Java Reflection Field Set setField(Object o, String fieldName, Object value)

Description

Sets the value of a field on an object

License

Open Source License

Parameter

Parameter	Description
o	The object that contains the field
fieldName	The name of the field
value	The new value

Return

The previous value of the field

Declaration

public static Object setField(Object o, String fieldName, Object value) 

Method Source Code

//package com.java2s;
/*//from  w  w  w.  j av a2  s  .  c om
 *
 *  Copyright 2016,2017 DTCC, Fujitsu Australia Software Technology, IBM - All Rights Reserved.
 *
 *  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.Field;

public class Main {
    /**
     * Sets the value of a field on an object
     *
     * @param o         The object that contains the field
     * @param fieldName The name of the field
     * @param value     The new value
     * @return The previous value of the field
     */
    public static Object setField(Object o, String fieldName, Object value) {
        Object oldVal = null;
        try {
            final Field field = getFieldInt(o.getClass(), fieldName);
            field.setAccessible(true);
            oldVal = field.get(o);
            field.set(o, value);
        } catch (Exception e) {
            throw new RuntimeException("Cannot get value of field " + fieldName, e);
        }
        return oldVal;
    }

    private static Field getFieldInt(Class o, String name) throws NoSuchFieldException {
        Field ret;
        try {
            ret = o.getDeclaredField(name);
        } catch (NoSuchFieldException e) {

            Class superclass = o.getSuperclass();
            if (null != superclass) {
                ret = getFieldInt(superclass, name);

            } else {
                throw e;
            }

        }
        ret.setAccessible(true);
        return ret;
    }
}

Related

1. setField(Object instance, String name, Object obj)
2. setField(Object instance, String sField, Object value)
3. setField(Object item, Field f, Object value)
4. setField(Object o, String fieldName, Object inject)
5. setField(Object o, String fieldName, Object value)
6. setField(Object o, String name, Object value)
7. setField(Object obj, Class fieldOwner, String fieldName, Object value)
8. setField(Object obj, Field field, Object value)
9. setField(Object obj, Object value, String fieldName)