MongoDB Java 驱动：如何使用$cond算子？

Question

I've written the following MongoDB update query:

db.getCollection("product").update(
  {},
  [
    {
      $set: {
        availability: {
          $cond: [
            {
              $eq: ["$availability", true],
            },
            "Yes",
            "No",
          ],
        },
      },
    }
  ]
);

that updates all documents in product collection: set a new value for availability property based on its current value.

And I am trying to rewrite the query above for MongoDB Java driver:

db.getCollection("product")
     .updateMany(new BsonDocument(), Updates.set("available", "YES"));

but I am stuck with $cond operator, I don't know how to translate $cond operator from MongoDB query to Java driver.

Could you please suggest possible options?

Answer 1

You need to use different variation which requires ClientSession rather than MongoClient

UpdateResult updateResult = this.mongoColWrite.
                 updateMany(this.clientSession, new Document(), setUpdateList);

empty doc is the condition. You can add any condition there.

You have to provide the list for the update.

[
    {
      $set: {
        availability: {
          $cond: [
            {
              $eq: ["$availability", true],
            },
            "Yes",
            "No",
          ],
        },
      },
    }
  ]

LinkedList<Object> condList = new LinkedList<Object>();
LinkedList<Object> eqArray = new LinkedList<Object>();
eqArray.add("$availability");
eqArray.add(true); 
condList.add(new Document("$eq"), eqArray);
condList.add("Yes");
condList.add("No");

Document availDoc = new Document("$cond", condList)
Document setDoc = new Document("$set", availDoc);

LinkedList<Document> setUpdateList = new LinkedList<Document>();
setUpdateList.add(setDoc);

This is how I usually does. Every array is a list . Every object is a Document .

Example with older version