The last remaining element on the Movie page is the list of ratings on the right-hand side of the page. Although the count in the header is now accurate, the ratings list being by the API needs to be implemented.
The list of ratings is populated by the forMovie() method in the RatingService, which currently returns a hardcoded list of ratings from the fixture ratings.json.
public List<Map<String,Object>> forMovie(String id, Params params) {
// TODO: Get ratings for a Movie
return AppUtils.process(ratings,params);
}In this challenge, you will run the following Cypher statement in a read transaction:
MATCH (u:User)-[r:RATED]->(m:Movie {tmdbId: $id})
RETURN r {
.rating,
.timestamp,
user: u {
.userId, .name
}
} AS review
ORDER BY r.timestamp DESC
SKIP $skip
LIMIT $limitYour Task
-
Modify the
forMovie()method to retrieve the ratings from Neo4j. -
Remember to auto-close the session and use the
toMap()function to convert the result record into native Java types.
Click to reveal the completed forMovie() method
public List<Map<String,Object>> forMovie(String id, Params params) {
// Open a new database session
try (var session = this.driver.session()) {
// Get ratings for a Movie
return session.executeRead(tx -> {
String query = String.format("""
MATCH (u:User)-[r:RATED]->(m:Movie {tmdbId: $id})
RETURN r {
.rating,
.timestamp,
user: u { .id, .name }
} AS review
ORDER BY r.`%s` %s
SKIP $skip
LIMIT $limit""", params.sort(Params.Sort.timestamp), params.order());
var res = tx.run(query, Values.parameters("id", id, "limit", params.limit(), "skip", params.skip()));
return res.list(row -> row.get("review").asMap());
});
}
}Testing
To test that this functionality has been correctly implemented, run the following code in a new terminal session:
mvn test -Dtest=neoflix._13_ListingRatingsTestThe test file is located at src/test/java/neoflix/_13_ListingRatingsTest.java.
Are you stuck? Click here for help
If you get stuck, you can see a working solution by checking out the 13-listing-ratings branch by running:
git checkout 13-listing-ratingsYou 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
Who was the first user to rate Pulp Fiction?
As part of the test suite, the final test will log the name of the first user to rate the movie Pulp Fiction.
Paste the name of the user the box below without quotes or whitespace and click Check Answer.
-
✓ Keith Howell
Hint
You can also find the answer by running the following Cypher statement:
MATCH (u:User)-[r:RATED]->(m:Movie {title: "Pulp Fiction"})
RETURN u.name
ORDER BY r.timestamp ASC
LIMIT 1Copy the answer without any quotes or whitespace.
Lesson Summary
In this Challenge, you modified the forMovie() method on the RatingService to return a paginated list of reviews for a movie from the Neo4j database.
In the next Challenge, you will update the PersonService to return list of actors and directors from Neo4j.