java.lang.invoke.MethodHandles.Lookup#findVirtual ( )源码实例Demo

public static void main(String... args) throws Throwable {
    // Get a full power lookup
    Lookup lookup1 =  MethodHandles.lookup();
    MethodHandle mh1 = lookup1.findStatic(lookup1.lookupClass(),
                                          "foo",
                                          methodType(String.class));
    assertEquals((String) mh1.invokeExact(), foo());

    // access protected member
    MethodHandle mh2 = lookup1.findVirtual(java.lang.ClassLoader.class,
                                           "getPackage",
                                           methodType(Package.class, String.class));
    ClassLoader loader = ClassLoader.getPlatformClassLoader();
    Package pkg = (Package)mh2.invokeExact(loader, "java.lang");
    assertEquals(pkg.getName(), "java.lang");

    // MethodHandles.lookup will fail if it's called reflectively
    try {
        MethodHandles.class.getMethod("lookup").invoke(null);
    } catch (InvocationTargetException e) {
        if (!(e.getCause() instanceof IllegalArgumentException)) {
            throw e.getCause();
        }
    }
}
 

/**
 * Produces a {@link MethodHandle} using either the context or {@link #targetLoader} class
 * loader, depending on {@code target}.
 */
private MethodHandle toMethodHandle(Lookup lookup, Handle asmHandle, boolean target)
    throws ReflectiveOperationException {
  Class<?> owner = loadFromInternal(asmHandle.getOwner());
  MethodType signature =
      MethodType.fromMethodDescriptorString(
          asmHandle.getDesc(),
          target ? targetLoader : Thread.currentThread().getContextClassLoader());
  switch (asmHandle.getTag()) {
    case Opcodes.H_INVOKESTATIC:
      return lookup.findStatic(owner, asmHandle.getName(), signature);
    case Opcodes.H_INVOKEVIRTUAL:
    case Opcodes.H_INVOKEINTERFACE:
      return lookup.findVirtual(owner, asmHandle.getName(), signature);
    case Opcodes.H_INVOKESPECIAL: // we end up calling these using invokevirtual
      return lookup.findSpecial(owner, asmHandle.getName(), signature, owner);
    case Opcodes.H_NEWINVOKESPECIAL:
      return lookup.findConstructor(owner, signature);
    default:
      throw new UnsupportedOperationException("Cannot resolve " + asmHandle);
  }
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

private static MethodHandle mh(Lookup lookup, String name) {
  try {
    return lookup.findVirtual(org.slf4j.Logger.class, name, methodType(void.class, String.class, Throwable.class));
  } catch (NoSuchMethodException | IllegalAccessException e) {
    throw new AssertionError(e);
  }
}
 

private static MethodHandle mh(Lookup lookup, String name) {
  try {
    return lookup.findVirtual(ch.qos.logback.classic.Logger.class, name, methodType(void.class, String.class, Throwable.class));
  } catch (NoSuchMethodException | IllegalAccessException e) {
    throw new AssertionError(e);
  }
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

static MethodHandle lookupVirtual(Lookup lookup, Class<?> refc, String name, Class<?> rtype, Class<?>... ptypes) {
    try {
        return lookup.findVirtual(refc, name, MethodType.methodType(rtype, ptypes));
    } catch (NoSuchMethodException | IllegalAccessException e) {
        throw new AssertionError(e);
    }
}
 

static MethodHandle lookupVirtual(Lookup lookup, Class<?> refc, String name, Class<?> rtype, Class<?>... ptypes) {
    try {
        return lookup.findVirtual(refc, name, MethodType.methodType(rtype, ptypes));
    } catch (NoSuchMethodException | IllegalAccessException e) {
        throw new AssertionError(e);
    }
}
 

public static Class<?> handleCaller() throws Exception {
    Lookup lookup = MethodHandles.lookup();
    MethodHandle mh = lookup.findVirtual(StackWalker.class, "getCallerClass",
            MethodType.methodType(Class.class));
    try {
        return (Class<?>) mh.invoke(walker.get());
    } catch (Error | Exception x) {
        throw x;
    } catch(Throwable t) {
        throw new AssertionError(t);
    }
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

@Test
public void testUserClassInSignature() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

@Test
public void testUserClassInSignature() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

public void testUserClassInSignature0() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

@Test
public void testUserClassInSignature() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}
 

@Test
public void testUserClassInSignature() throws Throwable {
    if (CAN_SKIP_WORKING)  return;
    startTest("testUserClassInSignature");
    Lookup lookup = MethodHandles.lookup();
    String name; MethodType mt; MethodHandle mh;
    Object[] args;

    // Try a static method.
    name = "userMethod";
    mt = MethodType.methodType(Example.class, Object.class, String.class, int.class);
    mh = lookup.findStatic(lookup.lookupClass(), name, mt);
    assertEquals(mt, mh.type());
    assertEquals(Example.class, mh.type().returnType());
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);

    // Try a virtual method.
    name = "v2";
    mt = MethodType.methodType(Object.class, Object.class, int.class);
    mh = lookup.findVirtual(Example.class, name, mt);
    assertEquals(mt, mh.type().dropParameterTypes(0,1));
    assertTrue(mh.type().parameterList().contains(Example.class));
    args = randomArgs(mh.type().parameterArray());
    mh.invokeWithArguments(args);
    assertCalled(name, args);
}