jackson（三）序列化反序列化依赖于getter setter方法

拼搏现实的明天。 2023-02-08 12:50 3阅读 0赞

## 1.简介 ##

在默认情况下，ObjectMapper在序列化属性时会依赖getter方法。反序列化是会依赖setter方法。

## 2.测试默认情况 ##

/**
     * 测试用户
     * 将id 和 name属性的getter setter方法注释
     */
    @ToString
    @AllArgsConstructor
    @NoArgsConstructor
    @Accessors(chain = true)
    //@JsonInclude(value = JsonInclude.Include.NON_NULL)
    public class TestUser02 {
        
    //    @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 testUser022 = new TestUser02(1, "测试getter方法与序列化", 12, new Date());
            System.out.println("objectToJson >>>: " + JacksonUtil.object2Json(testUser022));
        }
    }
    
    // 测试结果 {"age":12,"createTime":1649213430746}
    // 发现字段`id` `name`,并没有被序列化 
    
    /**
     * 测试入口
     */
    public class TestJackson {
        
        public static void main(String[] args) {
        
            String json = "{\"id\": 1,\"name\":\"测试setter方法与反序列化\",\"age\":12,\"createTime\":1649214442782}";
            System.out.println("json2Object >>>: " + JacksonUtil.json2Object(json, TestUser02.class));
        }
    }
    
    // 测试结果 直接报异常 找不到属性“id”
    // com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "id" (class org.bj.core.jackson.TestUser02), not marked as ignorable (2 known properties: "createTime", "age"]) at [Source: (String)"{"id": 1,"name":"测试setter方法与序列化","age":12,"createTime":1649214442782}"; line: 1, column: 9]

由测试可知，在默认情况下，ObjectMapper在序列化属性时会依赖getter方法。反序列化是会依赖setter方法。

## 3.设置序列化反序列化不依赖getter setter ##

**方式一** ObjectMapper设置

ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.NONE)
    objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY)

**方式二** 使用注解@JsonAutoDetect

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
    public class TestUser02 {
        ...}

设置之后重新执行测试，会发现不管又没有getter setter方法都可以序列化 反序列化。

## 4.附录 jackson工具类 ##

/**
     * jackson 的工具类
     */
    public final class JacksonUtil {
        
        private static final ObjectMapper objectMapper;
    
        private JacksonUtil() {
        
        }
    
        static {
        
            objectMapper = new ObjectMapper()
                // 设置序列化反序列化采用直接处理字段的方式， 不依赖setter 和 getter
                // .setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.NONE)
                // .setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY)
            ;
        }
    
        /**
         * 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;
        }
    }