java与json互相转换(解决日期问题)

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    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和指定属性的过滤
    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
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
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
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"}
    4. bean->JSON 日期转换
   上面的例子中你会发现它把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:
/**
 * 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:
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。
4. java->JSON 过滤指定的属性
JsonBean bean = new JsonBean();
        bean.setName("NewBaby");
        bean.setAge(1);
        bean.setBorn(new Date());
        jo = JSONObject.fromObject(bean);

        JsonConfig jsonConfig = new JsonConfig();

        PropertyFilter filter = new PropertyFilter() {
            public boolean apply(Object source, String name, Object value) {
                if ("born".equals(name)) {
                    return true;
                }
                return false;
            }
        };
        jsonConfig.setJsonPropertyFilter(filter);

        njo = JSONObject.fromObject(bean, jsonConfig);
        System.out.println("bean->json [add property filter] :"
                + njo.toString());

打印结果:bean->json [add property filter] :{"age":1,"name":"NewBaby"}
从执行结果可以看出:born 这个属性已经成功过滤掉了。
三、JSON-》java
  1. 如何把json的yyyy-MM-dd的转换为Bean中的util.Date类型

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
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]

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