java与json互相转换(解决日期问题)

JSON 即 JavaScript Object Natation，它是一种轻量级的数据交换格式，非常适合于服务器与 JavaScript 的交互。本文主要讲解下java和JSON之间的转换，特别是解决互相转换遇到日期问题的情况。
    一、需要相关的jar包：
    json-lib-xxx.jar
    ezmorph-xxx.jar
    commons-httpclient-xxx.jar
    commons-lang-xxx.jar
    commons-logging-xxx.jar
    commons-collections-xxx.jar
    上面的包可以从下面的连接下载：
    http://commons.apache.org/index.html
    http://json-lib.sourceforge.net
    http://ezmorph.sourceforge.net
   二、java-》JSON
     1.List-》JSON
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List<String> list = new ArrayList<String>();
list.add("apple");
list.add("orange");
JSONArray jarr = JSONArray.fromObject(list);
System.out.println("list->json:" + jarr.toString());

    打印结果：list->json:["apple","orange"]
     2.Map-》JSON

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Map<String, Object> map = new HashMap<String, Object>();
map.put("name", "Michael");
map.put("baby", new String[] { "Lucy", "Lily" });
map.put("age", 30);
JSONObject jo = JSONObject.fromObject(map);
System.out.println("map->json:" + jo.toString());

    打印结果：map->json:{"age":30,"name":"Michael","baby":["Lucy","Lily"]}
    3.bean->JSON

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JsonBean bean = new JsonBean();
bean.setName("NewBaby");
bean.setAge(1);
bean.setBorn(new Date());
jo = JSONObject.fromObject(bean);
System.out.println("bean->json:" + jo.toString());

打印结果：bean->json:{"age":1,"born":{"date":10,"day":3,"hours":14,"minutes":14,"month":2,"seconds":1,"time":1268201641228,"timezoneOffset":-480,"year":110},"name":"NewBaby"}
   这时你会发现它把bean对象里的util.Date这个类型的所有属性一一转换出来。在实际运用过程中，大多数情况下我们希望能转化为yyyy-MM-dd这种格式，下面就讲一讲如何实现：
   首先要写一个新的类JsonDateValueProcessor如下：

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/**
* JSON 日期格式处理（java转化为JSON）
* @author Michael sun
*/
public class JsonDateValueProcessor implements JsonValueProcessor {

    /**
     * datePattern
     */
    private String datePattern = "yyyy-MM-dd";

    /**
     * JsonDateValueProcessor
     */
    public JsonDateValueProcessor() {
        super();
    }

    /**
     * @param format
     */
    public JsonDateValueProcessor(String format) {
        super();
        this.datePattern = format;
    }

    /**
     * @param value
     * @param jsonConfig
     * @return Object
     */
    public Object processArrayValue(Object value, JsonConfig jsonConfig) {
        return process(value);
    }

    /**
     * @param key
     * @param value
     * @param jsonConfig
     * @return Object
     */
    public Object processObjectValue(String key, Object value,
            JsonConfig jsonConfig) {
        return process(value);
    }

    /**
     * process
     * @param value
     * @return
     */
    private Object process(Object value) {
        try {
            if (value instanceof Date) {
                SimpleDateFormat sdf = new SimpleDateFormat(datePattern,
                        Locale.UK);
                return sdf.format((Date) value);
            }
            return value == null ? "" : value.toString();
        } catch (Exception e) {
            return "";
        }

    }

    /**
     * @return the datePattern
     */
    public String getDatePattern() {
        return datePattern;
    }

    /**
     * @param pDatePattern the datePattern to set
     */
    public void setDatePattern(String pDatePattern) {
        datePattern = pDatePattern;
    }

}

测试代码：

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JsonBean bean = new JsonBean();
bean.setName("NewBaby");
bean.setAge(1);
bean.setBorn(new Date());

JsonConfig jsonConfig = new JsonConfig();
jsonConfig.registerJsonValueProcessor(Date.class,new JsonDateValueProcessor());

JSONObject jo = JSONObject.fromObject(bean, jsonConfig);
System.out.println("bean->json:" + jo.toString());

打印结果：bean->json:{"age":1,"born":"2010-03-10","name":"NewBaby"}
这就能得到我们想要的结果了。

三、JSON-》java
1.如何把json的yyyy-MM-dd的转换为Bean中的util.Date类型：
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JSONUtils.getMorpherRegistry().registerMorpher(
          new DateMorpher(new String[] { "yyyy-MM-dd" }));

String jsonStr = "[{"name": "husband", "age": "26", "born": "1984-01-12"},{"name": "wife", "age": "20", "born": "1990-05-01"}]";

Collection<JsonBean> list = JSONArray.toCollection(JSONArray.fromObject(jsonStr), JsonBean.class);
      //DateUtil.getFormatDate(date,fmtstr)日期转字符串这里不再写代码了
for (JsonBean o : list) {
   System.out.println(DateUtil.getFormatDate(o.getBorn(), "yyyy-MM-dd"));
}

打印结果：
           1984-01-12
          1990-05-01
   2. JSON-》List、 Map
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String listStr = "["apple","orange"]";
Collection<String> strlist = JSONArray.toCollection(JSONArray.fromObject(listStr));
for (String str : strlist) {
    System.out.println(str);
}

String mapStr = "{"age":30,"name":"Michael","baby":["Lucy","Lily"]}";
Map<String, Object> map = (Map) JSONObject.toBean(JSONObject
                .fromObject(mapStr), Map.class);
for (Entry<String, Object> entry : map.entrySet()) {
    System.out.println(entry.getKey() + " " + entry.getValue());
}

打印结果：
            apple
           orange
           name Michael
           age 30
           baby [Lucy, Lily]