在Java中利用Jackson解析JSON數據

轉化json字符串：

/**


使用Jackson生成json格式字符串

@author archie2010 since 2011-4-26下午05:59:46
*/
public class JacksonTest {
private static JsonGenerator jsonGenerator = null;
 private static ObjectMapper objectMapper = null;
 private static User user = null;
/**

轉化實體為json字符串
@throws IOException
*/
public static void writeEntity2Json() throws IOException{
 System.out.println("使用JsonGenerator轉化實體為json串-------------");
 //writeObject可以轉換java對象，eg:JavaBean/Map/List/Array等
 jsonGenerator.writeObject(user);
 System.out.println();
 System.out.println("使用ObjectMapper-----------");
 //writeValue具有和writeObject相同的功能
 objectMapper.writeValue(System.out, user);
}
/**
轉化Map為json字符串
@throws JsonGenerationException
@throws JsonMappingException
@throws IOException
*/
public static void writeMap2Json() throws JsonGenerationException, JsonMappingException, IOException{
 System.out.println("轉化Map為字符串--------");
 Map<String, Object> map=new HashMap<String, Object>();
 map.put("uname", user.getUname());
 map.put("upwd", user.getUpwd());
 map.put("USER", user);
 objectMapper.writeValue(System.out, map);
}
/**
轉化List為json字符串
@throws IOException 
@throws JsonMappingException 
@throws JsonGenerationException 
*/
public static void writeList2Json() throws IOException{
 List<User> userList=new ArrayList<User>();
 userList.add(user);
User u=new User();
 u.setUid(10);
 u.setUname("archie");
 u.setUpwd("123");
 userList.add(u);
 objectMapper.writeValue(System.out, userList);





    objectMapper.writeValue(System.out, userList);
}
public static void main(String[] args) {
    user = new User();
    user.setUid(5);
    user.setUname("tom");
    user.setUpwd("123");
    user.setNumber(3.44);
    objectMapper = new ObjectMapper();
    try {
        jsonGenerator = objectMapper.getJsonFactory().createJsonGenerator(System.out, JsonEncoding.UTF8);
        //writeEntity2Json();
        //writeMap2Json();
        writeList2Json();
    } catch (IOException e) {

        e.printStackTrace();

    }
}

}</pre>[{"number":3.44,"uname":"tom","upwd":"123","uid":5},{"number":0.0,"uname":"archie","upwd":"123","uid":10}] 
輸出到瀏覽器端： 

StringWriter writer = new StringWriter();
ObjectMapper mapper = new ObjectMapper();
  try {
   mapper.writeValue(writer, hMap);
  } catch (JsonGenerationException e) {
   e.printStackTrace();
  } catch (JsonMappingException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }

response.setContentType("text/html;charset=UTF-8");
PrintWriter out= response.getWriter();
out.print(writer.toString());</pre> 
 
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