ReflectUtil.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.tools.ant.util;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.function.Predicate;
import java.util.stream.Stream;
import org.apache.tools.ant.BuildException;
/**
* Utility class to handle reflection on java objects.
* The class contains static methods to call reflection
* methods, catch any exceptions, converting them
* to BuildExceptions.
*/
// CheckStyle:FinalClassCheck OFF - backward compatible
public class ReflectUtil {
/** private constructor */
private ReflectUtil() {
}
/**
* Create an instance of a class using the constructor matching
* the given arguments.
* @param <T> desired type
* @param ofClass Class<T>
* @param argTypes Class<?>[]
* @param args Object[]
* @return class instance
* @since Ant 1.8.0
*/
public static <T> T newInstance(Class<T> ofClass,
Class<?>[] argTypes,
Object[] args) {
try {
Constructor<T> con = ofClass.getConstructor(argTypes);
return con.newInstance(args);
} catch (Exception t) {
throwBuildException(t);
return null; // NotReached
}
}
/**
* Call a method on the object with no parameters.
* @param <T> desired type
* @param obj the object to invoke the method on.
* @param methodName the name of the method to call
* @return the object returned by the method
*/
@SuppressWarnings("unchecked")
public static <T> T invoke(Object obj, String methodName) {
try {
Method method = obj.getClass().getMethod(methodName);
return (T) method.invoke(obj);
} catch (Exception t) {
throwBuildException(t);
return null; // NotReached
}
}
/**
* Call a method on the object with no parameters.
* Note: Unlike the invoke method above, this
* calls class or static methods, not instance methods.
* @param <T> desired type
* @param obj the object to invoke the method on.
* @param methodName the name of the method to call
* @return the object returned by the method
*/
@SuppressWarnings("unchecked")
public static <T> T invokeStatic(Object obj, String methodName) {
try {
Method method = ((Class<?>) obj).getMethod(methodName);
return (T) method.invoke(obj);
} catch (Exception t) {
throwBuildException(t);
return null; // NotReached
}
}
/**
* Call a method on the object with one argument.
* @param <T> desired type
* @param obj the object to invoke the method on.
* @param methodName the name of the method to call
* @param argType the type of argument.
* @param arg the value of the argument.
* @return the object returned by the method
*/
@SuppressWarnings("unchecked")
public static <T> T invoke(
Object obj, String methodName, Class<?> argType, Object arg) {
try {
Method method = obj.getClass().getMethod(methodName, argType);
return (T) method.invoke(obj, arg);
} catch (Exception t) {
throwBuildException(t);
return null; // NotReached
}
}
/**
* Call a method on the object with two argument.
* @param <T> desired type
* @param obj the object to invoke the method on.
* @param methodName the name of the method to call
* @param argType1 the type of the first argument.
* @param arg1 the value of the first argument.
* @param argType2 the type of the second argument.
* @param arg2 the value of the second argument.
* @return the object returned by the method
*/
@SuppressWarnings("unchecked")
public static <T> T invoke(
Object obj, String methodName, Class<?> argType1, Object arg1,
Class<?> argType2, Object arg2) {
try {
Method method =
obj.getClass().getMethod(methodName, argType1, argType2);
return (T) method.invoke(obj, arg1, arg2);
} catch (Exception t) {
throwBuildException(t);
return null; // NotReached
}
}
/**
* Get the value of a field in an object.
* @param <T> desired type
* @param obj the object to look at.
* @param fieldName the name of the field in the object.
* @return the value of the field.
* @throws BuildException if there is an error.
*/
@SuppressWarnings("unchecked")
public static <T> T getField(Object obj, String fieldName)
throws BuildException {
try {
Field field = obj.getClass().getDeclaredField(fieldName);
field.setAccessible(true);
return (T) field.get(obj);
} catch (Exception t) {
throwBuildException(t);
return null; // NotReached
}
}
/**
* A method to convert an invocationTargetException to
* a buildexception and throw it.
* @param t the invocation target exception.
* @throws BuildException the converted exception.
*/
public static void throwBuildException(Exception t)
throws BuildException {
throw toBuildException(t);
}
/**
* A method to convert an invocationTargetException to
* a buildexception.
* @param t the invocation target exception.
* @return the converted exception.
* @since ant 1.7.1
*/
public static BuildException toBuildException(Exception t) {
if (t instanceof InvocationTargetException) {
Throwable t2 = ((InvocationTargetException) t)
.getTargetException();
if (t2 instanceof BuildException) {
return (BuildException) t2;
}
return new BuildException(t2);
}
return new BuildException(t);
}
/**
* A method to test if an object responds to a given
* message (method call)
* @param o the object
* @param methodName the method to check for
* @return true if the object has the method.
* @throws BuildException if there is a problem.
*/
public static boolean respondsTo(Object o, String methodName)
throws BuildException {
try {
return Stream.of(o.getClass().getMethods()).map(Method::getName)
.anyMatch(Predicate.isEqual(methodName));
} catch (Exception t) {
throw toBuildException(t);
}
}
}