来自java的mongodb upsert：如何获取现有对象的_id？

I'm using the mongo-jackson-wrapper with java and MongoDB. I find an object by querying a field of mine (not the _id field), and then I need to know the _id field value, whether the net result was an update or an insert. However, I get an exception:

我正在使用带有java和MongoDB的mongo-jackson-wrapper。我通过查询我的一个字段（而不是_id字段）找到一个对象，然后我需要知道_id字段值，无论结果是更新还是插入。但是，我得到一个例外：

com.mongodb.MongoException: No objects to return
    at net.vz.mongodb.jackson.WriteResult.getSavedId(WriteResult.java:97)

The exception comes from the wrapper, not the MongoDB driver itself.

异常来自包装器，而不是MongoDB驱动程序本身。

WriteResult<EntityDocument, String> wr 
   = coll.update(DBQuery.is("corefEntityId", corefEntityId), up, true,  false);

What (if anything) is the right way to do this?

什么（如果有的话）是正确的方法吗？

1 个解决方案

#1

You need to use findAndModify and set returnNew to true

您需要使用findAndModify并将returnNew设置为true

You can view the JavaDoc

您可以查看JavaDoc

This code should do the trick but I haven't tested it.

这段代码应该可以做到，但我还没有测试过。

coll.findAndModify(DBQuery.is("corefEntityId", corefEntityId), null, null, false, up, true, false);

coll.findAndModify（DBQuery.is（“corefEntityId”，corefEntityId），null，null，false，up，true，false）;

#1