ObjectMapper将josn字符串转化为List

一.利用ObjectMapper将json字符串转为List

Student.java

package objectmapper;

import java.io.Serializable;

public class Student{
    private Integer id;
    private String sName;
    private String sAddress;
    private Double sal;
    
    public Student() {
    }
    public Student(Integer id, String sName, String sAddress, Double sal) {
        super();
        this.id = id;
        this.sName = sName;
        this.sAddress = sAddress;
        this.sal = sal;
    }
    //get/set
    
}

ZcjUser.java

package objectmapper;public class ZcjUser implements Serializable {

    private static final long serialVersionUID = 1L;
    private int id;
    private String message;
    private Date sendTime;

    // 这里手写字母大写，只是为了测试使用，是不符合java规范的
    private String NodeName;
    private List<Integer> intList;
    private List<Student> studentList;
public ZcjUser(int id, String message, Date sendTime) {
        super();
        this.id = id;
        this.message = message;
        this.sendTime = sendTime;
　　}
   //get/set
}

Test.java

package objectmapper;public class Test {
    public static ObjectMapper mapper = new ObjectMapper();

    static {
        // 转换为格式化的json
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        // 如果json中有新增的字段并且是实体类类中不存在的，不报错
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    }
    
    public static void main(String[] args) throws Exception {
        testObj();
    }
    public static void testObj() throws JsonGenerationException, JsonMappingException, IOException {
        ZcjUser user = new ZcjUser(1, "Hello World", new Date());
       
        List<Integer> intList = new ArrayList<>();
        intList.add(11);
        intList.add(22);
        intList.add(33);
        user.setIntList(intList);
        
        List<Student> sList = new ArrayList<>();
        Student s1 = new Student(1, "zs", "四川", 111.1);
        Student s2 = new Student(2, "ls", "成都", 222.2);
        Student s3 = new Student(3, "ww", "兴隆湖", 333.3);
        sList.add(s1);
        sList.add(s2);
        sList.add(s3);
        user.setStudentList(sList);
        
        
        List<ZcjUser> userList = new ArrayList<>();
        userList.add(user);

        mapper.writeValue(new File("D:/test3.txt"), userList); // 写到文件中

        List<ZcjUser> lendReco = mapper.readValue(new File("D:/test3.txt"),new TypeReference<List<ZcjUser>>() { });
        System.out.println(lendReco.get(0).getStudentList().get(0).getsName());

    }

}

test3.txt

[ {
  "id" : 1,
  "message" : "Hello World",
  "sendTime" : 1557823326329,
  "intList" : [ 11, 22, 33 ],
  "studentList" : [ {
    "id" : 1,
    "sName" : "zs",
    "sAddress" : "四川",
    "sal" : 111.1
  }, {
    "id" : 2,
    "sName" : "ls",
    "sAddress" : "成都",
    "sal" : 222.2
  }, {
    "id" : 3,
    "sName" : "ww",
    "sAddress" : "兴隆湖",
    "sal" : 333.3
  } ],
  "nodeName" : null
} ]

二。利用JSONArray将json字符串转List

Test.java

public class Test {
    
    public static void main(String[] args) throws Exception {
        testObj();
    }
    public static void testObj() throws JsonGenerationException, JsonMappingException, IOException {
        String jsonStr = FileUtils.readFileToString(new File("D:/test3.txt"), "utf-8");
        
        Map<String,Class<Student>> map = new HashMap<String,Class<Student>>();
        // studentList 为ZcjUser的属性
        map.put("studentList", Student.class);
        JSONArray array = JSONArray.fromObject(jsonStr);
        List<ZcjUser> list2 = (List<ZcjUser>) JSONArray.toList(array, ZcjUser.class,map);
        
        System.out.println(list2.get(0).getStudentList().get(0).getsName());
    }

}