In this post I’d like to show how to perform basic CRUD operations against a MongoDB database using the Java driver.
For this post, lets assume that we have a todo database with a collection of todo items. Each item has a task and a priority.
In terms of JSON notation, an example item would look like:
Now that we have defined what we are storing in the database, lets have a look at how we connect to Mongo.
Connection to the database
To connect to a MongoDB database, we would use code similar to that below. In this code you can see that we are connecting to a database called todo and getting the collection called items. In MongoDB if neither of these items exist, they will be automatically created.
To add a document to a collection, we use the insert() method of the collection.
To retrieve documents from a collection, we can create a query and then iterate through it with a cursor.
This query will find all the objects in the collection that have a priority of highest. If we wanted to get all of the items in the collection, we would create the cursor without a query as shown below.
To update an object, we first have to get the object from the collection then we save it back into the collection.
Finally, to delete a document or set of documents, we use the remove method of the collection.