplier = valuesMap.putIfAbsent(subKey, factory);
 if (supplier == null) {
  supplier = factory;
 }
 } else {
 if (valuesMap.replace(subKey, supplier, factory)) {
  supplier = factory;
 } else {
  supplier = valuesMap.get(subKey);
 }
 }
 }
}

public synchronized V get() {
		... //省略一些緩存操作
 V value = null;
 value = Objects.requireNonNull(valueFactory.apply(key, parameter));
 ... //省略一些緩存操作
 return value;
}

Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
		//對每一個(gè)指定的Class校驗(yàn)其是否能被指定的類加載器加載以及校驗(yàn)是否是接口，動(dòng)態(tài)代理只能對接口代理，至于原因，后面會(huì)說。
 for (Class<?> intf : interfaces) {
  Class<?> interfaceClass = null;
  interfaceClass = Class.forName(intf.getName(), false, loader);
  if (interfaceClass != intf) {
  throw new IllegalArgumentException(
   intf + " is not visible from class loader");
  }  	
  if (!interfaceClass.isInterface()) {
  throw new IllegalArgumentException(
   interfaceClass.getName() + " is not an interface");
  }
  if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
  throw new IllegalArgumentException(
   "repeated interface: " + interfaceClass.getName());
  }
 }
		//下面這一大段是用來指定生成的代理類的包信息
		//如果全是public的，就是用默認(rèn)的com.sun.proxy，
		//如果有非public的，所有的非public接口必須處于同一級別包下面，而該包路徑也會(huì)成為生成的代理類的包。
 String proxyPkg = null; 
 int accessFlags = Modifier.PUBLIC | Modifier.FINAL;

 for (Class<?> intf : interfaces) {
  int flags = intf.getModifiers();
  if (!Modifier.isPublic(flags)) {
  accessFlags = Modifier.FINAL;
  String name = intf.getName();
  int n = name.lastIndexOf('.');
  String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
  if (proxyPkg == null) {
   proxyPkg = pkg;
  } else if (!pkg.equals(proxyPkg)) {
   throw new IllegalArgumentException(
    "non-public interfaces from different packages");
  }
  }
 }

 if (proxyPkg == null) {
  proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
 }

 long num = nextUniqueNumber.getAndIncrement();
				//代理類最后生成的名字是包名+$Proxy+一個(gè)數(shù)字
 String proxyName = proxyPkg + proxyClassNamePrefix + num;
				//生成代理類的核心
 byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
  proxyName, interfaces, accessFlags);★
  return defineClass0(loader, proxyName,
   proxyClassFile, 0, proxyClassFile.length);
 }

 public static byte[] generateProxyClass(final String name, Class<?>[] interfaces, int accessFlags) {
 ProxyGenerator gen = new ProxyGenerator(name, interfaces, accessFlags);
 final byte[] classFile = gen.generateClassFile();

 if (saveGeneratedFiles) {
  //省略一堆IO操作
 }
 return classFile;
 }

private final static boolean saveGeneratedFiles =
 java.security.AccessController.doPrivileged(
  new GetBooleanAction("sun.misc.ProxyGenerator.saveGeneratedFiles")).booleanValue();

private byte[] generateClassFile() {
 addProxyMethod(hashCodeMethod, Object.class);
 addProxyMethod(equalsMethod, Object.class);
 addProxyMethod(toStringMethod, Object.class);
 for (Class<?> intf : interfaces) {
  for (Method m : intf.getMethods()) {
  addProxyMethod(m, intf);
  }
 }
 for (List<ProxyGenerator.ProxyMethod> sigmethods : proxyMethods.values()) {
  checkReturnTypes(sigmethods);
 }
 methods.add(generateConstructor());

 for (List<ProxyGenerator.ProxyMethod> sigmethods : proxyMethods.values()) {
  for (ProxyGenerator.ProxyMethod pm : sigmethods) {

  fields.add(new ProxyGenerator.FieldInfo(pm.methodFieldName,
   "Ljava/lang/reflect/Method;",
   ACC_PRIVATE | ACC_STATIC));

  methods.add(pm.generateMethod());
  }
 }
 methods.add(generateStaticInitializer());
 if (methods.size() > 65535) {
  throw new IllegalArgumentException("method limit exceeded");
 }
 if (fields.size() > 65535) {
  throw new IllegalArgumentException("field limit exceeded");
 }

 cp.getClass(dotToSlash(className));
 cp.getClass(superclassName);
 for (Class<?> intf : interfaces) {
  cp.getClass(dotToSlash(intf.getName()));
 }

 cp.setReadOnly();

 ByteArrayOutputStream bout = new ByteArrayOutputStream();
 DataOutputStream dout = new DataOutputStream(bout);

 dout.writeInt(0xCAFEBABE);
 // u2 minor_version;
 dout.writeShort(CLASSFILE_MINOR_VERSION);
 // u2 major_version;
 dout.writeShort(CLASSFILE_MAJOR_VERSION);

 cp.write(dout);  // (write constant pool)

 // u2 access_flags;
 dout.writeShort(accessFlags);
 // u2 this_class;
 dout.writeShort(cp.getClass(dotToSlash(className)));
 // u2 super_class;
 dout.writeShort(cp.getClass(superclassName));

 // u2 interfaces_count;
 dout.writeShort(interfaces.length);
 // u2 interfaces[interfaces_count];
 for (Class<?> intf : interfaces) {
  dout.writeShort(cp.getClass(
   dotToSlash(intf.getName())));
 }

 // u2 fields_count;
 dout.writeShort(fields.size());
 // field_info fields[fields_count];
 for (ProxyGenerator.FieldInfo f : fields) {
  f.write(dout);
 }

