groovy-core/src/main/org/codehaus/groovy/runtime/NewInstanceMetaMethod.java

/*
 * Copyright 2003-2007 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 org.codehaus.groovy.runtime;

import groovy.lang.MetaMethod;

import java.lang.reflect.Modifier;

import org.codehaus.groovy.reflection.ParameterTypes;
import org.codehaus.groovy.reflection.CachedClass;

/**
 * A MetaMethod implementation where the underlying method is really a static
 * helper method on some class but it appears to be an instance method on a class.
 *
 * This implementation is used to add new methods to the JDK writing them as normal
 * static methods with the first parameter being the class on which the method is added.
 *
 * @author <a href="mailto:james@coredevelopers.net">James Strachan</a>
 * @version $Revision$
 */
public class NewInstanceMetaMethod extends MetaMethod {

    private static final Class[] EMPTY_TYPE_ARRAY = {};

    private MetaMethod metaMethod;
    private Class[] bytecodeParameterTypes ;


    public NewInstanceMetaMethod(MetaMethod metaMethod) {
        super(metaMethod);
        this.metaMethod = metaMethod;
        init();
    }

    public NewInstanceMetaMethod(String name, Class declaringClass, CachedClass[] parameterTypes, Class returnType, int modifiers) {
        super(name, declaringClass, parameterTypes, returnType, modifiers);
        this.metaMethod = new MetaMethod(name, declaringClass, parameterTypes,returnType, modifiers);
        init();
    }

    private void init() {
        bytecodeParameterTypes = metaMethod.getNativeParameterTypes();
        int size = bytecodeParameterTypes !=null ? bytecodeParameterTypes.length : 0;
        Class[] logicalParameterTypes;
        if (size <= 1) {
            logicalParameterTypes = EMPTY_TYPE_ARRAY;
        } else {
            logicalParameterTypes = new Class[--size];
            System.arraycopy(bytecodeParameterTypes, 1, logicalParameterTypes, 0, size);
        }
        paramTypes = new ParameterTypes(logicalParameterTypes);
    }

    public Class getDeclaringClass() {
        return getBytecodeParameterTypes()[0];
    }

    public boolean isStatic() {
        return false;
    }

    public int getModifiers() {
        // lets clear the static bit
        return super.getModifiers() ^ Modifier.STATIC;
    }

    public Class[] getBytecodeParameterTypes() {
        return bytecodeParameterTypes;
    }

    public Object invoke(Object object, Object[] arguments)  {
        // we need to cheat using the type
        int size = arguments.length;
        Object[] newArguments = new Object[size + 1];
        newArguments[0] = object;
        System.arraycopy(arguments, 0, newArguments, 1, size);
        return metaMethod.invoke(null, newArguments);
    }

    public Class getOwnerClass() {
        return getBytecodeParameterTypes()[0];
    }
}