Try to get the initial value of a static field - Java Reflection

Java examples for Reflection:Field Value

  1. HOME
  2. Java
  3. Reflection
  4. Field Value

Description

Try to get the initial value of a static field

Demo Code

/*/*from ww w  . ja  va2  s.  c o m*/
 * 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.
 */
//package com.java2s;
import java.lang.reflect.Array;
import java.lang.reflect.Field;

public class Main {
    public static void main(String[] argv) throws Exception {
        Class clazz = String.class;
        String fieldName = "java2s.com";
        System.out.println(java.util.Arrays
                .toString(getInitializationExpression(clazz, fieldName)));
    }

    public static ClassLoader classLoader;

    /**
     * Try to get the initial value of a static field
     * @param clazz     The class.
     * @param fieldName The name of the field.
     * @return The initial value or null.
     */
    public static String[] getInitializationExpression(Class<?> clazz,
            String fieldName) {
        try {
            final Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            final Object value = field.get(null);
            if (value != null) {
                if (value.getClass().isArray()) {
                    final String[] values = new String[Array
                            .getLength(value)];
                    for (int i = 0; i < values.length; i++) {
                        values[i] = Array.get(value, i).toString();
                    }
                    return values;
                }
                return new String[] { value.toString() };
            }
            return null;
        } catch (NoClassDefFoundError e) {
            // ignore and just return null
        } catch (Exception e) {
            // ignore and just return null
        }
        return null;
    }

    /**
     * Get the compiled class.
     */
    public static Class<?> getClass(String name) {
        if (classLoader == null) {
            return null;
        }
        try {
            if (name.endsWith(".class")) {
                name = name.substring(0, name.length() - 6);
            }
            return classLoader.loadClass(name);
        } catch (ClassNotFoundException e) {
            return null;
        }
    }
}

Related Tutorials