BAEL-2779 Guide to classgraph library

libraries/pom.xml

@@ -699,6 +699,12 @@
 			<version>${reflections.version}</version>
 		</dependency>
 
+        <dependency>
+            <groupId>io.github.classgraph</groupId>
+            <artifactId>classgraph</artifactId>
+            <version>${classgraph.version}</version>
+        </dependency>
+
     </dependencies>
 
     <repositories>
@@ -916,6 +922,7 @@
         <mockftpserver.version>2.7.1</mockftpserver.version>
         <commons-net.version>3.6</commons-net.version>
         <reflections.version>0.9.11</reflections.version>
+        <classgraph.version>4.8.22</classgraph.version>
 
     </properties>
 

libraries/src/test/java/com/baeldung/classgraph/ClassGraphUnitTest.java

@@ -0,0 +1,78 @@
+package com.baeldung.classgraph;
+
+import io.github.classgraph.*;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Consumer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ClassGraphUnitTest {
+
+    @Test
+    public void whenClassAnnotationFilterIsDefined_thenTargetClassesCanBeFound() {
+        doTest(result -> {
+            ClassInfoList classInfos = result.getClassesWithAnnotation(TestAnnotation.class.getName());
+            assertThat(classInfos).extracting(ClassInfo::getName).contains(ClassWithAnnotation.class.getName());
+        });
+    }
+
+    @Test
+    public void whenMethodAnnotationFilterIsDefined_thenTargetClassesCanBeFound() {
+        doTest(result -> {
+            ClassInfoList classInfos = result.getClassesWithMethodAnnotation(TestAnnotation.class.getName());
+            assertThat(classInfos).extracting(ClassInfo::getName).contains(MethodWithAnnotation.class.getName());
+        });
+    }
+
+    @Test
+    public void whenMethodAnnotationValueFilterIsDefined_thenTargetClassesCanBeFound() {
+        doTest(result -> {
+            ClassInfoList classInfos = result.getClassesWithMethodAnnotation(TestAnnotation.class.getName());
+            ClassInfoList filteredClassInfos = classInfos.filter(classInfo -> {
+                return classInfo.getMethodInfo().stream().anyMatch(methodInfo -> {
+                    AnnotationInfo annotationInfo = methodInfo.getAnnotationInfo(TestAnnotation.class.getName());
+                    if (annotationInfo == null) {
+                        return false;
+                    }
+
+                    return "web".equals(annotationInfo.getParameterValues().getValue("value"));
+                });
+            });
+            assertThat(filteredClassInfos)
+                    .extracting(ClassInfo::getName)
+                    .contains(MethodWithAnnotationParameterWeb.class.getName());
+        });
+    }
+
+    @Test
+    public void whenFieldAnnotationFilterIsDefined_thenTargetClassesCanBeFound() {
+        doTest(result -> {
+            ClassInfoList classInfos = result.getClassesWithFieldAnnotation(TestAnnotation.class.getName());
+            assertThat(classInfos).extracting(ClassInfo::getName).contains(FieldWithAnnotation.class.getName());
+        });
+    }
+
+    @Test
+    public void whenResourceIsUsed_thenItCanBeFoundAndLoaded() throws IOException {
+        try (ScanResult result = new ClassGraph().whitelistPaths("classgraph").scan()) {
+            ResourceList resources = result.getResourcesWithExtension("config");
+            assertThat(resources).extracting(Resource::getPath).containsOnly("classgraph/my.config");
+            assertThat(resources.get(0).getContentAsString()).isEqualTo("my data");
+        }
+    }
+
+    private void doTest(Consumer<ScanResult> checker) {
+        try (ScanResult result = new ClassGraph().enableAllInfo()
+                                                 .whitelistPackages(getClass().getPackage().getName())
+                                                 .scan())
+        {
+            checker.accept(result);
+        }
+    }
+}

libraries/src/test/java/com/baeldung/classgraph/ClassWithAnnotation.java

@@ -0,0 +1,5 @@
+package com.baeldung.classgraph;
+
+@TestAnnotation
+public class ClassWithAnnotation {
+}

libraries/src/test/java/com/baeldung/classgraph/FieldWithAnnotation.java

@@ -0,0 +1,7 @@
+package com.baeldung.classgraph;
+
+public class FieldWithAnnotation {
+
+    @TestAnnotation
+    private String s;
+}

libraries/src/test/java/com/baeldung/classgraph/MethodWithAnnotation.java

@@ -0,0 +1,8 @@
+package com.baeldung.classgraph;
+
+public class MethodWithAnnotation {
+
+    @TestAnnotation
+    public void service() {
+    }
+}

libraries/src/test/java/com/baeldung/classgraph/MethodWithAnnotationParameterDao.java

@@ -0,0 +1,8 @@
+package com.baeldung.classgraph;
+
+public class MethodWithAnnotationParameterDao {
+
+    @TestAnnotation("dao")
+    public void service() {
+    }
+}

libraries/src/test/java/com/baeldung/classgraph/MethodWithAnnotationParameterWeb.java

@@ -0,0 +1,8 @@
+package com.baeldung.classgraph;
+
+public class MethodWithAnnotationParameterWeb {
+
+    @TestAnnotation("web")
+    public void service() {
+    }
+}

libraries/src/test/java/com/baeldung/classgraph/TestAnnotation.java

@@ -0,0 +1,14 @@
+package com.baeldung.classgraph;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.*;
+
+@Target({TYPE, METHOD, FIELD})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface TestAnnotation {
+
+    String value() default "";
+}

libraries/src/test/resources/classgraph/my.config

@@ -0,0 +1 @@
+my data