在Java中利用Jackson解析JSON数据

转化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;        /**       * 转化实体为json字符串       * @throws IOException       */      public static void writeEntity2Json() throws IOException{          System.out.println("使用JsonGenerator转化实体为json串-------------");          //writeObject可以转换java对象，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);      }      /**       * 转化Map为json字符串       * @throws JsonGenerationException       * @throws JsonMappingException       * @throws IOException       */      public static void writeMap2Json() throws JsonGenerationException, JsonMappingException, IOException{          System.out.println("转化Map为字符串--------");          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);      }      /**       * 转化List为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();            }      }  }

输出到浏览器端：

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());