序列化注解

@JsonAnyGetter

用于指定一个方法，将对象中的所有属性序列化为一个 Map 对象。

@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;
    private Map<String, String> properties = new HashMap<>();

    @JsonAnyGetter
    public Map<String, String> getProperties() {
        return properties;
    }

    public void add(String key, String value) {
        properties.put(key, value);
    }
}

User user = User.builder().username("job").age(18).properties(new HashMap<>()).build();
user.add("city", "beijing");
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：{"username":"job","age":18,"city":"beijing"}

@JsonGetter

用于指定一个方法，将对象中的属性序列化为指定的属性名。

@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;

    @JsonGetter("name")
    public String getUsername() {
        return username;
    }
}

{"age":18,"name":"job"}

User user = User.builder().username("job").age(18).build();
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：{"age":18,"name":"job"}

@JsonPropertyOrder

用于指定序列化时属性的顺序。

@JsonPropertyOrder({"age", "username"})
@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;
}

User user = User.builder().username("job").age(18).build();
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：{"age":18,"username":"job"}

@JsonRawValue

用于指定一个属性，将属性值按照原始的 JSON 字符串序列化。

@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;
    @JsonRawValue
    private String properties;
}

User user = User.builder().username("job").age(18).properties("{\"city\":\"beijing\"}").build();
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：{"username":"job","age":18,"properties":{"city":"beijing"}}
// 如果不使用 @JsonRawValue 注解，打印结果：{"username":"job","age":18,"properties":"{\"city\":\"beijing\"}"}

@JsonValue

用于属性或方法，指定序列化时的值，此时，只会序列化该值。一个类中只能有一个方法使用 @JsonValue 注解。

@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;

    @JsonValue
    public String getUsername() {
        return username;
    }
}

User user = User.builder().username("job").age(18).build();
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：job

@JsonRootName

用于指定序列化时的根节点名称。

@JsonRootName("user")
@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;
}

User user = User.builder().username("job").age(18).build();
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：{"user":{"username":"job","age":18}}

@JsonSerialize

用于指定自定义的序列化器。

@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String username;
    private Integer age;

    @JsonSerialize(using = CustomSerializer.class)
    private String properties;
}

public class CustomSerializer extends JsonSerializer<String> {
    @Override
    public void serialize(String value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        gen.writeString("custom-" + value);
    }
}

User user = User.builder().username("job").age(18).properties("beijing").build();
String userStr = objectMapper.writeValueAsString(user);
// 打印结果：{"username":"job","age":18,"properties":"custom-beijing"}