本文介绍了将BSON类型ObjectId转换为JSON(存储在Mongodb中)-Java的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧! 问题描述 29岁程序员,3月因学历无情被辞! new Gson()。toJson(new ObjectId()) 当我执行上述操作时,我得到的输出是 但其实我希望它是 这是通常的mongodb ID格式。什么是Java的这个更好的方法? 更新: 我的价值对象 import com.google.gson.annotations.SerializedName; import org.bson.types.ObjectId; public class TaskObject { @SerializedName(_ id) private ObjectId _id; @SerializedName(revNo) private int revNo; } 我试图用自定义_id将它存储到mongodb中 TaskObject taskObject = new TaskObject(); taskObject.set_id(new ObjectId()); TaskMongoDBClient.getInstance()。 persistNewTaskData(new Gson()。toJson(taskObject)); 存储在mongodb中的内容如下所示。But Actually I want it to be as which is the usual mongodb ID format. What is the preferable method in Java for this?Update:My value objectimport com.google.gson.annotations.SerializedName;import org.bson.types.ObjectId;public class TaskObject { @SerializedName("_id") private ObjectId _id; @SerializedName("revNo") private int revNo;}I am trying to store this to mongodb with a custom _idTaskObject taskObject = new TaskObject();taskObject.set_id(new ObjectId());TaskMongoDBClient.getInstance(). persistNewTaskData(new Gson().toJson(taskObject));What is stored in the mongodb looks like this.Instead of _id:{"$oid": xxxx} which i can query by using a the oid value.What I am doing wrong here? please help.Thanks 解决方案 There are at least two possible ways to do this. Probably the most correct way is to use the GSON TypeAdapter to configure how the ObjectId is written to (and read from) JSON. You need to create something that implements TypeAdapter and register it with the GsonBuilder, this way GSON knows there's a special way to handle ObjectIds.I've written a small test to prove this works, using your use case and example object (but omitted the revNo field for brevity):@Testpublic void shouldWriteCorrectJSON() { // given TaskObject taskObject = new TaskObject(); taskObject._id = new ObjectId("51eae100c2e6b6c222ec3431"); Gson gson = new GsonBuilder().registerTypeAdapter(ObjectId.class, new ObjectIdTypeAdapter()).create(); // when String gsonString = gson.toJson(taskObject); // then assertThat(gsonString, is("{\"_id\":{\"$oid\":\"51eae100c2e6b6c222ec3431\"}}"));}private class ObjectIdTypeAdapter extends TypeAdapter<ObjectId> { @Override public void write(final JsonWriter out, final ObjectId value) throws IOException { out.beginObject() .name("$oid") .value(value.toString()) .endObject(); } @Override public ObjectId read(final JsonReader in) throws IOException { in.beginObject(); assert "$oid".equals(in.nextName()); String objectId = in.nextString(); in.endObject(); return new ObjectId(objectId); }}Note that the test asserts the JSON looks the way you want it to, and that I had to create an ObjectIdTypeAdapter that knows the field name of ObjectId is "$oid" and the value is simply the string value of the ObjectID, and does not serialise all of the fields individually.Note also that if you change the way the object is written to JSON, you also need to change the way it's read. So I've also implemented read to check that the field name is the correct one (you should probably throw an Exception here instead of using a simple assert if it's not correct), and then read the value and create the ObjectId from this String value.In real life, you probably also want to check for null values in both of those cases too.Because I'm a responsible coder, I also wrote a test to show the reading case works too:@Testpublic void shouldReadFromJSON() { // given Gson gson = new GsonBuilder().registerTypeAdapter(ObjectId.class, new ObjectIdTypeAdapter()).create(); // when TaskObject actualTaskObject = gson.fromJson("{\"_id\":{\"$oid\":\"51eae100c2e6b6c222ec3431\"}}", TaskObject.class); // then TaskObject taskObject = new TaskObject(); taskObject._id = new ObjectId("51eae100c2e6b6c222ec3431"); assertThat(actualTaskObject._id, is(taskObject._id));}Further reading:TypeAdapterGsonBuilder.registerTypeAdapterJsonReader and JsonWriter 这篇关于将BSON类型ObjectId转换为JSON(存储在Mongodb中)-Java的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持! 上岸,阿里云!