Offer a way to retrieve the component type of a JavaClass that is an array

archunit/src/main/java/com/tngtech/archunit/core/domain/ImportContext.java

@@ -56,4 +56,6 @@ public interface ImportContext {
     Set<JavaConstructor> getConstructorsWithParameterOfType(JavaClass javaClass);
 
     Set<ThrowsDeclaration<JavaConstructor>> getConstructorThrowsDeclarationsOfType(JavaClass javaClass);
+
+    JavaClass resolveClass(String fullyQualifiedClassName);
 }

archunit/src/main/java/com/tngtech/archunit/core/domain/JavaClass.java

@@ -81,6 +81,7 @@ public class JavaClass implements HasName.AndFullName, HasAnnotations, HasModifi
     private final Set<JavaClass> interfaces = new HashSet<>();
     private final Set<JavaClass> subClasses = new HashSet<>();
     private Optional<JavaClass> enclosingClass = Optional.absent();
+    private Optional<JavaClass> componentType = Optional.absent();
     private Supplier<Map<String, JavaAnnotation>> annotations =
             Suppliers.ofInstance(Collections.<String, JavaAnnotation>emptyMap());
     private Supplier<Set<JavaMethod>> allMethods;
@@ -186,6 +187,30 @@ public boolean isArray() {
         return javaType.isArray();
     }
 
+    /**
+     * This is a convenience method for {@link #tryGetComponentType()} in cases where
+     * clients know that this type is certainly an array type and thus the component type present.
+     * @throws IllegalArgumentException if this class is no array
+     * @return The result of {@link #tryGetComponentType()}
+     */
+    @PublicAPI(usage = ACCESS)
+    public JavaClass getComponentType() {
+        return tryGetComponentType().getOrThrow(new IllegalArgumentException(
+                String.format("Type %s is no array", getSimpleName())));
+    }
+
+    /**
+     * Returns the component type of this class, if this class is an array, otherwise
+     * {@link Optional#absent()}. The component type is the type of the elements of an array type.
+     * Consider {@code String[]}, then the component type would be {@code String}.
+     * Likewise for {@code String[][]} the component type would be {@code String[]}.
+     * @return The component type, if this type is an array, otherwise {@link Optional#absent()}
+     */
+    @PublicAPI(usage = ACCESS)
+    Optional<JavaClass> tryGetComponentType() {
+        return componentType;
+    }
+
     /**
      * @return Returns true if this class is declared within another class.
      *         Returns false for top-level classes.
@@ -841,6 +866,7 @@ public Map<String, JavaAnnotation> get() {
     }
 
     CompletionProcess completeFrom(ImportContext context) {
+        completeComponentType(context);
         enclosingClass = context.createEnclosingClass(this);
         memberDependenciesOnClass = new MemberDependenciesOnClass(
                 context.getFieldsOfType(this),
@@ -852,6 +878,15 @@ CompletionProcess completeFrom(ImportContext context) {
         return new CompletionProcess();
     }
 
+    private void completeComponentType(ImportContext context) {
+        JavaClass current = this;
+        while (current.isArray() && !current.componentType.isPresent()) {
+            JavaClass componentType = context.resolveClass(current.javaType.tryGetComponentType().get().getName());
+            current.componentType = Optional.of(componentType);
+            current = componentType;
+        }
+    }
+
     @Override
     public String toString() {
         return "JavaClass{name='" + javaType.getName() + "\'}";

archunit/src/main/java/com/tngtech/archunit/core/importer/ClassGraphCreator.java

@@ -275,6 +275,11 @@ public Optional<JavaClass> createEnclosingClass(JavaClass owner) {
                 Optional.<JavaClass>absent();
     }
 
