使用MongoDB java驱动程序,在Document上应用toJson()方法将获得此文档的JSON表示,并将JsonMode设置为STRICT。 以下纪元格式用于日期:{" $ date" :" dateAsMilliseconds" }
使用mongoexport,我们获得ISO-8601格式。
见官方文件(https://docs.mongodb.com/manual/reference/mongodb-extended-json/):
在严格模式下,日期是ISO-8601日期格式,在模板YYYY-MM-DDTHH后面有一个强制时区字段:mm:ss.mmm< +/- Offset>。
< / LI>MongoDB JSON解析器目前不支持加载表示Unix纪元之前的日期的ISO-8601字符串。将早期时间日期和日期格式化为系统的time_t类型可以保存的日期和日期时,将使用以下格式: {&#34; $ date&#34; :{&#34; $ numberLong&#34; :&#34; dateAsMilliseconds&#34; }
如果有人能解释为什么MongoDB java驱动程序,mongoexport工具和官方文档之间没有使用通用格式,我将不胜感激?
感谢。
答案 0 :(得分:1)
显然, NO 有很好的理由让Java驱动程序偏离官方规范。唯一的例外是那些不能用ISO8601格式表达的日期(如B.C.日期......)
作为一种解决方法,我扩展了JsonWriter
类并提供了两个toJson
静态方法作为如何使用它的示例:
package whatever.package.you.like;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
import org.bson.BSONException;
import org.bson.BsonContextType;
import org.bson.BsonDocument;
import org.bson.codecs.BsonDocumentCodec;
import org.bson.codecs.EncoderContext;
import org.bson.conversions.Bson;
import org.bson.json.JsonMode;
import org.bson.json.JsonWriter;
import org.bson.json.JsonWriterSettings;
import com.mongodb.MongoClient;
/**
* A {@link JsonWriter} extension that conforms to the "strict" JSON format
* specified by MongoDB for data/time values.
*
* The {@link JsonWriter} class provided in the MongoDB Java driver (version
* 3.2.2) does not conform to official MongoDB specification for strict mode
* JSON (see https://docs.mongodb.com/manual/reference/mongodb-extended-json/).
* This is specifically a problem with the date/time values which get filled
* with a milliseconds value (i.e. {$date: 309249234098}) instead of the ISO8601
* date/time (i.e. {$date: "2016-07-14T08:44:23.234Z"}) value which the
* specification calls for. This extension of {@link JsonWriter} conforms to the
* MongoDb specification in this regard.
*/
public class ConformingJsonWriter extends JsonWriter {
private final JsonWriterSettings settings;
private final Writer writer;
private boolean writingIndentedDateTime = false;
/**
* Creates a new instance which uses {@code writer} to write JSON to.
*
* @param writer
* the writer to write JSON to.
*/
public ConformingJsonWriter(final Writer writer) {
this(writer, new JsonWriterSettings());
}
/**
* Creates a new instance which uses {@code writer} to write JSON to and uses
* the given settings.
*
* @param writer
* the writer to write JSON to.
* @param settings
* the settings to apply to this writer.
*/
public ConformingJsonWriter(final Writer writer,
final JsonWriterSettings settings) {
super(writer, settings);
this.writer = writer;
this.settings = settings;
setContext(new Context(null, BsonContextType.TOP_LEVEL, ""));
}
private void writeIndentation(int skip) throws IOException {
for (Context context = getContext()
.getParentContext(); context != null; context = context
.getParentContext()) {
if (skip-- <= 0) {
writer.write(settings.getIndentCharacters());
}
}
}
private static String millisToIso8601(long millis) throws IOException {
SimpleDateFormat dateFormat = new SimpleDateFormat(
"yyyy-MM-dd\'T\'HH:mm:ss.SSS\'Z\'");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
return dateFormat.format(new Date(millis));
}
@Override
protected void doWriteDateTime(final long value) {
if ((settings.getOutputMode() == JsonMode.STRICT)
&& (value >= -59014396800000L && value <= 253399536000000L)) {
try {
writeStartDocument();
if (settings.isIndent()) {
writingIndentedDateTime = true;
writer.write(settings.getNewLineCharacters());
writeIndentation(0);
} else {
writer.write(" ");
}
writer.write("\"$date\" : ");
writer.write("\"");
writer.write(millisToIso8601(value));
writer.write("\"");
writeEndDocument();
writingIndentedDateTime = false;
} catch (IOException e) {
throw new BSONException("Wrapping IOException", e);
}
} else {
super.doWriteDateTime(value);
}
}
@Override
protected void doWriteEndDocument() {
if (writingIndentedDateTime) {
try {
writer.write(settings.getNewLineCharacters());
writeIndentation(1);
writer.write("}");
if (getContext()
.getContextType() == BsonContextType.SCOPE_DOCUMENT) {
setContext(getContext().getParentContext());
writeEndDocument();
} else {
setContext(getContext().getParentContext());
}
} catch (IOException e) {
throw new BSONException("Wrapping IOException", e);
}
} else {
super.doWriteEndDocument();
}
}
/**
* Take a {@link Bson} instance and convert it to "strict" JSON
* representation with no indentation (read, "NOT pretty printed").
*
* @param bson
* The {@link Bson} instance to convert
* @return The JSON representation.
*/
public static String toJson(Bson bson) {
return toJson(bson, new JsonWriterSettings());
}
/**
* Take a {@link Bson} instance and convert it to JSON representation.
*
* @param bson
* The {@link Bson} instance to convert
* @param writerSettings
* {@link JsonWriterSettings} that specify details about how the
* JSON output should look.
* @return The JSON representation.
*/
public static String toJson(Bson bson,
final JsonWriterSettings writerSettings) {
BsonDocumentCodec encoder = new BsonDocumentCodec();
ConformingJsonWriter writer = new ConformingJsonWriter(new StringWriter(),
writerSettings);
encoder.encode(writer,
bson.toBsonDocument(BsonDocument.class,
MongoClient.getDefaultCodecRegistry()),
EncoderContext.builder().isEncodingCollectibleDocument(true)
.build());
return writer.getWriter().toString();
}
}