Byte Buddy 教程 Alpha

友情支持

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支付宝

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wx jikerizhi

公众号的微信号是: jikerizhi。因为众所周知的原因，有时图片加载不出来。如果图片加载不出来可以直接通过搜索微信号来查找我的公众号。

属性和方法

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String toString = new ByteBuddy()
  .subclass(Object.class)
  .name("example.Type")
  .make()
  .load(getClass().getClassLoader())
  .getLoaded()
  .newInstance() // Java reflection API
  .toString();

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String toString = new ByteBuddy()
  .subclass(Object.class)
  .name("example.Type")
  .method(named("toString")).intercept(FixedValue.value("Hello World!"))
  .make()
  .load(getClass().getClassLoader())
  .getLoaded()
  .newInstance()
  .toString();

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named("toString").and(returns(String.class)).and(takesArguments(0))

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class Foo {
  public String bar() { return null; }
  public String foo() { return null; }
  public String foo(Object o) { return null; }
}

Foo dynamicFoo = new ByteBuddy()
  .subclass(Foo.class)
  .method(isDeclaredBy(Foo.class)).intercept(FixedValue.value("One!"))
  .method(named("foo")).intercept(FixedValue.value("Two!"))
  .method(named("foo").and(takesArguments(1))).intercept(FixedValue.value("Three!"))
  .make()
  .load(getClass().getClassLoader())
  .getLoaded()
  .newInstance();

深入细看一个固定值

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new ByteBuddy()
  .subclass(Foo.class)
  .method(isDeclaredBy(Foo.class)).intercept(FixedValue.value(0))
  .make();

委托方法调用

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class Source {
  public String hello(String name) { return null; }
}

class Target {
  public static String hello(String name) {
    return "Hello " + name + "!";
  }
}

String helloWorld = new ByteBuddy()
  .subclass(Source.class)
  .method(named("hello")).intercept(MethodDelegation.to(Target.class))
  .make()
  .load(getClass().getClassLoader())
  .getLoaded()
  .newInstance()
  .hello("World");

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class Target {
  public static String intercept(String name) { return "Hello " + name + "!"; }
  public static String intercept(int i) { return Integer.toString(i); }
  public static String intercept(Object o) { return o.toString(); }
}

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void foo(Object o1, Object o2)

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void foo(@Argument(0) Object o1, @Argument(1) Object o2)

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class MemoryDatabase {
  public List<String> load(String info) {
    return Arrays.asList(info + ": foo", info + ": bar");
  }
}

class LoggerInterceptor {
  public static List<String> log(@SuperCall Callable<List<String>> zuper)
      throws Exception {
    System.out.println("Calling database");
    try {
      return zuper.call();
    } finally {
      System.out.println("Returned from database");
    }
  }
}

MemoryDatabase loggingDatabase = new ByteBuddy()
  .subclass(MemoryDatabase.class)
  .method(named("load")).intercept(MethodDelegation.to(LoggerInterceptor.class))
  .make()
  .load(getClass().getClassLoader())
  .getLoaded()
  .newInstance();

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class LoggingMemoryDatabase extends MemoryDatabase {

  private class LoadMethodSuperCall implements Callable {

    private final String info;
    private LoadMethodSuperCall(String info) {
      this.info = info;
    }

    @Override
    public Object call() throws Exception {
      return LoggingMemoryDatabase.super.load(info);
    }
  }

  @Override
  public List<String> load(String info) {
    return LoggerInterceptor.log(new LoadMethodSuperCall(info));
  }
}

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class ChangingLoggerInterceptor {
  public static List<String> log(String info, @Super MemoryDatabase zuper) {
    System.out.println("Calling database");
    try {
      return zuper.load(info + " (logged access)");
    } finally {
      System.out.println("Returned from database");
    }
  }
}

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class Loop {
  public String loop(String value) { return value; }
  public int loop(int value) { return value; }
}

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class Interceptor {
  @RuntimeType
  public static Object intercept(@RuntimeType Object value) {
    System.out.println("Invoked method with: " + value);
    return value;
  }
}

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interface Forwarder<T, S> {
  T to(S target);
}

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class ForwardingLoggerInterceptor {

  private final MemoryDatabase memoryDatabase; // constructor omitted

  public List<String> log(@Pipe Forwarder<List<String>, MemoryDatabase> pipe) {
    System.out.println("Calling database");
    try {
      return pipe.to(memoryDatabase);
    } finally {
      System.out.println("Returned from database");
    }
  }
}

MemoryDatabase loggingDatabase = new ByteBuddy()
  .subclass(MemoryDatabase.class)
  .method(named("load")).intercept(MethodDelegation.withDefaultConfiguration()
    .withBinders(Pipe.Binder.install(Forwarder.class)))
    .to(new ForwardingLoggerInterceptor(new MemoryDatabase()))
  .make()
  .load(getClass().getClassLoader())
  .getLoaded()
  .newInstance();

调用超类方法

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new ByteBuddy()
  .subclass(Object.class)
  .make()

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new ByteBuddy()
  .subclass(Object.class, ConstructorStrategy.Default.IMITATE_SUPER_TYPE)
  .make()

调用默认方法

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interface First {
  default String qux() { return "FOO"; }
}

interface Second {
  default String qux() { return "BAR"; }
}

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new ByteBuddy(ClassFileVersion.JAVA_V8)
  .subclass(Object.class)
  .implement(First.class)
  .implement(Second.class)
  .method(named("qux")).intercept(DefaultMethodCall.prioritize(First.class))
  .make()

调用特定方法

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public class SampleClass {
  public SampleClass(int unusedValue) {
    super();
  }
}

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new ByteBuddy()
  .subclass(Object.class, ConstructorStrategy.Default.NO_CONSTRUCTORS)
  .defineConstructor(Arrays.<Class<?>>asList(int.class), Visibility.PUBLIC)
  .intercept(MethodCall.invoke(Object.class.getDeclaredConstructor()))
  .make()

访问属性

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class UserType {
  public String doSomething() { return null; }
}

interface Interceptor {
  String doSomethingElse();
}

interface InterceptionAccessor {
  Interceptor getInterceptor();
  void setInterceptor(Interceptor interceptor);
}

interface InstanceCreator {
  Object makeInstance();
}

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Class<? extends UserType> dynamicUserType = new ByteBuddy()
  .subclass(UserType.class)
    .method(not(isDeclaredBy(Object.class)))
    .intercept(MethodDelegation.toField("interceptor"))
  .defineField("interceptor", Interceptor.class, Visibility.PRIVATE)
  .implement(InterceptionAccessor.class).intercept(FieldAccessor.ofBeanProperty())
  .make()
  .load(getClass().getClassLoader())
  .getLoaded();

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InstanceCreator factory = new ByteBuddy()
  .subclass(InstanceCreator.class)
    .method(not(isDeclaredBy(Object.class)))
    .intercept(MethodDelegation.construct(dynamicUserType))
  .make()
  .load(dynamicUserType.getClassLoader())
  .getLoaded().newInstance();

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class HelloWorldInterceptor implements Interceptor {
  @Override
  public String doSomethingElse() {
    return "Hello World!";
  }
}

UserType userType = (UserType) factory.makeInstance();
((InterceptionAccessor) userType).setInterceptor(new HelloWorldInterceptor());

Byte Buddy 教程 ^Alpha

友情支持

属性和方法

深入细看一个固定值

委托方法调用

调用超类方法

调用默认方法

调用特定方法

访问属性

杂项