+    @Override
+    public JavaClass resolveClass(String fullyQualifiedClassName) {
+        return classes.getOrResolve(fullyQualifiedClassName);
+    }
+
     private static class MemberDependenciesByTarget {
         private final SetMultimap<JavaClass, JavaField> fieldTypeDependencies = HashMultimap.create();
         private final SetMultimap<JavaClass, JavaMethod> methodParameterTypeDependencies = HashMultimap.create();
@@ -336,4 +341,4 @@ Set<ThrowsDeclaration<JavaConstructor>> getConstructorThrowsDeclarationsOfType(J
             return constructorThrowsDeclarationDependencies.get(javaClass);
         }
     }
-}
+}

archunit/src/test/java/com/tngtech/archunit/core/domain/JavaClassTest.java

@@ -23,6 +23,9 @@
 import com.tngtech.archunit.core.domain.testobjects.IsArrayTestClass;
 import com.tngtech.archunit.core.domain.testobjects.SuperA;
 import com.tngtech.archunit.core.importer.ClassFileImporter;
+import com.tngtech.archunit.core.importer.testexamples.arrays.ClassAccessingOneDimensionalArray;
+import com.tngtech.archunit.core.importer.testexamples.arrays.ClassAccessingTwoDimensionalArray;
+import com.tngtech.archunit.core.importer.testexamples.arrays.ClassUsedInArray;
 import com.tngtech.java.junit.dataprovider.DataProvider;
 import com.tngtech.java.junit.dataprovider.DataProviderRunner;
 import com.tngtech.java.junit.dataprovider.UseDataProvider;
@@ -80,13 +83,49 @@ public void finds_array_type() {
         JavaMethod method = importClassWithContext(IsArrayTestClass.class).getMethod("anArray");
 
         assertThat(method.getRawReturnType().isArray()).isTrue();
+        assertThat(method.getRawReturnType().tryGetComponentType().get()).matches(Object.class);
     }
 
     @Test
     public void finds_non_array_type() {
         JavaMethod method = importClassWithContext(IsArrayTestClass.class).getMethod("notAnArray");
 
         assertThat(method.getRawReturnType().isArray()).isFalse();
+        assertThat(method.getRawReturnType().tryGetComponentType()).isAbsent();
+    }
+
+    @Test
+    public void finds_multidimensional_array_type() {
+        JavaClasses classes = importClassesWithContext(ClassUsedInArray.class, ClassAccessingOneDimensionalArray.class, ClassAccessingTwoDimensionalArray.class);
+        JavaClass type = classes.get(ClassUsedInArray.class);
+        JavaClass oneDimArray = classes.get(ClassAccessingOneDimensionalArray.class).getField("array").getRawType();
+        JavaClass twoDimArray = classes.get(ClassAccessingTwoDimensionalArray.class).getField("array").getRawType();
+
+        assertThat(oneDimArray.isArray()).isTrue();
+        assertThat(oneDimArray.tryGetComponentType().get()).isEqualTo(type);
+        assertThat(twoDimArray.isArray()).isTrue();
+        assertThat(twoDimArray.tryGetComponentType().get()).isEqualTo(oneDimArray);
+        assertThat(twoDimArray.tryGetComponentType().get().tryGetComponentType().get()).isEqualTo(type);
+    }
+
+    @Test
+    public void finds_component_type_chain_of_otherwise_unreferenced_component_type() {
+        class OnlyReferencingMultiDimArray {
+            OnlyReferencingMultiDimArray[][][] field;
+        }
+
+        JavaClass javaClass = importClassesWithContext(OnlyReferencingMultiDimArray.class)
+                .get(OnlyReferencingMultiDimArray.class);
+
+        JavaClass arrayType = javaClass.getField("field").getRawType();
+        JavaClass twoDim = arrayType.getComponentType();
+        assertThat(twoDim.getName()).isEqualTo(OnlyReferencingMultiDimArray[][].class.getName());
+
+        JavaClass oneDim = twoDim.getComponentType();
+        assertThat(oneDim.getName()).isEqualTo(OnlyReferencingMultiDimArray[].class.getName());
+
+        JavaClass original = oneDim.getComponentType();
+        assertThat(original).isEqualTo(javaClass);
     }
 
     @Test
@@ -1134,4 +1173,4 @@ private class NestedNamedInnerClass {
             }
         }
     }
-}
+}

archunit/src/test/java/com/tngtech/archunit/core/importer/ImportTestUtils.java

@@ -428,5 +428,10 @@ public Set<JavaConstructor> getConstructorsWithParameterOfType(JavaClass javaCla
         public Set<ThrowsDeclaration<JavaConstructor>> getConstructorThrowsDeclarationsOfType(JavaClass javaClass) {
             return Collections.emptySet();
         }
+
+        @Override
+        public JavaClass resolveClass(String fullyQualifiedClassName) {
+            throw new UnsupportedOperationException("Override me where necessary");
+        }
     }
-}
+}