Java：jackson处理LocalDateTime序列化的时候报错InvalidDefinitionException

(目录)

问题描述

jackson处理LocalDateTime序列化的时候报错

ObjectMapper mapper = new ObjectMapper();

mapper.writeValueAsString(LocalDateTime.now());

报错信息

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: 
Java 8 date/time type `java.time.OffsetDateTime` not supported by default: 
add Module "com.fasterxml.jackson.datatype:jackson-datatype-jsr310" to enable handling

如果处理Date对象是不会报错的

ObjectMapper mapper = new ObjectMapper();

mapper.writeValueAsString(new Date());
// 1684480558531

解决方法

按照异常信息提示，引入模块com.fasterxml.jackson.datatype:jackson-datatype-jsr310

引入依赖

<!-- json -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.4</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
    <version>2.13.4</version>
</dependency>

注册JavaTimeModule

ObjectMapper mapper = new ObjectMapper();

// 已过时
// mapper.registerModule(new JSR310Module());
// Jackson 2.7 之后使用JavaTimeModule
mapper.registerModule(new JavaTimeModule());

// 默认输出
mapper.writeValueAsString(LocalDateTime.now())
[2023,5,19,15,21,57,337000000]

发现输出的格式不太对，进一步优化

ObjectMapper mapper = new ObjectMapper();

JavaTimeModule javaTimeModule = new JavaTimeModule();
// 设置序列化格式
javaTimeModule.addSerializer(LocalDateTime.class,
        new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
mapper.registerModule(javaTimeModule);

try {
    System.out.println(mapper.writeValueAsString(LocalDateTime.now()));
    // "2023-05-19 15:29:01"
} catch (JsonProcessingException e) {
    e.printStackTrace();
}

完整测试代码

package com.example.demo;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
import org.junit.jupiter.api.Test;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class JsonTest {
    @Test
    public void testJavaTimeModule() {
        ObjectMapper mapper = new ObjectMapper();

        JavaTimeModule javaTimeModule = new JavaTimeModule();
        // 设置序列化格式
        javaTimeModule.addSerializer(LocalDateTime.class,
                new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
        mapper.registerModule(javaTimeModule);

        try {
            System.out.println(mapper.writeValueAsString(LocalDateTime.now()));
            // "2023-05-19 15:29:01"
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
    }
}

参考 使用Jackson JSR310模块反序列化LocalDateTime