 // u2 methods_count;
 dout.writeShort(methods.size());
 // method_info methods[methods_count];
 for (ProxyGenerator.MethodInfo m : methods) {
  m.write(dout);
 }
 // u2 attributes_count;
 dout.writeShort(0);

 return bout.toByteArray();
 }

public class Client2 {
 public static void main(String[] args) {
 	//加入該屬性并設(shè)置為true
 System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
 Person landlord = new Landlord();
 Person proxy = (Person) Proxy.newProxyInstance(ClassLoader.getSystemClassLoader(), new Class[]{Person.class}, new RentHandler(landlord));
 proxy.rent();
 }
}

public final class $Proxy0 extends Proxy implements Person { ★
 private static Method m1;
 private static Method m3;
 private static Method m2;
 private static Method m0;

 public $Proxy0(InvocationHandler var1) throws { ②
 super(var1);
 }

 public final boolean equals(Object var1) throws {	④
 return (Boolean) super.h.invoke(this, m1, new Object[]{var1});
 }

 public final void rent() throws {	③
 super.h.invoke(this, m3, (Object[]) null);
 }

 public final String toString() throws {	④
 return (String) super.h.invoke(this, m2, (Object[]) null);
 }

 public final int hashCode() throws {	④
 return (Integer) super.h.invoke(this, m0, (Object[]) null);
 }

 static {	①
 m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
 m3 = Class.forName("com.dujc.mybatis.proxy.Person").getMethod("rent");
 m2 = Class.forName("java.lang.Object").getMethod("toString");
 m0 = Class.forName("java.lang.Object").getMethod("hashCode");
 }
}

public final class ConnectionLogger extends BaseJdbcLogger implements InvocationHandler { ❶

 private final Connection connection;	

 private ConnectionLogger(Connection conn, Log statementLog, int queryStack) {
  super(statementLog, queryStack);
  this.connection = conn;	❷
 }

 @Override
 public Object invoke(Object proxy, Method method, Object[] params)	❸
   throws Throwable {
  if (Object.class.equals(method.getDeclaringClass())) {
   return method.invoke(this, params);
  }
  if ("prepareStatement".equals(method.getName())) {
   if (isDebugEnabled()) {
    debug(" Preparing: " + removeBreakingWhitespace((String) params[0]), true);
   }
   PreparedStatement stmt = (PreparedStatement) method.invoke(connection, params);
   stmt = PreparedStatementLogger.newInstance(stmt, statementLog, queryStack);
   return stmt;
  } else if ("prepareCall".equals(method.getName())) {
   if (isDebugEnabled()) {
    debug(" Preparing: " + removeBreakingWhitespace((String) params[0]), true);
   }
   PreparedStatement stmt = (PreparedStatement) method.invoke(connection, params);
   stmt = PreparedStatementLogger.newInstance(stmt, statementLog, queryStack);
   return stmt;
  } else if ("createStatement".equals(method.getName())) {
   Statement stmt = (Statement) method.invoke(connection, params);
   stmt = StatementLogger.newInstance(stmt, statementLog, queryStack);
   return stmt;
  } else {
   return method.invoke(connection, params);
  }
 }

 public static Connection newInstance(Connection conn, Log statementLog, int queryStack) {
  InvocationHandler handler = new ConnectionLogger(conn, statementLog, queryStack);
  ClassLoader cl = Connection.class.getClassLoader();
  return (Connection) Proxy.newProxyInstance(cl, new Class[]{Connection.class}, handler);
 }
}

public final class PreparedStatementLogger extends BaseJdbcLogger implements InvocationHandler {

 private final PreparedStatement statement;

 private PreparedStatementLogger(PreparedStatement stmt, Log statementLog, int queryStack) {
  super(statementLog, queryStack);
  this.statement = stmt;
 }

 @Override
 public Object invoke(Object proxy, Method method, Object[] params) throws Throwable {
  if (Object.class.equals(method.getDeclaringClass())) {
   return method.invoke(this, params);
  }
  if (EXECUTE_METHODS.contains(method.getName())) {
   if (isDebugEnabled()) {
    debug("Parameters: " + getParameterValueString(), true);
   }
   clearColumnInfo();
   if ("executeQuery".equals(method.getName())) {
    ResultSet rs = (ResultSet) method.invoke(statement, params);
    return rs == null ? null : ResultSetLogger.newInstance(rs, statementLog, queryStack);
   } else {
    return method.invoke(statement, params);
   }
  } else if (SET_METHODS.contains(method.getName())) {
   if ("setNull".equals(method.getName())) {
    setColumn(params[0], null);
   } else {
    setColumn(params[0], params[1]);
   }
   return method.invoke(statement, params);
  } else if ("getResultSet".equals(method.getName())) {
   ResultSet rs = (ResultSet) method.invoke(statement, params);
   return rs == null ? null : ResultSetLogger.newInstance(rs, statementLog, queryStack);
  } else if ("getUpdateCount".equals(method.getName())) {
   int updateCount = (Integer) method.invoke(statement, params);
   if (updateCount != -1) {
    debug(" Updates: " + updateCount, false);
   }
   return updateCount;
  } else {
   return method.invoke(statement, params);
  }
 }

 public static PreparedStatement newInstance(PreparedStatement stmt, Log statementLog, int queryStack) {
  InvocationHandler handler = new PreparedStatementLogger(stmt, statementLog, queryStack);
  ClassLoader cl = PreparedStatement.class.getClassLoader();
  return (PreparedStatement) Proxy.newProxyInstance(cl, new Class[]{PreparedStatement.class, CallableStatement.class}, handler);
 }
}