使用struts2的json插件时，自己定义日期格式经常使用的方式是在get属性上加入@JSON注解，这个对于少量Date属性还能够，可是假设date字段多了，总不可能去给每一个date get方法加入json注解吧！

发现极大不便后查看了sturts-plugin.xml 中的json-default定义，源代码跟踪到json拦截器内部一点发现都没有，自己定义

org.apache.struts2.json.JSONPopulator中的dateFormatter属性全然不起效果。可是在同一个包下：org.apache.struts2.json 发现了类：JSONWriter 在这里才找到了一些端倪

将源代码中的

 
    /**
     * Add date to buffer
     */
    protected void date(Date date, Method method) {
        JSON json = null;
        if (method != null)
            json = method.getAnnotation(JSON.class);
        if (this.formatter == null)
            this.formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        
        DateFormat formatter = (json != null) && (json.format().length() > 0) ? new SimpleDateFormat(json
                .format()) : this.formatter;
        this.string(formatter.format(date));
    }

SimpleDateFormat 格式改成自己定义日期格式就可以，这样全局json 日期格式就自己定义完毕了！

注意：覆盖时仅仅须要自己定义包：org.apache.struts2.json将改动后的<span style="font-family: Arial, Helvetica, sans-serif;">JSONWriter放到包下就可以，没有必要去改动插件中的源代码信息 </span>

以下附上整个类的源代码：

/*
 * $Id$
 *
 * 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 org.apache.struts2.json;

import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import org.apache.struts2.json.annotations.JSON;
import org.apache.struts2.json.annotations.JSONFieldBridge;
import org.apache.struts2.json.annotations.JSONParameter;
import org.apache.struts2.json.bridge.FieldBridge;
import org.apache.struts2.json.bridge.ParameterizedBridge;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.text.CharacterIterator;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.StringCharacterIterator;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.regex.Pattern;

/**
 * <p>
 * Serializes an object into JavaScript Object Notation (JSON). If cyclic
 * references are detected they will be nulled out.
 * </p>
 */
public class JSONWriter {

    private static final Logger LOG = LoggerFactory.getLogger(JSONWriter.class);

    /**
     * By default, enums are serialised as name=value pairs
     */
    public static final boolean ENUM_AS_BEAN_DEFAULT = false;

    private static char[] hex = "0123456789ABCDEF".toCharArray();

    private static final ConcurrentMap<Class<?>, BeanInfo> BEAN_INFO_CACHE_IGNORE_HIERARCHY = new ConcurrentHashMap<Class<?>, BeanInfo>();
    private static final ConcurrentMap<Class<?>, BeanInfo> BEAN_INFO_CACHE = new ConcurrentHashMap<Class<?>, BeanInfo>();

    private StringBuilder buf = new StringBuilder();
    private Stack<Object> stack = new Stack<Object>();
    private boolean ignoreHierarchy = true;
    private Object root;
    private boolean buildExpr = true;
    private String exprStack = "";
    private Collection<Pattern> excludeProperties;
    private Collection<Pattern> includeProperties;
    private DateFormat formatter;
    private boolean enumAsBean = ENUM_AS_BEAN_DEFAULT;
    private boolean excludeNullProperties;

    /**
     * @param object Object to be serialized into JSON
     * @return JSON string for object
     * @throws JSONException
     */
    public String write(Object object) throws JSONException {
        return this.write(object, null, null, false);
    }

    /**
     * @param object Object to be serialized into JSON
     * @return JSON string for object
     * @throws JSONException
     */
    public String write(Object object, Collection<Pattern> excludeProperties,
                        Collection<Pattern> includeProperties, boolean excludeNullProperties) throws JSONException {
        this.excludeNullProperties = excludeNullProperties;
        this.buf.setLength(0);
        this.root = object;
        this.exprStack = "";
        this.buildExpr = ((excludeProperties != null) && !excludeProperties.isEmpty())
                || ((includeProperties != null) && !includeProperties.isEmpty());
        this.excludeProperties = excludeProperties;
        this.includeProperties = includeProperties;
        this.value(object, null);

        return this.buf.toString();
    }

    /**
     * Detect cyclic references
     */
    protected void value(Object object, Method method) throws JSONException {
        if (object == null) {
            this.add("null");

            return;
        }

        if (this.stack.contains(object)) {
            Class clazz = object.getClass();

            // cyclic reference
            if (clazz.isPrimitive() || clazz.equals(String.class)) {
                this.process(object, method);
            } else {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Cyclic reference detected on " + object);
                }

                this.add("null");
            }

            return;
        }

        this.process(object, method);
    }

    /**
     * Serialize object into json
     */
    protected void process(Object object, Method method) throws JSONException {
        this.stack.push(object);

        if (object instanceof Class) {
            this.string(object);
        } else if (object instanceof Boolean) {
            this.bool((Boolean) object);
        } else if (object instanceof Number) {
            this.add(object);
        } else if (object instanceof String) {
            this.string(object);
        } else if (object instanceof Character) {
            this.string(object);
        } else if (object instanceof Map) {
            this.map((Map) object, method);
        } else if (object.getClass().isArray()) {
            this.array(object, method);
        } else if (object instanceof Iterable) {
            this.array(((Iterable) object).iterator(), method);
        } else if (object instanceof Date) {
            this.date((Date) object, method);
        } else if (object instanceof Calendar) {
            this.date(((Calendar) object).getTime(), method);
        } else if (object instanceof Locale) {
            this.string(object);
        } else if (object instanceof Enum) {
            this.enumeration((Enum) object);
        } else {
            processCustom(object, method);
        }

        this.stack.pop();
    }

    /**
     * Serialize custom object into json
     */
    protected void processCustom(Object object, Method method) throws JSONException {
        this.bean(object);
    }

    /**
     * Instrospect bean and serialize its properties
     */
    protected void bean(Object object) throws JSONException {
        this.add("{");

        BeanInfo info;

        try {
            Class clazz = object.getClass();

            info = ((object == this.root) && this.ignoreHierarchy)
                    ? getBeanInfoIgnoreHierarchy(clazz)
                    : getBeanInfo(clazz);

            PropertyDescriptor[] props = info.getPropertyDescriptors();

            boolean hasData = http://www.mamicode.com/false;>