当我将实体转换为JSON时，为什么localdate格式改变了

Question

我的目标是将日期存储到数据库中。要执行此应用，我使用Springboot，JPA，H2，...

我使用 LocalDate，而格式为 yyyy-MM-dd。

实体

@Entity
public class MyObject {
    @Id
    private String id;
    private LocalDate startdate;
    private LocalDate enddate;
    public MyObject() {}
    public MyObject(LocalDate enddate) {
        this.startdate = LocalDate.now();
        this.enddate = enddate;
    }
    ...
}

MAIN

private DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
MyObject myObject = new MyObject(LocalDate.parse("2019-03-01", formatter));
myObject.setId(UUID.randomUUID().toString());
myObjectResource.save(myObject);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
System.out.println(myObject.getStartdate()); // 2019-02-23
System.out.println(myObject.getEnddate()); // 2019-03-01
HttpEntity<String> entity = new HttpEntity<>(this.toJsonString(myObject), headers);
System.out.println(entity.toString()); // <{"id":"ba6649e4-6e65-4f54-8f1a-f8fc7143b05a","startdate":{"year":2019,"month":"FEBRUARY","dayOfMonth":23,"dayOfWeek":"SATURDAY","era":"CE","dayOfYear":54,"leapYear":false,"monthValue":2,"chronology":{"id":"ISO","calendarType":"iso8601"}},"enddate":{"year":2019,"month":"MARCH","dayOfMonth":1,"dayOfWeek":"FRIDAY","era":"CE","dayOfYear":60,"leapYear":false,"monthValue":3,"chronology":{"id":"ISO","calendarType":"iso8601"}}},[Content-Type:"application/json"]>
private String toJsonString(Object o) throws Exception {
    ObjectMapper om = new ObjectMapper();
    return om.writeValueAsString(o);
}

您能帮我了解为什么entity.toString()中的日期与getMethods()不一样？

感谢您的帮助！

Answer 1

LocalDate.parse返回一个新的 LocalDate对象。DateTimeFormatter中指定的格式选项丢失了。

Jackson（您使用的JSON库）不知道您以前是如何"格式化" LocalDate的，因此它使用自己的格式。

您可以注册JavaTimeModule

final ObjectMapper om = new ObjectMapper();
om.registerModule(new JavaTimeModule());

或您可以提供自定义JsonSerializer<T>。