使用Jackson定制化某字段的序列化/反序列化（Jackson – Decide What Fields Get Serialized/Deserialized）

痛定思痛。 2024-03-23 18:06 61阅读 0赞

#### 目录 ####

*  A Public Field
 *   *  有get，set方法时，则序列化/反序列化都支持
     *  无get，set方法时，则序列化/反序列化仅支持public
     *   *  反序列化Non-Public Field报错
 *  A Getter Makes a Non-Public Field Serializable and Deserializable
 *   *  有get方法的Non-Public Field支持序列化和反序列化
     *  Json串反序列化时，包含无get方法的Non-Public Field报错
 *  A Setter Makes a Non-Public Field Deserializable Only
 *   *  the setter should only make the field deserializable, but not serializable:
     *  只能解析有set方法属性，否则报错
 *  Make All Fields Globally Serializable
 *  Change the Name of a Property on Serialization/Deserialization
 *  Ignore a Field on Serialization or Deserialization

--------------------

## A Public Field ##

### 有get，set方法时，则序列化/反序列化都支持 ###

@Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class MyDtoAccessLevel {
        
        private String stringValue;
        int intValue;
        protected float floatValue;
        public boolean booleanValue;
    }

MyDtoAccessLevel dtoObject = new MyDtoAccessLevel();
    
    ObjectMapper mapper = new ObjectMapper();
    String dtoAsString = mapper.writeValueAsString(dtoObject);
    System.out.println(dtoAsString);
    
    String jsonAsString = "{\"stringValue\":\"dtoString\"}";
    MyDtoAccessLevel dtoObject1 = mapper.readValue(jsonAsString, MyDtoAccessLevel.class);
    System.out.println(dtoObject1);
    
    执行结果
    {
        "stringValue":null,"intValue":0,"floatValue":0.0,"booleanValue":false}
    MyDtoAccessLevel(stringValue=dtoString, intValue=0, floatValue=0.0, booleanValue=false)

--------------------

### 无get，set方法时，则序列化/反序列化仅支持public ###

public class MyDtoAccessLevel {
        
        private String stringValue;
        int intValue;
        protected float floatValue;
        public boolean booleanValue;
    
        @Override
        public String toString() {
        
            return "MyDtoAccessLevel{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + ", floatValue=" + floatValue + ", booleanValue=" + booleanValue + '}';
        }
    }

MyDtoAccessLevel dtoObject = new MyDtoAccessLevel();
    
    ObjectMapper mapper = new ObjectMapper();
    String dtoAsString = mapper.writeValueAsString(dtoObject);
    System.out.println(dtoAsString);
    
    String jsonAsString = "{\"booleanValue\":false}";
    MyDtoAccessLevel dtoObject1 = mapper.readValue(jsonAsString, MyDtoAccessLevel.class);
    System.out.println(dtoObject1);
    
    结果
    {
        "booleanValue":false}
    MyDtoAccessLevel{
        stringValue='null', intValue=0, floatValue=0.0, booleanValue=false}

#### 反序列化Non-Public Field报错 ####

String jsonAsString = "{\"booleanValue\":false,\"stringValue\":\"dtoString\"}";
    MyDtoAccessLevel dtoObject1 = mapper.readValue(jsonAsString, MyDtoAccessLevel.class);
    System.out.println(dtoObject1);
    
    Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "stringValue" (class javabasic.enumprac.MyDtoAccessLevel), not marked as ignorable (one known property: "booleanValue"])
     at [Source: (String)"{"booleanValue":false,"stringValue":"dtoString"}"; line: 1, column: 38] (through reference chain: javabasic.enumprac.MyDtoAccessLevel["stringValue"])

--------------------

## A Getter Makes a Non-Public Field Serializable and Deserializable ##

public class MyDtoWithGetter {
        
        private String stringValue;
        private int intValue;
    
        public String getStringValue() {
        
            return stringValue;
        }
    
        @Override
        public String toString() {
        
            return "MyDtoWithGetter{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + '}';
        }
    }

### 有get方法的Non-Public Field支持序列化和反序列化 ###

ObjectMapper mapper = new ObjectMapper();
    MyDtoWithGetter dtoObject = new MyDtoWithGetter();
    String dtoAsString = mapper.writeValueAsString(dtoObject);
    System.out.println(dtoAsString);
    
    String jsonAsString = "{\"stringValue\":\"dtoString\"}";
    MyDtoWithGetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithGetter.class);
    System.out.println(dtoObject1);
    
    结果
    {
        "stringValue":null}
    MyDtoWithGetter{
        stringValue='dtoString', intValue=0}

### Json串反序列化时，包含无get方法的Non-Public Field报错 ###

String jsonAsString = "{\"intValue\":11,\"stringValue\":\"dtoString\"}";
    MyDtoWithGetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithGetter.class);
    
    Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "intValue" (class javabasic.enumprac.MyDtoWithGetter), not marked as ignorable (one known property: "stringValue"])
     at [Source: (String)"{"intValue":11,"stringValue":"dtoString"}"; line: 1, column: 15] (through reference chain: javabasic.enumprac.MyDtoWithGetter["intValue"])

--------------------

## A Setter Makes a Non-Public Field Deserializable Only ##

public class MyDtoWithSetter {
        
        private String stringValue;
        private int intValue;
    
        public void setIntValue(int intValue) {
        
            this.intValue = intValue;
        }
    
        @Override
        public String toString() {
        
            return "MyDtoWithSetter{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + '}';
        }
    }

### the setter should only make the field deserializable, but not serializable: ###

ObjectMapper mapper = new ObjectMapper();
    MyDtoWithSetter  dtoObject = new MyDtoWithSetter ();
    String dtoAsString = mapper.writeValueAsString(dtoObject);
    System.out.println(dtoAsString);
    
    Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class javabasic.enumprac.MyDtoWithSetter and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)

### 只能解析有set方法属性，否则报错 ###

ObjectMapper mapper = new ObjectMapper();
    String jsonAsString = "{\"intValue\":1}";
    MyDtoWithSetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithSetter.class);
    System.out.println(dtoObject1);
    
    MyDtoWithSetter{
        stringValue='null', intValue=1}

ObjectMapper mapper = new ObjectMapper();
    String jsonAsString = "{\"stringValue\":\"dtoString\",\"intValue\":\"22\"}";
    MyDtoWithSetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithSetter.class);
    System.out.println(dtoObject1);
    
    Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "stringValue" (class javabasic.enumprac.MyDtoWithSetter), not marked as ignorable (one known property: "intValue"])
     at [Source: (String)"{"stringValue":"dtoString","intValue":"22"}"; line: 1, column: 17] (through reference chain: javabasic.enumprac.MyDtoWithSetter["stringValue"])

## Make All Fields Globally Serializable ##

MyDtoAccessLevel dtoObject = new MyDtoAccessLevel();
    
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
    
    String dtoAsString = mapper.writeValueAsString(dtoObject);
    
    System.out.println(dtoAsString);
    
    {
        "stringValue":null,"intValue":0,"floatValue":0.0,"booleanValue":false}

--------------------

## Change the Name of a Property on Serialization/Deserialization ##

MyDto dtoObject = new MyDto();
      dtoObject.setStringValue("a");
      
     ObjectMapper mapper = new ObjectMapper();
     String dtoAsString = mapper.writeValueAsString(dtoObject);
     
     System.out.println(dtoAsString);

public class MyDto {
        
        private String stringValue;
    
        public MyDto() {
        
            super();
        }
    
        public String getStringValue() {
        
            return stringValue;
        }
    
        public void setStringValue(String stringValue) {
        
            this.stringValue = stringValue;
        }
    }
    
    结果
    {
        "stringValue":"a"}

public class MyDto {
        
        private String stringValue;
    
        public MyDto() {
        
            super();
        }
    
        @JsonProperty("strVal")
        public String getStringValue() {
        
            return stringValue;
        }
    
        public void setStringValue(String stringValue) {
        
            this.stringValue = stringValue;
        }
    }
    
    结果
    {
        "strVal":"a"}

--------------------

## Ignore a Field on Serialization or Deserialization ##

**Further reading: [Jackson Ignore Properties on Marshalling][]**

通过在getter上添加`@JsonIgnore`注释`禁止`该字段的序列化，  
通过在setter上应用`@JsonProperty`注释来`启用`该字段的反序列化

public class User {
        
        public String name;
        private String password;
    
        @JsonIgnore
        public String getPassword() {
        
            return password;
        }
    
        @JsonProperty
        public void setPassword(String password) {
        
            this.password = password;
        }
    
        @Override
        public String toString() {
        
            return "User{" + "name='" + name + '\'' + ", password='" + password + '\'' + '}';
        }
    }

User userObject = new User();
    userObject.setPassword("thePassword");
    userObject.setPassword("mingming");
    
    ObjectMapper mapper = new ObjectMapper();
    String userAsString = mapper.writeValueAsString(userObject);
    System.out.println(userAsString);
    
    String jsonAsString = "{\"name\":\"mingming\",\"password\":\"thePassword\"}";
    User userObject1 = mapper.readValue(jsonAsString, User.class);
    System.out.println(userObject1);
    
    结果：
    {
        "name":null}
    User{
        name='mingming', password='thePassword'}

\-----------------------------------------------------------------------------读书笔记摘自 文章：**[Jackson – Decide What Fields Get Serialized/Deserialized][Jackson _ Decide What Fields Get Serialized_Deserialized]**

[Jackson Ignore Properties on Marshalling]: https://www.baeldung.com/jackson-ignore-properties-on-serialization
[Jackson _ Decide What Fields Get Serialized_Deserialized]: https://www.baeldung.com/jackson-field-serializable-deserializable-or-not