This challenge has three parts:
The My Favorites Feature
Clicking the My Favorites link in the main navigation will take you to page which contains a list of Movies that you can want to revisit later.
When a logged in user hovers their mouse over a Movie on the website, a bookmark icon appears in the top left hand corner. Clicking this icon will either add or remove the Movie from the user’s Favorites list.
When adding a Movie to the list, a POST request it sent to the /api/favorites/{id} endpoint. When this happens, the following chain of events will occur:
-
The server directs the request to the route handler in
AccountRoutes, which verifies the user’s JWT token and stores it in the request, before handling the request -
The route handler uses an instance of the
FavoriteService. -
The
add()method is then called on theFavoriteServiceinstance with the user ID taken from the JWT token, and the ID of the movie that has been extracted from the request URL. -
It is then the responsibility of the
FavoriteServiceto persist this information and format a response.
Likewise, when it is clicked for a Movie that has already been favorited, a DELETE request is sent to the same URL, and the Movie is removed from the list.
When adding a Movie to a User’s Favorite list, a relationship is created between the User and Movie with the type HAS_FAVORITE.
Adding a Movie to My Favorites
For the first part of this challenge, modify the add() method to open a new database session, run the Cypher statement to create te relationship, close the session and return the movie details along with an additional favorite property.
1. Open the Session
Call the session() method on the Driver instance to open a new session:
Unresolved directive in lesson.adoc - include::{repository-raw}/main/src/main/java/example/Index.java[tag=session]2. Create the Relationship
In a write transaction, run a Cypher statement to create the HAS_FAVORITE relationship between the User and Movie nodes, with a createdAt property to represent when the relationship was created.
Click here to reveal the Cypher statement
Unresolved directive in lesson.adoc - include::{cypher-repository-raw}/main/cypher/2-interacting/9-user-favorites/creating-the-relationship.cypher[]Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag="create"]3. Does the Movie exist?
If no records are returned, you can safely assume that the either the User or Movie do not exist.
In this case, throw a ValidationException with an appropriate error message.
Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag="throw"]4. Return results
Then, finally return the movie value from the first record returned from the database.
Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag="return",indent=0]Working Solution
Click here to reveal the completed add() method
Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag=add]Removing a Movie from My Favorites
The second part of this challenge is to write the code to remove a movie from the My Favorites list.
The code for deleting the HAS_FAVORITE relationship will be similar, only the Cypher statement will change.
Instead of two separate MATCH clauses, we can instead attempt to find the pattern within a single clause.
If the relationship (with an variable of r) exists, we will delete it and then return the movie information with favorite set to false.
Unresolved directive in lesson.adoc - include::{cypher-repository-raw}/main/cypher/2-interacting/9-user-favorites/deleting-the-relationship.cypher[]Use the code from the add() method above to implement the remove() function.
If you get stuck, you can reveal the completed method below.
Working Solution
Click here to reveal the completed remove() method
Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag=remove]Listing My Favorites
Finally, the all() method in the FavoriteService currently returns a hardcoded list of Movies from the fixture popular.json.
Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag=all]Update this method to return a paginated list of movies that the user has added to their My Favorites list.
Click here to reveal the Cypher statement
Unresolved directive in lesson.adoc - include::{cypher-repository-raw}/main/cypher/2-interacting/9-user-favorites/listing-favorites.cypher[]In the query the method we should also add dynamic sorting and pagination, with the string substitution for the sorting like we did in other places.
You have already written similar code a few times, so try to implement this one on your own. If you get stuck, you can view the full solution below.
Click here to reveal the completed all() method
Unresolved directive in lesson.adoc - include::{repository-raw}/07-favorites-list/src/main/java/neoflix/services/FavoriteService.java[tag=all]Testing
To test that this functionality has been correctly implemented, run the following code in a new terminal session:
mvn test -Dtest=neoflix._07_FavoritesListTestThe test file is located at src/test/java/neoflix/_07_FavoritesListTest.java.
Are you stuck? Click here for help
If you get stuck, you can see a working solution by checking out the 07-favorites-list branch by running:
git checkout 07-favorites-listYou may have to commit or stash your changes before checking out this branch. You can also click here to expand the Support pane.
Verifying the Test
If the test has run successfully, a user with the email address graphacademy.favorite@neo4j.com will have added the movie Toy Story to their list of favorites.
Hint
You can run the following query to check for the user within the database.
If the shouldVerify value returns true, the verification should be successful.
Unresolved directive in questions/verify.adoc - include::{cypher-repository-raw}/main/cypher/2-interacting/9-user-favorites/verify-relationship-exists.cypher[]Solution
The following statement will mimic the behaviour of the test, merging a new :User node with the email address graphacademy.favorite@neo4j.com and ensuring that a node exists for the movie Toy Story.
The test then merges a :HAS_FAVORITE relationship between the user and movie nodes.
MERGE (u:User {userId: '9f965bf6-7e32-4afb-893f-756f502b2c2a'})
SET u.email = 'graphacademy.favorite@neo4j.com'
MERGE (m:Movie {tmdbId: '862'})
SET m.title = 'Toy Story'
MERGE (u)-[r:HAS_FAVORITE]->(m)
RETURN *Once you have run this statement, click Try again…* to complete the challenge.
Module Summary
In this Challenge, you have written the code to manage a HAS_FAVORITE relationship between a User and a Movie within a write transaction.
In the next Challenge, you will write code to execute multiple queries in the same transaction.