Add rule SpringBootRules.AllTypesInApplicationPackage

pom.xml

@@ -54,6 +54,12 @@
             <artifactId>spring-core</artifactId>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot</artifactId>
+            <scope>provided</scope>
+            <optional>true</optional>
+        </dependency>
 
         <dependency>
             <groupId>org.junit.jupiter</groupId>
@@ -78,6 +84,11 @@
             <artifactId>spring-web</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-autoconfigure</artifactId>
+            <scope>test</scope>
+        </dependency>
 
         <dependency>
             <groupId>org.slf4j</groupId>

src/main/java/de/rweisleder/archunit/spring/SpringBootRules.java

@@ -0,0 +1,72 @@
+package de.rweisleder.archunit.spring;
+
+import com.tngtech.archunit.core.domain.JavaClass;
+import com.tngtech.archunit.lang.ArchCondition;
+import com.tngtech.archunit.lang.ArchRule;
+import com.tngtech.archunit.lang.ConditionEvents;
+import com.tngtech.archunit.lang.conditions.ArchConditions;
+import org.springframework.boot.SpringBootConfiguration;
+
+import java.util.Collection;
+import java.util.List;
+
+import static com.tngtech.archunit.lang.conditions.ArchConditions.resideInAnyPackage;
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.classes;
+import static de.rweisleder.archunit.spring.MergedAnnotationPredicates.springAnnotatedWith;
+import static java.util.stream.Collectors.toList;
+
+/**
+ * Collection of {@link ArchRule rules} that can be used to check the structure of Spring Boot applications.
+ *
+ * @author Roland Weisleder
+ */
+public class SpringBootRules {
+
+    /**
+     * A rule that checks that all classes are located in the same package or a sub-package of the application class.
+     * The application class is the one annotated with {@code @SpringBootApplication} or {@code @SpringBootConfiguration}
+     * and must be within the given classes.
+     *
+     * @see #beInApplicationPackage()
+     */
+    public static final ArchRule AllTypesInApplicationPackage = classes()
+            .should(beInApplicationPackage())
+            .as("all types of a Spring Boot application should be located in the same package or a sub-package of the application class");
+
+    /**
+     * A condition that checks that the given classes are located in the same package or a sub-package of the application class.
+     * The application class is the one annotated with {@code @SpringBootApplication} or {@code @SpringBootConfiguration}
+     * and must be within the given classes.
+     * <p>
+     * In case the application class is not within the given classes, consider using {@link ArchConditions#resideInAnyPackage(String...)} directly.
+     *
+     * @see #AllTypesInApplicationPackage
+     */
+    public static ArchCondition<JavaClass> beInApplicationPackage() {
+        return new ArchCondition<JavaClass>("be located in the same package or a sub-package of the application class") {
+
+            private ArchCondition<JavaClass> inApplicationPackageCondition;
+
+            @Override
+            public void init(Collection<JavaClass> javaClasses) {
+                List<JavaClass> springBootApplicationClasses = javaClasses.stream()
+                        .filter(springAnnotatedWith(SpringBootConfiguration.class))
+                        .collect(toList());
+
+                if (springBootApplicationClasses.isEmpty()) {
+                    throw new AssertionError("Could not locate a class annotated with @SpringBootApplication or @SpringBootConfiguration");
+                }
+
+                String[] applicationPackageIdentifiers = springBootApplicationClasses.stream()
+                        .map(javaClass -> javaClass.getPackageName() + "..")
+                        .distinct().toArray(String[]::new);
+                inApplicationPackageCondition = resideInAnyPackage(applicationPackageIdentifiers);
+            }
+
+            @Override
+            public void check(JavaClass javaClass, ConditionEvents events) {
+                inApplicationPackageCondition.check(javaClass, events);
+            }
+        };
+    }
+}

src/test/java/de/rweisleder/archunit/spring/MergedAnnotationPredicatesTest.java

@@ -7,7 +7,6 @@
 import com.tngtech.archunit.core.domain.JavaMethod;
 import com.tngtech.archunit.core.domain.JavaParameter;
 import com.tngtech.archunit.core.domain.properties.CanBeAnnotated;
-import com.tngtech.archunit.core.importer.ClassFileImporter;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Lazy;
@@ -24,6 +23,7 @@
 
 import static com.tngtech.archunit.base.DescribedPredicate.describe;
 import static de.rweisleder.archunit.spring.MergedAnnotationPredicates.springAnnotatedWith;
+import static de.rweisleder.archunit.spring.TestUtils.importClass;
 import static org.assertj.core.api.Assertions.assertThat;
 
 class MergedAnnotationPredicatesTest {
@@ -236,10 +236,6 @@ void springAnnotatedWith_with_MergedAnnotations_predicate_rejects_non_matching_c
         assertThat(predicate).rejects(controllerClass);
     }
 
