Add documentation for Hibernate example

Author: felipe-gdr

hibernate-example/readme.md

@@ -1,15 +1,14 @@
-# graphql-java-http-example
+# graphql-java-hibernate-example
 
-An example of using graphql-java in a HTTP application.
+An example of a simple graphql-java implementation backed by a Hibernate repository (via Spring Data JPA) and
+integrated with Spring Boot.
 
-It demonstrates the use of `Schema Definition Language (SDL)` to define a schema in a textual way.
- 
-It also shows how to use `data loader` to ensure that most efficient way to load
-inside a graphql query
+It shows how data fetchers can use Hibernate repositories to query the database.
 
-Finally it shows how to combine graphql-java `Instrumentation` to create performance tracing
-and data loader effectiveness statistics.
+In memory H2 is being used as the database, SQL scripts are execute during startup to add some sample data to
+the database. You can find those scripts in [data.sql](src/resources/data.sql).
 
+# Running the example
 To build the code type
 
     ./gradlew build

hibernate-example/src/main/java/com/graphql/java/hibernate/example/StarWarsWiring.java

@@ -14,9 +14,14 @@
 
 /**
  * This is our wiring used to put fetching behaviour behind a graphql field.
+ *
+ * Data fetchers declared here use {@link CharacterRepository} to query data from the database.
  */
 @Component
 public class StarWarsWiring {
+    /**
+     * The autowired {@link CharacterRepository}, that will be used by the data fetcher to access the database.
+     */
     private final CharacterRepository characterRepository;
 
     @Autowired
@@ -28,18 +33,30 @@ private CharacterRepository getCharacterRepository() {
         return characterRepository;
     }
 
+    /**
+     * Fetches one record from the database based on the type and id.
+     *
+     */
     DataFetcher humanDataFetcher = environment -> {
         String id = environment.getArgument("id");
 
         return getCharacterRepository().findByTypeAndId(Human.class, Long.valueOf(id));
     };
 
+    /**
+     * Fetches one record from the database based on the type and id.
+     */
     DataFetcher droidDataFetcher = environment -> {
         String id = environment.getArgument("id");
 
         return getCharacterRepository().findByTypeAndId(Droid.class, Long.valueOf(id));
     };
 
+    /**
+     * Fetches all characters that are associated with a given episode or a list of all characters if episode is not
+     * specified.
+     *
+     */
     DataFetcher charactersDataFetcher = environment -> {
         Episode episode = environment.getArgument("episode");
 
@@ -48,6 +65,9 @@ private CharacterRepository getCharacterRepository() {
                 getCharacterRepository().findByEpisode(episode);
     };
 
+    /**
+     * Fetches a list of friends of a given character.
+     */
     DataFetcher friendsDataFetcher = environment -> {
         FilmCharacter character = environment.getSource();
 

hibernate-example/src/main/java/com/graphql/java/hibernate/example/data/model/FilmCharacter.java

@@ -24,6 +24,9 @@ public abstract class FilmCharacter {
 
     private String name;
 
+    /**
+     * Eagerly fetches a list of friends ids.
+     */
     @ElementCollection(fetch = FetchType.EAGER)
     @CollectionTable(name = "CharacterFriend",
             joinColumns = @JoinColumn(name = "CharacterId"))

hibernate-example/src/main/java/com/graphql/java/hibernate/example/data/package-info.java

@@ -0,0 +1,11 @@
+/**
+ * This package contains the Hibernate code - entities and repository.
+ *
+ * There's absolutely nothing GraphQL specific about anything in this package. It could very well be replace with
+ * other database library tools like QueryDSL, JDBC a NoSQL data repository, etc.
+ *
+ * Some might find that the entity relationship is not very trivial. We have an abstract entity `FilmCharacter` with
+ * two concrete implementations: `Droid` and `Human`. This is to make this example support the same Star Wars GraphQL
+ * Schema used on other examples in this repo.
+ */
+package com.graphql.java.hibernate.example.data;