Java Reflection Field Value Set setFieldValue(final Field field, final Object instance, final Object value)

Description

Sets the value of a Field , making it accessible if required.

License

Apache License

Parameter

Parameter	Description
field	the Field to write a value to (must not be null ).
instance	the instance to write the value to or null only if the field is static.
value	the (possibly wrapped) value to write to the field.

Exception

Parameter	Description
NullPointerException	if field is null, or if instance is null but field is not static.

Declaration

public static void setFieldValue(final Field field, final Object instance, final Object value) 

Method Source Code

//package com.java2s;
/*//w ww .j  a  v  a2  s . c  om
 * 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.
 */

import java.lang.reflect.AccessibleObject;

import java.lang.reflect.Field;

import java.lang.reflect.Member;
import java.lang.reflect.Modifier;
import java.util.Objects;

public class Main {
    /**
     * Sets the value of a {@link Field}, making it accessible if required.
     *
     * @param field    the Field to write a value to (must not be {@code null}).
     * @param instance the instance to write the value to or {@code null} only if the field is static.
     * @param value    the (possibly wrapped) value to write to the field.
     * @throws NullPointerException if {@code field} is {@code null}, or if {@code instance} is {@code null} but
     *                              {@code field} is not {@code static}.
     * @see Field#set(Object, Object)
     */
    public static void setFieldValue(final Field field, final Object instance, final Object value) {
        makeAccessible(field);
        if (!Modifier.isStatic(field.getModifiers())) {
            Objects.requireNonNull(instance, "No instance given for non-static field");
        }
        try {
            field.set(instance, value);
        } catch (final IllegalAccessException e) {
            throw new UnsupportedOperationException(e);
        }
    }

    /**
     * Makes a {@link Member} {@link AccessibleObject#isAccessible() accessible} if the member is not public.
     *
     * @param <T> type of the object to make accessible
     * @param member the Member to make accessible (must not be {@code null}).
     * @throws NullPointerException if {@code member} is {@code null}.
     */
    public static <T extends AccessibleObject & Member> void makeAccessible(final T member) {
        if (!isAccessible(member) && !member.isAccessible()) {
            member.setAccessible(true);
        }
    }

    /**
     * Makes a {@link Field} {@link AccessibleObject#isAccessible() accessible} if it is not public or if it is final.
     *
     * <p>Note that using this method to make a {@code final} field writable will most likely not work very well due to
     * compiler optimizations and the like.</p>
     *
     * @param field the Field to make accessible (must not be {@code null}).
     * @throws NullPointerException if {@code field} is {@code null}.
     */
    public static void makeAccessible(final Field field) {
        Objects.requireNonNull(field, "No field provided");
        if ((!isAccessible(field) || Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) {
            field.setAccessible(true);
        }
    }

    /**
     * Indicates whether or not a {@link Member} is both public and is contained in a public class.
     *
     * @param <T> type of the object whose accessibility to test
     * @param member the Member to check for public accessibility (must not be {@code null}).
     * @return {@code true} if {@code member} is public and contained in a public class.
     * @throws NullPointerException if {@code member} is {@code null}.
     */
    public static <T extends AccessibleObject & Member> boolean isAccessible(final T member) {
        Objects.requireNonNull(member, "No member provided");
        return Modifier.isPublic(member.getModifiers())
                && Modifier.isPublic(member.getDeclaringClass().getModifiers());
    }
}

Related

1. setFieldValue(Field field, Object object, Object value)
2. setFieldValue(Field field, Object target, Object value)
3. setFieldValue(Field field, Object value, Object instance)
4. setFieldValue(Field field, Object value, Object target)
5. setFieldValue(final Class clazz, final String fieldName, final Object fieldValue)
6. setFieldValue(final Field field, final Object obj, final Object value)
7. setFieldValue(final Field field, final Object value, final Object object)
8. setFieldValue(final Object bean, final Field field, final Object value)
9. setFieldValue(final Object obj, final String fieldName, final Object value)