-    private JavaClass importClass(Class<?> classToImport) {
-        return new ClassFileImporter().importClass(classToImport);
-    }
-
     @Controller
     static class ControllerClass {
     }

src/test/java/de/rweisleder/archunit/spring/SpringBootRulesTest.java

@@ -0,0 +1,59 @@
+package de.rweisleder.archunit.spring;
+
+import com.tngtech.archunit.core.domain.JavaClasses;
+import com.tngtech.archunit.lang.EvaluationResult;
+import de.rweisleder.archunit.spring.testclasses.boot.app1.FirstSpringBootApplication;
+import de.rweisleder.archunit.spring.testclasses.boot.app1.subpackage.FirstAppClassInSubpackage;
+import de.rweisleder.archunit.spring.testclasses.boot.app2.SecondSpringBootApplication;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import static de.rweisleder.archunit.spring.TestUtils.importClasses;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class SpringBootRulesTest {
+
+    @Nested
+    class Rule_AllTypesInApplicationPackage {
+
+        @Test
+        void provides_a_description() {
+            String description = SpringBootRules.AllTypesInApplicationPackage.getDescription();
+            assertThat(description).isEqualTo("all types of a Spring Boot application should be located in the same package or a sub-package of the application class");
+        }
+
+        @Test
+        void has_no_violation_if_all_classes_are_in_application_package_or_subpackage() {
+            JavaClasses classes = importClasses(FirstSpringBootApplication.class, FirstAppClassInSubpackage.class);
+            EvaluationResult evaluationResult = SpringBootRules.AllTypesInApplicationPackage.evaluate(classes);
+            assertThat(evaluationResult.hasViolation()).isFalse();
+        }
+
+        @Test
+        void has_violation_for_class_outside_application_package() {
+            Class<?> classOutsideApplicationPackage = String.class;
+            JavaClasses classes = importClasses(FirstSpringBootApplication.class, classOutsideApplicationPackage);
+            EvaluationResult evaluationResult = SpringBootRules.AllTypesInApplicationPackage.evaluate(classes);
+            assertThat(evaluationResult.hasViolation()).isTrue();
+            assertThat(evaluationResult.getFailureReport().getDetails()).anySatisfy(detail -> {
+                assertThat(detail).contains(classOutsideApplicationPackage.getName(), "does not reside in any package");
+            });
+        }
+
+        @Test
+        void fails_if_classes_do_not_contain_a_Spring_Boot_application() {
+            JavaClasses classes = importClasses(String.class);
+            assertThatThrownBy(() -> SpringBootRules.AllTypesInApplicationPackage.evaluate(classes))
+                    .isInstanceOf(AssertionError.class)
+                    .hasMessageContaining("Could not locate a class annotated with @SpringBootApplication or @SpringBootConfiguration");
+        }
+
+        @Test
+        void has_no_violation_if_classes_contain_multiple_distinct_Spring_Boot_applications() {
+            JavaClasses classes = importClasses(FirstSpringBootApplication.class, SecondSpringBootApplication.class);
+            EvaluationResult evaluationResult = SpringBootRules.AllTypesInApplicationPackage.evaluate(classes);
+            assertThat(evaluationResult.hasViolation()).isFalse();
+        }
+    }
+}

src/test/java/de/rweisleder/archunit/spring/TestUtils.java

@@ -0,0 +1,16 @@
+package de.rweisleder.archunit.spring;
+
+import com.tngtech.archunit.core.domain.JavaClass;
+import com.tngtech.archunit.core.domain.JavaClasses;
+import com.tngtech.archunit.core.importer.ClassFileImporter;
+
+public class TestUtils {
+
+    public static JavaClasses importClasses(Class<?>... classes) {
+        return new ClassFileImporter().importClasses(classes);
+    }
+
+    public static JavaClass importClass(Class<?> classToImport) {
+        return new ClassFileImporter().importClass(classToImport);
+    }
+}

src/test/java/de/rweisleder/archunit/spring/testclasses/boot/app1/FirstSpringBootApplication.java

@@ -0,0 +1,7 @@
+package de.rweisleder.archunit.spring.testclasses.boot.app1;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class FirstSpringBootApplication {
+}

src/test/java/de/rweisleder/archunit/spring/testclasses/boot/app1/subpackage/FirstAppClassInSubpackage.java

@@ -0,0 +1,4 @@
+package de.rweisleder.archunit.spring.testclasses.boot.app1.subpackage;
+
+public class FirstAppClassInSubpackage {
+}

src/test/java/de/rweisleder/archunit/spring/testclasses/boot/app2/SecondSpringBootApplication.java

@@ -0,0 +1,7 @@
+package de.rweisleder.archunit.spring.testclasses.boot.app2;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SecondSpringBootApplication {
+}