java - LocalDate 序列化 csv 时出现 jackson-dataformat-csv 错误

Question

我尝试以两种方式序列化包含 java.time.LocalDate 的对象，但都失败了。

1. 使用 @JsonUnwrapped 和 @JsonFormat(shape=JsonFormat.Shape.STRING) 进行注释会出现错误:

   Exception in thread "main" com.fasterxml.jackson.dataformat.csv.CsvMappingException: CSV generator does not support Object values for properties (nested Objects) (through reference chain: java.util.ArrayList[0]->models.DateRange["finish"]->java.time.LocalDate["chronology"])

@Data
@AllArgsConstructor
@NoArgsConstructor
//@JsonFormat(shape=JsonFormat.Shape.STRING)
public class DateRange {
  @JsonUnwrapped
  @JsonFormat(shape=JsonFormat.Shape.STRING)
  private LocalDate start;
  @JsonUnwrapped
  @JsonFormat(shape=JsonFormat.Shape.STRING)
  private LocalDate finish;
}

--------
public class CsvPractice {
  public static void main(String[] args) throws JsonProcessingException {
    ArrayList<DateRange> csv = Lists.newArrayList();
    for (int i = 1; i < 6; i++) {
      csv.add(new DateRange(LocalDate.now().plusDays(i), LocalDate.now().plusDays(i + 1)));
    }
    CsvMapper mapper = new CsvMapper();
//    mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
    CsvSchema schema = mapper.schemaFor(DateRange.class).withHeader();
    System.out.println(mapper.writer(schema).writeValueAsString(csv));
  }
}

配置映射器 mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS); 没有对象上的注释，但得到:

Exception in thread "main" com.fasterxml.jackson.dataformat.csv.CsvMappingException: CSV generator does not support Object values for properties (nested Objects) (through reference chain: java.util.ArrayList[0]->models.DateRange["finish"])

@Data
@AllArgsConstructor
@NoArgsConstructor
//@JsonFormat(shape=JsonFormat.Shape.STRING)
public class DateRange {
//  @JsonUnwrapped
//  @JsonFormat(shape=JsonFormat.Shape.STRING)
  private LocalDate start;
//  @JsonUnwrapped
//  @JsonFormat(shape=JsonFormat.Shape.STRING)
  private LocalDate finish;
}
---------
public class CsvPractice {
  public static void main(String[] args) throws JsonProcessingException {
    ArrayList<DateRange> csv = Lists.newArrayList();
    for (int i = 1; i < 6; i++) {
      csv.add(new DateRange(LocalDate.now().plusDays(i), LocalDate.now().plusDays(i + 1)));
    }
    CsvMapper mapper = new CsvMapper();
    mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
    CsvSchema schema = mapper.schemaFor(DateRange.class).withHeader();
    System.out.println(mapper.writer(schema).writeValueAsString(csv));
  }
}

我的 jackson 版本是:

    <dependency>
      <groupId>com.fasterxml.jackson.dataformat</groupId>
      <artifactId>jackson-dataformat-csv</artifactId>
      <version>2.9.8</version>
    </dependency>

我错过了什么吗？

引用

• jackson-dataformat-csv: cannot serialize LocalDate
• https://github.com/FasterXML/jackson-dataformat-csv/issues/135

Answer 1

您的代码即将完成。您的问题是您的映射器未正确序列化 LocalDate 。

要启用 Jackson 对 Java 8 日期和时间类型的序列化，您需要包含以下模块:

https://mvnrepository.com/artifact/com.fasterxml.jackson.datatype/jackson-datatype-jsr310/2.10.1

完成此操作后，您需要修改代码以注册 Jackson 的 JSR-310 模块，然后指示它禁用 SerializationFeature.WRITE_DATES_AS_TIMESTAMPS。

因此，基于上述内容，包含该模块，然后只需进行以下代码更改:

CsvMapper mapper = new CsvMapper();
mapper.findAndRegisterModules();
mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);

完成后，您的预期结果应该类似于:

finish,start
2020-01-16,2020-01-15
2020-01-17,2020-01-16
2020-01-18,2020-01-17
2020-01-19,2020-01-18
2020-01-20,2020-01-19