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JSON 即 JavaScript Object Natation，它是一種輕量級的數據交換格式，非常適合于服務器與 JavaScript 的交互。本文主要講解下java和JSON之間的轉換，特別是解決互相轉換遇到日期問題的情況。
一、需要相關的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
上面的包可以從下面的連接下載：
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());
打印結果：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());
打印結果：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());
打印結果：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"}
這時你會發現它把bean對象里的util.Date這個類型的所有屬性一一轉換出來。在實際運用過程中，大多數情況下我們希望能轉化為yyyy-MM-dd這種格式，下面就講一講如何實現：
首先要寫一個新的類JsonDateValueProcessor如下：
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/**
* JSON 日期格式處理（java轉化為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;
}
}
測試代碼：
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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());
打印結果：bean->json:{"age":1,"born":"2010-03-10","name":"NewBaby"}
這就能得到我們想要的結果了。
三、JSON-》java
1.如何把json的yyyy-MM-dd的轉換為Bean中的util.Date類型：
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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)日期轉字符串這里不再寫代碼了
for (JsonBean o : list) {
System.out.println(DateUtil.getFormatDate(o.getBorn(), "yyyy-MM-dd"));
}
打印結果：
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());
}
打印結果：
apple
orange
name Michael
age 30
baby [Lucy, Lily]