Work harder not smarter

Talk given at JavaForumNord 2023 first.

1. Work harder not smarter
2. me Gerrit Meier Staff Software Engineer @ Neo4j
3. Why? How am I supposed to work even harder?
4. Why? How am I supposed to work even harder? !Most examples are over-simplified!
5. User Movie Actor Rating
6. User Rating Movie Actor uuid createdAt / updatedAt / etc. name dob …. uuid createdAt / updatedAt / etc. title stars …. uuid createdAt / updatedAt / etc. title plot …. uuid createdAt / updatedAt / etc. name dob ….
7. User Rating Movie Actor uuid createdAt / updatedAt / etc. name dob …. uuid createdAt / updatedAt / etc. title stars …. uuid createdAt / updatedAt / etc. title plot …. uuid createdAt / updatedAt / etc. name dob ….
8. Inheritance
9. Inheritance User Rating Movie Actor name dob …. title stars …. title plot …. name dob …. Entity uuid createdAt / updatedAt / etc.
10. Inheritance User Rating Movie Actor name dob …. title stars …. title plot …. name dob …. Entity uuid createdAt / updatedAt / etc.
11. Inheritance User Rating Movie Actor name dob …. title stars …. title plot …. …. Entity …. Person uuid
12. Inheritance User Rating Movie Actor name dob …. title stars …. title plot …. …. Entity …. Person uuid
13. Inheritance Entity User Movie Rating Person Actor
14. Inheritance Entity User Movie Rating Person Actor
15. Inheritance Entity User Movie Rating Person Actor
16. Inheritance Entity User Movie Rating Person Actor
17. Inheritance Entity User Movie Rating Person Actor
18. Inheritance Entity User Movie Rating Person Actor
19. Actor Entity uuid createdAt title actors Movie
20. Lombok Actor @ToString class Movie Entity uuid createdAt title actors Movie
21. Lombok Actor @ToString class Movie Entity uuid createdAt title actors Movie Movie(title=The Matrix, actors=[Actor(internationalActive=true)])
22. Lombok Actor @ToString(callSuper = true) class Movie Entity uuid createdAt title actors Movie Movie(super= Entity(uuid=c1e3c57e-...-b73147a13bfa, createdAt=2023-09-05T10:26:31.305), title=The Matrix, actors=[Actor(dob=1982-03-14,name=Your next Superstar,internationalActive=true,...)])
23. User Movie Actor Rating
24. User Movie Actor Rating
25. Lombok Actor @ToString(callSuper = true) class Movie Entity uuid createdAt title actors Movie Exception in thread "main" java.lang.StackOverflowError at java.lang.AbstractStringBuilder.append(AbstractStringBuilde r.java:449) at java.lang.StringBuilder.append(StringBuilder.java:141) at com.example.domain.Entity.toString(Entity.java:11) at com.example.domain.Movie.toString(Movie.java:11) at java.lang.String.valueOf(String.java:2994) at java.lang.StringBuilder.append(StringBuilder.java:136) at java.util.AbstractCollection.toString(AbstractCollection.ja va:462) at java.lang.String.valueOf(String.java:2994) at
26. Entity User Movie Rating Person Actor
27. Lombok Jackson Mapping
28. Jackson Actor new ObjectMapper() .writeValueAsString(movie) Entity uuid createdAt title actors Movie Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: java.util.ArrayList[0]->com.example.domain.Movie["actors"]- >java.util.ArrayList[0]->com.example.domain.Actor["movies"] ->java.util.ArrayList[0]->com.example.domain.Movie["actors" ]->java.util.ArrayList[0]->com.example.domain.Actor["movies "]->java.util.ArrayList[0]->com.example.domain.Movie["actor s"]->java.util.ArrayList[0]->com.example.domain.Actor["movi es"]->java.util.ArrayList[0]->com.example.domain.Movie["act ors"]->java.util.ArrayList[0]->com.example.domain.Actor["mo vies"]->java.util.ArrayList[0]->com.example.domain.Movie["a ctors"]->java.util.ArrayList[0]->com.example.domain.Actor[" movies"]->java.util.ArrayList[0]->com.example.domain.Movie[ "actors"]->java.util.ArrayList[0]->com.example.domain.Actor
29. Jackson Actor class Actor { @JsonIgnore public List<Movie> movies; } Entity uuid createdAt title actors Movie {"uuid":"xxxx", "createdAt":[2023,9,5,11,0,58,264000000], "title":"The Matrix", "actors":[{"uuid":"yyyy", "createdAt":[2023,9,5,11,0,58,265000000], "name":"Your next Superstar", "dob":"1982-03-14", "internationalActive":true} ] }
30. Jackson Actor class Actor { @JsonIgnoreProperties("actors") public List<Movie> movies; } Entity uuid createdAt title actors Movie {"uuid":"xxxx", "createdAt":[2023,9,5,11,2,8,999000000], "title":"The Matrix", "actors":[{"uuid":"yyyy", "createdAt":[2023,9,5,11,2,9,1000000], "name":"Your next Superstar", "dob":"1982-03-14", "internationalActive":true, "movies":[{"uuid":"xxxx", "createdAt":[2023,9,5,11,2,8,999000000], "title":"The Matrix"} ] } ] }
31. User Movie Actor Rating
32. Data loading (e.g. JPA) User data
33. Data loading (e.g. JPA) User data Rating data and Movie data OneToMany Ratings
34. Data loading (e.g. JPA) User data Rating data Movie data OneToMany(fetch = FetchType.EAGER) Ratings
35. Data loading (e.g. JPA) User data Rating data Movie data OneToMany Ratings @Entity @NamedEntityGraph(name = "User.ratings", attributeNodes = @NamedAttributeNode("ratings") ) public class User { //... }
