Dynamic Collection Handler

In database application development, sometimes we need to query different collections based on various conditions. Mongo-Plus provides a dynamic collection handler CollectionNameHandler, which allows us to dynamically change the collection name in MongoDB statements at runtime. This is particularly useful for handling sharding logic.

CollectionNameHandler

• Interface for dynamic collection handling
• String dynamicCollectionName(ExecuteMethodEnum, Object[], MongoNamespace): Parameters correspond to the method enum, method arguments, and namespace.

Example

Implement the CollectionNameHandler interface, create a dynamic collection handler, and register it as a Bean. In this example, if the query parameter contains userName and its value is 张三, the collection name is changed to user_zhangsan.

@Component
public class CustomCollectionNameHandler implements CollectionNameHandler {
    @Override
    public String dynamicCollectionName(ExecuteMethodEnum executeMethodEnum, Object[] source, MongoNamespace namespace) {
        if (executeMethodEnum == ExecuteMethodEnum.QUERY) {
            // Convert parameters according to com.mongoplus.execute.Execute interface
            // For example, executeQuery(Bson, BasicDBObject, BasicDBObject, Class<T>, MongoCollection<Document>)
            // The 0th parameter type is Bson
            Bson bson = (Bson) source[0];
            BsonString userName = bson.toBsonDocument().getString("userName", new BsonString(""));
            // If userName == 张三
            if (userName.getValue().equals("张三")) {
                // Return new collection name: user_zhangsan
                return "user_zhangsan";
            }
        }
        // Return original collection name if conditions not met
        return namespace.getCollectionName();
    }
}