org.kitesdk.compat.DynMethods Maven / Gradle / Ivy
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/*
* Copyright 2013 Cloudera Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.kitesdk.compat;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;
import java.util.Arrays;
public class DynMethods {
/**
* Convenience wrapper class around {@link java.lang.reflect.Method}.
*
* Allows callers to invoke the wrapped method with all Exceptions wrapped by
* RuntimeException, or with a single Exception catch block.
*/
public static class UnboundMethod {
private final Method method;
private final String name;
private final int argLength;
UnboundMethod(Method method, String name) {
this.method = method;
this.name = name;
this.argLength = (method == null || method.isVarArgs()) ? -1 :
method.getParameterTypes().length;
}
@SuppressWarnings("unchecked")
public R invokeChecked(Object target, Object... args) throws Exception {
try {
if (argLength < 0) {
return (R) method.invoke(target, args);
} else {
return (R) method.invoke(target, Arrays.copyOfRange(args, 0, argLength));
}
} catch (InvocationTargetException e) {
// rethrow the cause is an exception
Throwables.propagateIfPossible(e.getCause(), Exception.class);
// otherwise, propagate the throwable
throw Throwables.propagate(e.getCause());
}
}
public R invoke(Object target, Object... args) {
try {
return this.invokeChecked(target, args);
} catch (Exception e) {
throw Throwables.propagate(e);
}
}
/**
* Returns this method as a BoundMethod for the given receiver.
*
* @param receiver an Object to receive the method invocation
* @return a {@link BoundMethod} for this method and the receiver
* @throws IllegalStateException if the method is static
* @throws IllegalArgumentException if the receiver's class is incompatible
*/
public BoundMethod bind(Object receiver) {
Preconditions.checkState(!isStatic(),
"Cannot bind static method " + method.toGenericString());
Preconditions.checkArgument(
method.getDeclaringClass().isAssignableFrom(receiver.getClass()),
"Cannot bind " + method.toGenericString() + " to instance of " +
receiver.getClass());
return new BoundMethod(this, receiver);
}
/**
* @return whether the method is a static method
*/
public boolean isStatic() {
return Modifier.isStatic(method.getModifiers());
}
/**
* Returns this method as a StaticMethod.
*
* @return a {@link StaticMethod} for this method
* @throws IllegalStateException if the method is not static
*/
public StaticMethod asStatic() {
Preconditions.checkState(isStatic(), "Method is not static");
return new StaticMethod(this);
}
public String toString() {
return Objects.toStringHelper(this)
.add("name", name)
.add("method", method.toGenericString())
.toString();
}
/**
* Singleton {@link UnboundMethod}, performs no operation and returns null.
*/
private static UnboundMethod NOOP = new UnboundMethod(null, "NOOP") {
@Override
public R invokeChecked(Object target, Object... args) throws Exception {
return null;
}
@Override
public BoundMethod bind(Object receiver) {
return new BoundMethod(this, receiver);
}
@Override
public StaticMethod asStatic() {
return new StaticMethod(this);
}
@Override
public boolean isStatic() {
return true;
}
@Override
public String toString() {
return Objects.toStringHelper(this)
.add("name", "noop")
.toString();
}
};
}
public static class BoundMethod {
private final UnboundMethod method;
private final Object receiver;
private BoundMethod(UnboundMethod method, Object receiver) {
this.method = method;
this.receiver = receiver;
}
public R invokeChecked(Object... args) throws Exception {
return method.invokeChecked(receiver, args);
}
public R invoke(Object... args) {
return method.invoke(receiver, args);
}
}
public static class StaticMethod {
private final UnboundMethod method;
private StaticMethod(UnboundMethod method) {
this.method = method;
}
public R invokeChecked(Object... args) throws Exception {
return method.invokeChecked(null, args);
}
public R invoke(Object... args) {
return method.invoke(null, args);
}
}
public static class Builder {
private final String name;
private ClassLoader loader = Thread.currentThread().getContextClassLoader();
private UnboundMethod method = null;
public Builder(String methodName) {
this.name = methodName;
}
/**
* Set the {@link ClassLoader} used to lookup classes by name.
*
* If not set, the current thread's ClassLoader is used.
*
* @param loader a ClassLoader
* @return this Builder for method chaining
*/
public Builder loader(ClassLoader loader) {
this.loader = loader;
return this;
}
/**
* If no implementation has been found, adds a NOOP method.
*
* Note: calls to impl will not match after this method is called!
*
* @return this Builder for method chaining
*/
public Builder defaultNoop() {
if (method == null) {
this.method = UnboundMethod.NOOP;
}
return this;
}
/**
* Checks for an implementation, first finding the given class by name.
*
* @param className name of a class
* @param methodName name of a method (different from constructor)
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder impl(String className, String methodName, Class... argClasses) {
// don't do any work if an implementation has been found
if (method != null) {
return this;
}
try {
Class targetClass = Class.forName(className, true, loader);
impl(targetClass, methodName, argClasses);
} catch (ClassNotFoundException e) {
// not the right implementation
}
return this;
}
/**
* Checks for an implementation, first finding the given class by name.
*
* The name passed to the constructor is the method name used.
*
* @param className name of a class
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder impl(String className, Class... argClasses) {
impl(className, name, argClasses);
return this;
}
/**
* Checks for a method implementation.