36. Data loading (e.g. JPA) User data Rating data Movie data OneToMany Ratings @Entity @NamedEntityGraph(name = "User.ratings", attributeNodes = @NamedAttributeNode("ratings") ) public class User { //... } @Repository public interface UserRepository extends JpaRepository<User, String> { @EntityGraph(value = "User.ratings") User findEagerById(String id); }
37. Data loading (e.g. JPA) User data Rating data Movie data OneToMany Ratings @Repository public interface UserRepository extends JpaRepository<User, String> { @EntityGraph(attributePaths = {"ratings"}) User findEagerById(String id); }
38. Data loading • Model your domain to cover all data needed • Read and understand the specifications of your persistence mapper • Use built-in mechanisms to load the data for your use-case • Don’t try to work against the mapper library ◦ Use lower abstractions or drivers
39. Writing readable code public List<String> getValue(Movie m) { String x = "|"; return m.getRelated().stream() .map(a -> { String v1 = a.getValue1(); String v2 = a.getValue2(); return v1 + x + v2; }) .collect(Collectors.toList()); }
40. Writing readable code public List<String> getValue(Movie movie) { String fieldSeparator = "|"; return movie.getActors().stream() .map(actor -> { String actorName = actor.getName(); String actorDob = actor.getDob(); return actorName + fieldSeparator + actorDob; }) .collect(Collectors.toList()); }
41. Writing readable code: Be explicit public void setTimeout(int timeout);
42. Writing readable code: Be explicit public void setTimeout(int timeout[In]Seconds);
43. Writing readable code: Avoid Utils-classes public class DomainUtils { public static Movie createMovieWithDefaults() { return new Movie( UUID.randomUUID().toString(), "<no title>", LocalDateTime.now()); } public static List<Movie> top5Movies(List<Movie> movies) { return movies.stream() .sorted((movie1, movie2) -> movie2.getAverageRating().compareTo(movie1.getAverageRating())) .limit(5) .collect(Collectors.toList()); } }
44. Writing readable code: Avoid Utils-classes public class Movie { public static Movie createDefault() { return new Movie( UUID.randomUUID().toString(), "<no title>", LocalDateTime.now()); } }
45. Writing readable code: Avoid Utils-classes public class Movies { public static List<Movie> top5Movies(List<Movie> movies) { return movies.stream() .sorted((movie1, movie2) -> movie2.getAverageRating().compareTo(movie1.getAverageRating())) .limit(5) .collect(Collectors.toList()); } }
46. Writing readable code: Nesting / Extraction public void update(Movie movie) throws Exception { if (!movie.hasMetadata()) { HttpResponse httpResponse = HttpClientBuilder.create().build().execute(new HttpGet("METADATA_URL")); switch (httpResponse.getStatusLine().getStatusCode()) { case 200: BufferedReader responseReader = new BufferedReader(new InputStreamReader(httpResponse.getEntity().getContent())); String response = responseReader.lines().collect(Collectors.joining()); // movie.set... // default } } if (!movie.hasImage()) { HttpResponse httpResponse = HttpClientBuilder.create().build().execute(new HttpGet("IMAGE_URL")); switch (httpResponse.getStatusLine().getStatusCode()) { case 200: BufferedReader responseReader = new BufferedReader(new InputStreamReader(httpResponse.getEntity().getContent())); String response = responseReader.lines().collect(Collectors.joining()); // movie.setImage(...) // default } }
47. public void update(Movie movie) throws Exception { if (!movie.hasMetadata()) { updateMetadata(); } if (!movie.hasImage()) { updateImage(); } } Writing readable code: Nesting / Extraction
48. Writing readable code: Inversion public String getOldestActor(Movie movie) { String oldestActorName; List<Actor> actors = movie.getActors(); if (actors != null) { Actor oldestActor = actors.stream() .sorted(Comparator.comparing(Person::getDob)) .findFirst().get(); oldestActorName = oldestActor.getName(); } else { oldestActorName = ""; } return oldestActorName; }
49. Writing readable code: Inversion public String getOldestActor(Movie movie) { List<Actor> actors = movie.getActors(); if (actors == null) { return ""; } Actor oldestActor = actors.stream() .sorted(Comparator.comparing(Person::getDob)) .findFirst().get(); return oldestActor.getName(); }
50. Meta
51. Have friendly exception messages • Answer some questions ◦ How did “we” get here? ◦ How can “we” mitigate the situation? ▪ Documentation/GH-Issues • Be empathetic • You can still be technical ◦ What information is needed to support the customer • Don’t be too verbose • NEVER throw “expected” exceptions
52. Create a good documentation • Have a dedicated technical writer ◦ Implicit testing of your application and the documentation state • Give the documentation to new team members ◦ Helps with onboarding and also shows lacks in the documentation • (if possible) share link to the open source repository ◦ Problems/misunderstandings can be filed as issues ◦ Customers and users can create PRs
53. Control and communicate your architecture • ArchUnit • API Guardian @API(status = API.Status.STABLE/INTERNAL) • jQAssistant
54. Yes, you can use Optional
55. Yes, you can use Optional, If you are not doing real time big data processing
56. RTFM
57. No seriously, RTFM again
58. RTFM again
59. Thanks