User Root Resource: Use CDI Provider for subresources.

Resources are request scoped and we need only one sub resource per
request. That is, injecting all subresources (and their transitive
inejctions)in the constructor builds a lot of objects that are never
used.

Solution: Inject provider, that lazily inject the needed subresources
on demand.

scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserRootResource.java

@@ -2,28 +2,30 @@ package sonia.scm.api.v2.resources;
 
 import com.google.inject.Inject;
 
+import javax.inject.Provider;
 import javax.ws.rs.Path;
 
 @Path(UserRootResource.USERS_PATH_V2)
 public class UserRootResource {
 
   public static final String USERS_PATH_V2 = "v2/users/";
-  private final UserCollectionResource userCollectionResource;
-  private final UserResource userResource;
+  private final Provider<UserCollectionResource> userCollectionResource;
+  private final Provider<UserResource> userResource;
 
   @Inject
-  public UserRootResource(UserCollectionResource userCollectionResource, UserResource userResource) {
+  public UserRootResource(Provider<UserCollectionResource> userCollectionResource,
+                          Provider<UserResource> userResource) {
     this.userCollectionResource = userCollectionResource;
     this.userResource = userResource;
   }
 
   @Path("")
   public UserCollectionResource getUserCollectionResource() {
-    return userCollectionResource;
+    return userCollectionResource.get();
   }
 
   @Path("{id}")
   public UserResource getUserResource() {
-    return userResource;
+    return userResource.get();
   }
 }

scm-webapp/src/test/java/sonia/scm/api/v2/resources/MockProvider.java

@@ -0,0 +1,22 @@
+package sonia.scm.api.v2.resources;
+
+import javax.inject.Provider;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * A mockito implementation of CDI {@link javax.inject.Provider}.
+ */
+class MockProvider {
+
+  private MockProvider() {}
+
+  static <I> Provider<I> of(I instance) {
+    @SuppressWarnings("unchecked") // Can't make mockito return typed provider
+    Provider<I> provider = mock(Provider.class);
+    when(provider.get()).thenReturn(instance);
+    return provider;
+  }
+
+}

scm-webapp/src/test/java/sonia/scm/api/v2/resources/UserRootResourceTest.java

@@ -64,8 +64,6 @@ public class UserRootResourceTest {
   @InjectMocks
   private UserToUserDtoMapperImpl userToDtoMapper;
 
-  private UserCollectionToDtoMapper userCollectionToDtoMapper;
-
   private ArgumentCaptor<User> userCaptor = ArgumentCaptor.forClass(User.class);
 
   @Before
@@ -76,10 +74,11 @@ public class UserRootResourceTest {
     when(userManager.get("Neo")).thenReturn(dummyUser);
     doNothing().when(userManager).create(userCaptor.capture());
 
-    userCollectionToDtoMapper = new UserCollectionToDtoMapper(userToDtoMapper, uriInfoStore);
-    UserCollectionResource userCollectionResource = new UserCollectionResource(userManager, dtoToUserMapper, userToDtoMapper, userCollectionToDtoMapper);
+    UserCollectionToDtoMapper userCollectionToDtoMapper = new UserCollectionToDtoMapper(userToDtoMapper, uriInfoStore);
+    UserCollectionResource userCollectionResource = new UserCollectionResource(userManager, dtoToUserMapper, userToDtoMapper,
+                                                                               userCollectionToDtoMapper);
     UserResource userResource = new UserResource(dtoToUserMapper, userToDtoMapper, userManager);
-    UserRootResource userRootResource = new UserRootResource(userCollectionResource, userResource);
+    UserRootResource userRootResource = new UserRootResource(MockProvider.of(userCollectionResource), MockProvider.of(userResource));
 
     dispatcher.getRegistry().addSingletonResource(userRootResource);
     when(uriInfo.getBaseUri()).thenReturn(URI.create("/"));