*
* @param methodName name of a method (different from constructor)
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder impl(Class targetClass, String methodName, Class... argClasses) {
// don't do any work if an implementation has been found
if (method != null) {
return this;
}
try {
this.method = new UnboundMethod(
targetClass.getMethod(methodName, argClasses), name);
} catch (NoSuchMethodException e) {
// not the right implementation
}
return this;
}
/**
* Checks for a method implementation.
*
* The name passed to the constructor is the method name used.
*
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder impl(Class targetClass, Class... argClasses) {
impl(targetClass, name, argClasses);
return this;
}
public Builder ctorImpl(Class targetClass, Class... argClasses) {
// don't do any work if an implementation has been found
if (method != null) {
return this;
}
try {
this.method = new DynConstructors.Builder()
.impl(targetClass, argClasses)
.buildChecked();
} catch (NoSuchMethodException e) {
// not the right implementation
}
return this;
}
public Builder ctorImpl(String className, Class... argClasses) {
// don't do any work if an implementation has been found
if (method != null) {
return this;
}
try {
this.method = new DynConstructors.Builder()
.impl(className, argClasses)
.buildChecked();
} catch (NoSuchMethodException e) {
// not the right implementation
}
return this;
}
/**
* Checks for an implementation, first finding the given class by name.
*
* @param className name of a class
* @param methodName name of a method (different from constructor)
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder hiddenImpl(String className, String methodName, Class... argClasses) {
// don't do any work if an implementation has been found
if (method != null) {
return this;
}
try {
Class targetClass = Class.forName(className, true, loader);
hiddenImpl(targetClass, methodName, argClasses);
} catch (ClassNotFoundException e) {
// not the right implementation
}
return this;
}
/**
* Checks for an implementation, first finding the given class by name.
*
* The name passed to the constructor is the method name used.
*
* @param className name of a class
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder hiddenImpl(String className, Class... argClasses) {
hiddenImpl(className, name, argClasses);
return this;
}
/**
* Checks for a method implementation.
*
* @param methodName name of a method (different from constructor)
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder hiddenImpl(Class targetClass, String methodName, Class... argClasses) {
// don't do any work if an implementation has been found
if (method != null) {
return this;
}
try {
Method hidden = targetClass.getDeclaredMethod(methodName, argClasses);
AccessController.doPrivileged(new MakeAccessible(hidden));
this.method = new UnboundMethod(hidden, name);
} catch (SecurityException e) {
// unusable
} catch (NoSuchMethodException e) {
// not the right implementation
}
return this;
}
/**
* Checks for a method implementation.
*
* The name passed to the constructor is the method name used.
*
* @param argClasses argument classes for the method
* @return this Builder for method chaining
* @see {@link java.lang.Class#forName(String)}
* @see {@link java.lang.Class#getMethod(String, Class[])}
*/
public Builder hiddenImpl(Class targetClass, Class... argClasses) {
hiddenImpl(targetClass, name, argClasses);
return this;
}
/**
* Returns the first valid implementation as a UnboundMethod or throws a
* NoSuchMethodException if there is none.
*
* @return a {@link UnboundMethod} with a valid implementation
* @throws NoSuchMethodException if no implementation was found
*/
public UnboundMethod buildChecked() throws NoSuchMethodException {
if (method != null) {
return method;
} else {
throw new NoSuchMethodException("Cannot find method: " + name);
}
}
/**
* Returns the first valid implementation as a UnboundMethod or throws a
* RuntimeError if there is none.
*
* @return a {@link UnboundMethod} with a valid implementation
* @throws RuntimeException if no implementation was found
*/
public UnboundMethod build() {
if (method != null) {
return method;
} else {
throw new RuntimeException("Cannot find method: " + name);
}
}
/**
* Returns the first valid implementation as a BoundMethod or throws a
* NoSuchMethodException if there is none.
*
* @param receiver an Object to receive the method invocation
* @return a {@link BoundMethod} with a valid implementation and receiver
* @throws IllegalStateException if the method is static
* @throws IllegalArgumentException if the receiver's class is incompatible
* @throws NoSuchMethodException if no implementation was found
*/
public BoundMethod buildChecked(Object receiver) throws NoSuchMethodException {
return buildChecked().bind(receiver);
}
/**
* Returns the first valid implementation as a BoundMethod or throws a
* RuntimeError if there is none.
*
* @param receiver an Object to receive the method invocation
* @return a {@link BoundMethod} with a valid implementation and receiver
* @throws IllegalStateException if the method is static
* @throws IllegalArgumentException if the receiver's class is incompatible
* @throws RuntimeException if no implementation was found
*/
public BoundMethod build(Object receiver) {
return build().bind(receiver);
}
/**
* Returns the first valid implementation as a StaticMethod or throws a
* NoSuchMethodException if there is none.
*
* @return a {@link StaticMethod} with a valid implementation
* @throws IllegalStateException if the method is not static
* @throws NoSuchMethodException if no implementation was found
*/
public StaticMethod buildStaticChecked() throws NoSuchMethodException {
return buildChecked().asStatic();
}
/**
* Returns the first valid implementation as a StaticMethod or throws a
* RuntimeException if there is none.
*
* @return a {@link StaticMethod} with a valid implementation
* @throws IllegalStateException if the method is not static
* @throws RuntimeException if no implementation was found
*/
public StaticMethod buildStatic() {
return build().asStatic();
}
}
private static class MakeAccessible implements PrivilegedAction {
private Method hidden;
public MakeAccessible(Method hidden) {
this.hidden = hidden;
}
@Override
public Void run() {
hidden.setAccessible(true);
return null;
}
}
}