我使用带有构建器模式的lombok构建了一个Java对象.但是,当我尝试使用Jackson反序列化Java对象时,我得到以下异常.对于具有@JsonProperty注释的字段会发生这种情况.

Exception in thread “main” com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field “user_name” (class User$UserBuilder), not marked as ignorable (2 known properties: “userName”, “userId”])
at [Source: (String)”{“userId”:1,”user_name”:”username”}”; line: 1, column: 26] (through reference chain: User$UserBuilder[“user_name”])

使用代码：

public class TestJson {
    public static void main(String args[]) throws Exception {
        ObjectMapper objectMapper = new ObjectMapper();

        User user = User.builder()
                .userName("username")
                .userId(1)
                .build();
        System.out.println(user);
        String string = objectMapper.writeValueAsString(user);
        System.out.println(string);
        user = objectMapper.readValue(string, User.class);
        System.out.println(user);
    }
}


@JsonDeserialize(builder = User.UserBuilder.class)
@Getter
@ToString
@Builder(toBuilder = true)
class User {
    @JsonProperty("user_name")
    @NonNull
    private String userName;

    @JsonProperty
    private int userId;

    @JsonPOJOBuilder(withPrefix = "")
    public static class UserBuilder {

    }
}

请帮我解决这个问题.

谢谢.

解决方法:

您收到此错误是因为Jackson不知道如何将user_name映射到任何UserBuilder字段.

你也需要在UserBuilder的userName字段上使用@JsonProperty(“user_name”),如下所示：

@JsonPOJOBuilder(withPrefix = "")
public static class UserBuilder {

    @JsonProperty("user_name")
    @NonNull
    private String userName;
}