无法在 Mongodb 中序列化 LocalDate

Question

我正在使用 java 8 java.time.LocalDate 来解析日期。

但试图将 LocalDate 对象插入到 mongodb。我在 java 驱动程序中遇到错误：

private def writeData(measure: DBCollection, installation: Int, date: String, dates: ListBuffer[LocalDate],
                    values: ListBuffer[BigDecimal], validated: Boolean, overwrite: Boolean) {
  val timeValues: BasicDBList = new BasicDBList
  var i = 0
  while ( i < dates.size )  {
    val obj: BasicDBObject = new BasicDBObject("time", dates(i))
    obj.put("value", values(i).toString())
    timeValues.add(obj)
    i += 1
  }
  if ( debug ) System.out.println("Storedata: " + timeValues.toString) <-- error here

错误日志：

java.lang.RuntimeException: json can't serialize type : class java.time.LocalDate at com.mongodb.util.ClassMapBasedObjectSerializer.serialize(ClassMapBasedObjectSerializer.java:77) at com.mongodb.util.JSONSerializers$MapSerializer.serialize(JSONSerializers.java:317) at com.mongodb.util.ClassMapBasedObjectSerializer.serialize(ClassMapBasedObjectSerializer.java:79) at com.mongodb.util.JSONSerializers$IterableSerializer.serialize(JSONSerializers.java:290) at com.mongodb.util.ClassMapBasedObjectSerializer.serialize(ClassMapBasedObjectSerializer.java:79) at com.mongodb.util.JSON.serialize(JSON.java:54) at com.mongodb.util.JSON.serialize(JSON.java:40) at com.mongodb.BasicDBList.toString(BasicDBList.java:38) at web.MeasureAccess.writeData(MeasureAccess.scala:203) at web.MeasureAccess.firstTime(MeasureAccess.scala:52) at web.MeasureAccess$.main(MeasureAccess.scala:262) at web.MeasureAccess.main(MeasureAccess.scala) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:483) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

我正在使用 mongo-java-driver-2.13.0-rc1.jar 斯卡拉 2.11.4 和 java 1.8.0_25

为了完整性。

Answer 1

As Oliver Gierke mentions here

尚不支持此数据类型。我希望这将很快可用。

Answer 2

不幸的是，MongoDB 驱动程序使用 java.util.Date 类型，请参阅文档 here

因此您必须先将 LocalDate 转换为 Date 实例，例如：

MongoClient mongoClient = new MongoClient("localhost", 27017);
DB db = mongoClient.getDB("test");
DBCollection coll = db.getCollection("testcol");

LocalDate ld = LocalDate.now();
Instant instant = ld.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant();
Date date = Date.from(instant);

BasicDBObject doc = new BasicDBObject("localdate", date);
coll.insert(doc);

我建议使用 Morphia or Jongo 之类的东西来包装 MongoDB 驱动程序，因为您可以注册全局映射器以隐式地即时执行这些转换，以便您可以使用 LocalDate 等, 在您的域模型中

Answer 3

对于遇到此问题的任何人，以下转换器将帮助他们朝着正确的方向开始。这个 TypeConverter 在 Date 和 LocalDateTime 之间转换（做出这种区分是因为 OP 特别询问了 LocalDate）。

将以下转换器添加到 Morphia，如下所示：

morphia.getMapper().getConverters().addConverter(new LocalDateTimeConverter());

这是转换器class:

public class LocalDateTimeConverter extends TypeConverter implements SimpleValueConverter {

    public LocalDateTimeConverter() {
        // TODO: Add other date/time supported classes here
        // Other java.time classes: LocalDate.class, LocalTime.class
        // Arrays: LocalDateTime[].class, etc
        super(LocalDateTime.class);
    }

    @Override
    public Object decode(Class<?> targetClass, Object fromDBObject, MappedField optionalExtraInfo) {
        if (fromDBObject == null) {
            return null;
        }

        if (fromDBObject instanceof Date) {
            return ((Date) fromDBObject).toInstant().atZone(ZoneOffset.systemDefault()).toLocalDateTime();
        }

        if (fromDBObject instanceof LocalDateTime) {
            return fromDBObject;
        }

        // TODO: decode other types

        throw new IllegalArgumentException(String.format("Cannot decode object of class: %s", fromDBObject.getClass().getName()));
    }

    @Override
    public Object encode(Object value, MappedField optionalExtraInfo) {
        if (value == null) {
            return null;
        }

        if (value instanceof Date) {
            return value;
        }

        if (value instanceof LocalDateTime) {
            ZonedDateTime zoned = ((LocalDateTime) value).atZone(ZoneOffset.systemDefault());
            return Date.from(zoned.toInstant());
        }

        // TODO: encode other types

        throw new IllegalArgumentException(String.format("Cannot encode object of class: %s", value.getClass().getName()));
    }
}

无法在 Mongodb 中序列化 LocalDate

Cannot serialize LocalDate in Mongodb

java

json

scala

mongodb