Java Reflection Field Value Set setFieldValue(Class clazz, String fieldName, Object value)

Description

set Field Value

License

Open Source License

Declaration

public static void setFieldValue(Class<?> clazz, String fieldName, Object value) 

Method Source Code

//package com.java2s;
/**/*from w w  w.  j  a  v  a  2s.c om*/
 * Helios, OpenSource Monitoring
 * Brought to you by the Helios Development Group
 *
 * Copyright 2014, Helios Development Group and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 
 *
 */

import java.lang.reflect.Field;

import java.lang.reflect.Modifier;

public class Main {
    public static void setFieldValue(Class<?> clazz, String fieldName, Object value) {
        setFieldValue(clazz, null, fieldName, value);
    }

    public static void setFieldValue(Class<?> clazz, Object target, String fieldName, Object value) {
        try {
            Field targetField = clazz.getDeclaredField(fieldName);
            boolean modifiedAccess = false;
            boolean modifiedWriteability = false;
            try {
                if (!targetField.isAccessible()) {
                    targetField.setAccessible(true);
                    modifiedAccess = true;
                }
                if (Modifier.isFinal(targetField.getModifiers())) {
                    targetField = setFieldEditable(clazz, fieldName);
                    modifiedWriteability = true;
                }
                if (targetField.getType().isPrimitive()) {
                    setFieldPrimitive(target, targetField, value);
                } else {
                    targetField.set(target, value);
                }
            } finally {
                if (modifiedAccess)
                    targetField.setAccessible(false);
                if (modifiedWriteability)
                    setFieldReadOnly(clazz, fieldName);
            }
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    /**
     * Sets a field in a class to be modifiable regardless of finality or privacy
     * @param clazz The class to modify
     * @param fieldName The name of the field to modify
     * @return the modified field
     */
    public static Field setFieldEditable(Class<?> clazz, String fieldName) {
        try {
            Field targetField = clazz.getDeclaredField(fieldName);
            Field modifierField = Field.class.getDeclaredField("modifiers");
            targetField.setAccessible(true);
            modifierField.setAccessible(true);
            modifierField.setInt(targetField, targetField.getModifiers() & ~Modifier.FINAL);
            return targetField;
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    public static void setFieldPrimitive(Object target, Field field, Object value) {
        try {
            final Class<?> c = field.getType();
            if (c == boolean.class) {
                field.setBoolean(target, (Boolean) value);
            } else if (c == byte.class) {
                field.setByte(target, ((Number) value).byteValue());
            } else if (c == char.class) {
                field.setChar(target, (Character) value);
            } else if (c == short.class) {
                field.setShort(target, ((Number) value).shortValue());
            } else if (c == int.class) {
                field.setInt(target, ((Number) value).intValue());
            } else if (c == float.class) {
                field.setFloat(target, ((Number) value).floatValue());
            } else if (c == long.class) {
                field.setLong(target, ((Number) value).longValue());
            } else if (c == double.class) {
                field.setDouble(target, ((Number) value).doubleValue());
            } else {
                throw new RuntimeException("WTF ? --->  [" + c.getName() + "]");
            }
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }

    }

    /**
     * Reverses the changes made in {@link #setFieldEditable(Class, String)}
     * @param clazz The class to modify
     * @param fieldName The name of the field to modify
     */
    public static void setFieldReadOnly(Class<?> clazz, String fieldName) {
        try {
            Field targetField = clazz.getDeclaredField(fieldName);
            Field modifierField = Field.class.getDeclaredField("modifiers");
            targetField.setAccessible(true);
            modifierField.setAccessible(true);
            modifierField.setInt(targetField, targetField.getModifiers() | Modifier.FINAL);
            modifierField.setAccessible(false);
            targetField.setAccessible(false);
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }
}

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2. setFieldValue(Class clazz, Object instance, String fieldName, T value)
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