1. Jackson

坐标

  1.     <dependency>
  2.       <groupId>com.fasterxml.jackson.core</groupId>
  3.       <artifactId>jackson-databind</artifactId>
  4.       <version>2.9.0</version>
  5.     </dependency>
  6.     <dependency>
  7.       <groupId>com.fasterxml.jackson.core</groupId>
  8.       <artifactId>jackson-core</artifactId>
  9.       <version>2.9.0</version>
  10.     </dependency>
  11.     <dependency>
  12.       <groupId>com.fasterxml.jackson.core</groupId>
  13.       <artifactId>jackson-annotations</artifactId>
  14.       <version>2.9.0</version>
  15.     </dependency>

Jackson是把JSON 转为java对象或者集合的一个工具类

SpringMVC 转换默认使用 Jackson

  • ObjectMapper 实现JSON字符串和对象之间的转换

    • writeValueAsString(object obj) 将java对象转为json字符串
    • <T> T readValue(String json,class<T> valueTType) 将json字符串转为java对象
    • <T> T readValue(String json,TypeReferncevalueTType) 将json字符串转为java对象
  • TypeReference 对集合泛型的反序列化
  1. private ObjectMapper mapper =new ObjectMapper();
  2. user user = new user("张三",23);
  3. //对象转json
  4. String json = mapper.writeValueAsString(user);
  5. System.out.println(json);
  7. //json转对象
  8. user user1 = mapper.readValue(json, user.class);
  9. System.out.println(user1);
  11. //map转json
  12. HashMap<String,String> map =new HashMap<>();
  13. map.put("姓名","张三");
  14. map.put("性别","男");
  15. String s = mapper.writeValueAsString(map);
  16. System.out.println(s);
  18. //json转map
  19. HashMap<String,String> hashMap = mapper.readValue(s, HashMap.class);
  20. System.out.println(hashMap);
  22. //map<String,user> 转json
  23. HashMap<String,user> map2 =new HashMap<>();
  24. map2.put("一班",new user("张三",23));
  25. map2.put("二班",new user("李四",23));
  26. String s1 = mapper.writeValueAsString(map2);
  27. System.out.println(s1);
  30. //json转 map<String,user>
  31. HashMap<String,user> map3=mapper.readValue(s1,new TypeReference<HashMap<String,user>>(){});
  32. System.out.println(map3);
  34. //List<String> 换json
  35. ArrayList<String> list=new ArrayList<>();
  36. list.add("张三");
  37. list.add("李四");
  38. String s2 = mapper.writeValueAsString(list);
  39. System.out.println(s2);
  41. //List<String> 转json
  42. ArrayList arrayList = mapper.readValue(s2, ArrayList.class);
  43. System.out.println(arrayList);
  45. //List<user> 换json
  46. ArrayList<user> list2=new ArrayList<>();
  47. list2.add(new user("张三",23));
  48. list2.add(new user("王五",22));
  49. String s3 = mapper.writeValueAsString(list2);
  50. System.out.println(s3);
  52. //List<user> 转json
  53. ArrayList<user> arrayList2 = mapper.readValue(s3, new TypeReference<ArrayList<user>>(){});
  54. System.out.println(arrayList2);