jackson（二）序列化空值null字段

太过爱你忘了你带给我的痛 2023-02-08 12:50 21阅读 0赞

## 1.简介 ##

在默认情况下，ObjectMapper在序列化时，会将所有的字段序列化，无论这些字段是否有值

## 2.测试默认情况 ##

/**
     * 测试用户
     */
    @ToString
    @Accessors(chain = true)
    public class TestUser {
        
        @Setter
        @Getter
        private Integer id;
        @Setter
        @Getter
        private String name;
        @Setter
        @Getter
        private Integer age;
        @Setter
        @Getter
        private Date createTime;
    }
    
    /**
     * 测试入口
     */
    public class TestJackson {
        
        public static void main(String[] args) {
        
            TestUser02 testUser021 = new TestUser02().setName("XXXX");
            System.out.println("objectToJson >>>: " + JacksonUtil.object2Json(testUser021));
        }
    }
    
    // 输出结果
    // objectToJson >>>: {"id":null,"name":"XXXX","age":null,"createTime":null}

## 4.设置空值不序列化 ##

**方式一** ObjectMapper设置setSerializationInclusion(JsonInclude.Include.NON\_NULL)

ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

**方式二** 类设置注解@JsonInclude(value= JsonInclude.Include.NON\_NULL)

@JsonInclude(value= JsonInclude.Include.NON_NULL)
    public class TestUser {
        ...}

**方式三** 字段设置注解@JsonInclude(value= JsonInclude.Include.NON\_NULL)

public class TestUser {
        
        @JsonInclude(value= JsonInclude.Include.NON_NULL)
        private Integer id;
    }

## 3.测试空值不序列化 ##

/**
     * 测试用户
     */
    @ToString
    @Accessors(chain = true)
    @JsonInclude(value= JsonInclude.Include.NON_NULL)
    public class TestUser {
        
        @Setter
        @Getter
        private Integer id;
        @Setter
        @Getter
        private String name;
        @Setter
        @Getter
        private Integer age;
        @Setter
        @Getter
        private Date createTime;
    }
    
    /**
     * 测试入口
     */
    public class TestJackson {
        
        public static void main(String[] args) {
        
            TestUser02 testUser021 = new TestUser02().setName("XXXX");
            System.out.println("objectToJson >>>: " + JacksonUtil.object2Json(testUser021));
        }
    }
    
    // 输出结果
    // objectToJson >>>: {"name":"XXXX"}

## 5.附录 jackson工具类 ##

/**
     * jackson的工具类
     */
    public class JacksonUtil {
        
        private static final ObjectMapper objectMapper;
    
        static {
        
            objectMapper = new ObjectMapper()
                // .setSerializationInclusion(JsonInclude.Include.NON_NULL)
                ;
        }
    
        /**
         * json字符串 转成 java对象
         *
         * @param json json字符串
         * @param cls  java类型
         * @return {@link T}
         */
        public static <T> T json2Object(String json, Class<T> cls) {
        
            T t = null;
            try {
        
                t = objectMapper.readValue(json, cls);
            } catch (JsonProcessingException e) {
        
                e.printStackTrace();
            }
            return t;
        }
    
        /**
         * java对象 转成 json字符串
         *
         * @param obj java对象
         * @return {@link String}
         */
        public static String object2Json(Object obj) {
        
            String json = null;
            try {
        
                json = objectMapper.writeValueAsString(obj);
            } catch (JsonProcessingException e) {
        
                e.printStackTrace();
            }
            return json;
        }
    }