net.sf.derquinsej.Methods.java Source code

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/*
 * Copyright 2008 the original author or authors.
 *
 * 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 net.sf.derquinsej;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;

import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;

/**
 * Utility methods for Methods.
 * @author Andres Rodriguez
 */
public final class Methods {
    /**
     * Not instantiable.
     */
    private Methods() {
        throw new AssertionError();
    }

    /**
     * Returns the methods of a class as an iterable.
     * @param klass Class to process.
     * @return The methods of the class.
     * @throws NullPointerException if the argument is null.
     */
    public static List<Method> getMethods(Class<?> klass) {
        Preconditions.checkNotNull(klass, "A class must be provided");
        return Arrays.asList(klass.getMethods());
    }

    public static Predicate<Method> withParameters(final int numParameters) {
        final Predicate<Method> predicate = new Predicate<Method>() {
            public boolean apply(Method input) {
                return input.getParameterTypes().length == numParameters;
            }
        };
        return predicate;
    }

    public static Predicate<Method> withParameterOfType(final int index, final Class<?> type) {
        final Predicate<Method> predicate = new Predicate<Method>() {
            public boolean apply(Method input) {
                return input.getParameterTypes()[index].equals(type);
            }
        };
        return predicate;
    }

    public static Predicate<Method> withParameterTypeAssignableTo(final int index, final Class<?> type) {
        final Predicate<Method> predicate = new Predicate<Method>() {
            public boolean apply(Method input) {
                return type.isAssignableFrom(input.getParameterTypes()[index]);
            }
        };
        return predicate;
    }

    public static Predicate<Method> withReturnTypeAssignableTo(final int index, final Class<?> type) {
        final Predicate<Method> predicate = new Predicate<Method>() {
            public boolean apply(Method input) {
                return type.isAssignableFrom(input.getReturnType());
            }
        };
        return predicate;
    }

    public static Predicate<Method> annotated(final Class<? extends Annotation> annotation) {
        final Predicate<Method> predicate = new Predicate<Method>() {
            public boolean apply(Method input) {
                return input.isAnnotationPresent(annotation);
            }
        };
        return predicate;
    }

    private static final Function<Method, Class<?>> RETURN_TYPE = new Function<Method, Class<?>>() {
        public Class<?> apply(Method input) {
            return input.getReturnType();
        };
    };

    public static Function<Method, Class<?>> returnType() {
        return RETURN_TYPE;
    }

    public static Function<Method, Class<?>> parameterType(final int parameter) {
        return new Function<Method, Class<?>>() {
            public Class<?> apply(Method input) {
                return input.getParameterTypes()[parameter];
            };
        };
    }

}