@Jsonproperty annotation

preface

@JsonProperty

When one Java Object conversion to Json After the string , Exceptions may occur if the actual name is not correct . For example, the coordinate name in the database is x_axis, And definition Java The target is xAxis, Then you need to use @JsonProperty annotation , And cooperate with ObjectMapper.writeValueAsString Method to deserialize an object into a string . The following example demo,

@JsonProperty(value = "", index = 1, access = JsonProperty.Access.xxx)

among value True name for member variable ,index For the sequence shown after serialization ,access Access control permissions for this object .

@Slf4j
public class JsonPropertyDemo {
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    @Builder
    @ToString
    private static class Coordinate {
        @JsonProperty(value = "x_axis", index = 1, access = JsonProperty.Access.WRITE_ONLY)
        private String xAxis;
        @JsonProperty(value = "y_axis", index = 2, access = JsonProperty.Access.READ_WRITE)
        private String yAxis;
        @JsonProperty(value = "z_axis", index = 3, access = JsonProperty.Access.READ_WRITE)
        private String zAxis;
    }

    public static void main(String[] args) {
        Coordinate coordinate = Coordinate.builder()
                .xAxis("113.58")
                .yAxis("37.86")
                .zAxis("40.05")
                .build();
        String jsonStr = JSON.toJSONString(coordinate);
        log.info("serializes the specified object into its equivalent Json representation :" + jsonStr);
        ObjectMapper mapper = new ObjectMapper();
        try {
            String str = mapper.writeValueAsString(coordinate);
            log.info("serialize any Java value as a String : " + str);
            Object bean = mapper.readerFor(Coordinate.class).readValue(str);
            log.info("read or update instances of specified type : " + bean);
        } catch (JsonProcessingException e) {
            log.error("error message : " + e);
        }
    }
}

Annotations are usually reflected to get mapped member variables and then enhanced ,@JsonProperty Serialize member variables into another name , And it is the actual name used in both serialization and deserialization .

@JsonAlias

com.fasterxml.jackson.annotation Medium @JsonProperty Can be used in serialization and deserialization , and @JsonAlias Only works in deserialization , Appoint Java More names that properties can accept . There are also links at the end of the article JsonAlias Instance source code , Here is a simple example ,

@Slf4j
public class JsonAliasDemo {
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    @Builder
    @ToString
    private static class Coordinate {
        @JsonAlias(value = "x_location")
        @JsonProperty(value = "x_axis")
        private String xAxis;
        @JsonProperty(value = "y_axis")
        @JsonAlias(value = "y_location")
        private String yAxis;
        @JsonProperty(value = "z_axis")
        @JsonAlias(value = "z_location")
        private String zAxis;
    }

    public static void main(String[] args) {
        String location = "{\"x_location\":\"113.58\",\"y_location\":\"37.86\",\"z_location\":\"40.05\"}";
        ObjectMapper mapper = new ObjectMapper();
        try {
            Object bean = mapper.readValue(location, Coordinate.class);
            log.info("read or update instances of specified type : " + bean);
        } catch (JsonProcessingException e) {
            log.error("error message : " + e);
        }
    }
}

@JsonAlias Alias in json character string , It can be recognized during deserialization , No deserialization failure , The results are as follows ,

 

Reference link ：

1、JSON On-line | JSON Parsing formatting —SO JSON Online tools

2、JsonProperty (Jackson JSON Processor)

3、Java class com.fasterxml.jackson.annotation.JsonProperty Instance source code - Programming dictionary

4、Java class com.fasterxml.jackson.annotation.JsonAlias Instance source code - Programming dictionary

5、Jackson data binding - You know