Java Method Call invoke(Object obj, String method, Object param, Object paramType)

Description

Invoke a method if it can be found!

License

Apache License

Parameter

Parameter	Description
obj	the object upon which, to call the method
method	the method you would like to call
param	the parameter (or parameters if you pass an array) you wish to pass. The types of the parameters form part of the method signature so make sure types are right.

Return

the return value from the method - if there is one. This will be null if the method was not avaialble and also null if the method does not have a return value.

Declaration

public static Object invoke(Object obj, String method, Object param, Object paramType) 

Method Source Code

//package com.java2s;
/*// www .  j  a va 2s .  c o  m
 *  Copyright 2006 The National Library of New Zealand
 *
 *  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.
 */

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Main {
    /**
     * Invoke a method if it can be found! Use this to remain backward
     * compatible with older JDK libraries that do not have the methods you
     * might want. This will allow your code to compile and run - as long as you
     * have a plan for what to do if this method returns null.
     * 
     * @param obj
     *            the object upon which, to call the method
     * @param method
     *            the method you would like to call
     * @param param
     *            the parameter (or parameters if you pass an array) you wish to
     *            pass. The types of the parameters form part of the method
     *            signature so make sure types are right.
     * @return the return value from the method - if there is one. This will be
     *         null if the method was not avaialble and also null if the method
     *         does not have a return value.
     */
    public static Object invoke(Object obj, String method, Object param, Object paramType) {
        Object result = null;
        Object[] params = null;
        Class[] paramTypes = null;
        if (param.getClass().isArray()) {
            params = (Object[]) param;
            paramTypes = (Class[]) paramType;
        } else {
            params = new Object[1];
            params[0] = param;
            paramTypes = new Class[1];
            paramTypes[0] = (Class) paramType;
        }
        try {
            Method realMethod = obj.getClass().getMethod(method, paramTypes);
            realMethod.setAccessible(true);
            result = realMethod.invoke(obj, params);

            // sucessful invoke, if the result is still null, then the method
            // did not have a return value
        } catch (IllegalAccessException ex) {
            // just can't call it - bad luck. The desired behaviour is to
            // continue without throwing exceptions
            // modify this to send back an error
        } catch (InvocationTargetException ex) {
            // just can't call it - bad luck. The desired behaviour is to
            // continue without throwing exceptions
            // modify this to send back an error
        } catch (NoSuchMethodException ex) {
            // just can't call it - bad luck. The desired behaviour is to
            // continue without throwing exceptions
            // modify this to send back an error
        }

        return result;
    }
}

Related

1. invoke(Object o, String name, Object[] args)
2. invoke(Object obj, Method method, Object[] args)
3. invoke(Object obj, Method method, Object[] params)
4. invoke(Object obj, String method, Class[] params, Object[] args)
5. invoke(Object obj, String method, Class[] params, Object[] args)
6. invoke(Object obj, String methodName)
7. invoke(Object obj, String methodName, boolean newValue)
8. invoke(Object obj, String methodName, Class argType, Object arg)
9. invoke(Object obj, String methodName, Class clazz, Object newValue)