使用Jackson从String反序列化LocalDateTime

时间:2018-09-03 09:10:35

标签: java json jackson

我正在尝试将Jackson的String反序列化为LocalDateTime,但这是行不通的。

我有一个带有LocalDateTime字段的数据类:

@Data
public class Registration {
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd hh:mm:ss")
    private LocalDateTime timestamp;
}

我添加了特殊的Jackson数据类型模块:

compile("com.fasterxml.jackson.datatype:jackson-datatype-jsr310")

序列化可以很好地配合:

new ObjectMapper().registerModule(new JavaTimeModule()).writeValueAsString(registration);

结果字符串:

{"timestamp":"2018-09-03 10:09:35"}

但是反序列化不适用于:

new ObjectMapper().registerModule(new JavaTimeModule()).readValue(json.traverse(), Registration.class)

作为错误我得到:

Cannot deserialize value of type `java.time.LocalDateTime` from String "2018-09-03 10:09:35": 
    Failed to deserialize java.time.LocalDateTime: 
        (java.time.format.DateTimeParseException) Text '2018-09-03 10:09:35' could not be parsed: 
            Unable to obtain LocalDateTime from TemporalAccessor: 
                {MinuteOfHour=9, NanoOfSecond=0, SecondOfMinute=35, MicroOfSecond=0, MilliOfSecond=0, HourOfAmPm=10},
                ISO resolved to 2018-09-03 of type java.time.format.Parsed

我想念什么?我很困惑序列化有效,但是反序列化却无效。


MWE:(小型Gradle Java项目)

Main.java:

import java.io.IOException;
import java.time.LocalDateTime;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.core.TreeNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

public class Main {

    public static void main(String[] args) throws IOException {
        Registration registration = new Registration();
        registration.setTimestamp(LocalDateTime.now());

         ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule());

         String s = objectMapper.writeValueAsString(registration);
         TreeNode treeNode = objectMapper.readTree(s);

         //Fails here:
         Registration registration1 = objectMapper.readValue(treeNode.traverse(), Registration.class);

        System.out.println(registration1);
    }
}

class Registration {
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd hh:mm:ss")
    private LocalDateTime timestamp;

    public Registration() {
    }

    public LocalDateTime getTimestamp() {
        return this.timestamp;
    }

    public void setTimestamp(LocalDateTime localDateTime) {
        this.timestamp = localDateTime;
    }
}

build.gradle:

plugins {
    id 'java'
}

group 'dateMWE'
version '1.0-SNAPSHOT'

sourceCompatibility = 10

repositories {
    mavenCentral()
}

dependencies {
    compile("com.fasterxml.jackson.core:jackson-annotations:2.9.6")
    compile("com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.9.6")
}

2 个答案:

答案 0 :(得分:6)

问题与JSON反序列化无关,而与时间格式字符串有关:

pattern = "yyyy-MM-dd hh:mm:ss"

请注意,小时设置为hh:这是一个12小时格式程序,需要“ AM”或“ PM”值。

如果图案更改为

pattern = "yyyy-MM-dd HH:mm:ss"

问题应该解决。

答案 1 :(得分:1)

由于您正在使用new创建对象,因此Spring不会管理您的ObjectMapper。在配置文件中将ObjectMapper配置为Bean。您需要向DateTimeFormat注册LocalDateTimeDeserializer。然后在JavaTimeModule中设置反序列化器。

@Bean
 Public ObjectMapper objectMapper() {
   JavaTimeModule module = new JavaTimeModule();
   LocalDateTimeDeserializer localDateTimeDeserializer =  new 
   LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
   module.addDeserializer(LocalDateTime.class, localDateTimeDeserializer);
   ObjectMapper objectMapperObj = Jackson2ObjectMapperBuilder.json()
            .modules(module)
            .featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
            .build();
return objectMapperObj ;

在您的Spring配置中设置以上配置。