bean转json时null字段不转换的方法

原文地址：https://blog.csdn.net/lom9357bye/article/details/61926037

1.使用GSON时，默认不对null字段进行转换，而ObjectMapper和JSONObject默认对null字段进行转换

（1）使用GSON时，对null字段进行转换的设置

 Gson gsonSerializeNull = new GsonBuilder().serializeNulls().create();

（2）使用ObjectMapper对null字段不进行转换的设置

ObjectMapper objectMapper= new ObjectMapper();

objectMapper.setSerializationInclusion(Include.NON_NULL);

（3）使用json-lib的JSONObject在bean转json时对null字段不转换的设置

 PropertyFilter filter = new PropertyFilter() {

            public boolean apply(Object object, String fieldName,

                    Object fieldValue) {

                return null == fieldValue;

            }

        };

        jsonConfig.setJsonPropertyFilter(filter);

        System.out.println(JSONObject.fromObject(s, jsonConfig).toString());

2.测试

Student类

package com.beanjson.test;


public class Student {

    private String name;
 
    private int id;
 
    private Integer age = null;

    public Student() {

    }

    public String getName() {
        return name;
    }

 
    public void setName(String name) {
        this.name = name;
    }

 
    public int getId() {
        return id;
    }

 
    public void setId(int id) {
        this.id = id;
    }


    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

}

main函数

package com.beanjson.test;

 

import net.sf.json.JSONObject;

import net.sf.json.JsonConfig;

import net.sf.json.util.PropertyFilter;

 

import com.fasterxml.jackson.annotation.JsonInclude.Include;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.ObjectMapper;

import com.google.gson.Gson;

import com.google.gson.GsonBuilder;

 

public class Test {

 

    private static ObjectMapper objectMapper;

 

    public static void main(String[] args) throws JsonProcessingException {

        Student s = new Student();

        s.setName("abc");

        s.setId(1);

        s.setAge(null);

 

        System.out.println("----------gson(默认对null不转换)---------");

        Gson gson = new Gson();

        System.out.println(gson.toJson(s));

        System.out.println("----------gson(对null字段转换)---------");

        Gson gsonSerializeNull = new GsonBuilder().serializeNulls().create();

        System.out.println(gsonSerializeNull.toJson(s));

 

        System.out.println("----------objectMapper对null字段不转换的设置---------");

        objectMapper = new ObjectMapper();

        objectMapper.setSerializationInclusion(Include.NON_NULL);

        System.out.println(objectMapper.writeValueAsString(s));

 

        System.out.println("----------json-lib对null字段不转换的设置---------");

        JsonConfig jsonConfig = new JsonConfig();

        PropertyFilter filter = new PropertyFilter() {

            public boolean apply(Object object, String fieldName,

                    Object fieldValue) {

                return null == fieldValue;

            }

        };

        jsonConfig.setJsonPropertyFilter(filter);

        System.out.println(JSONObject.fromObject(s, jsonConfig).toString());

    }

 

}