Implement plain java reflections recurcive classes search in specified package name.

Author: daggerok

src/test/java/com/github/daggerok/JavaReflectionPlainTest.java

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+package com.github.daggerok;
+
+import io.vavr.control.Try;
+import lombok.extern.slf4j.Slf4j;
+import lombok.val;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import javax.tools.FileObject;
+import javax.tools.JavaFileObject;
+import javax.tools.StandardLocation;
+import javax.tools.ToolProvider;
+import java.io.File;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@Slf4j
+@DisplayName("java plain reflection tests")
+class JavaReflectionPlainTest {
+
+  private static final Function<Throwable, RuntimeException> asRuntimeException = throwable -> {
+    log.error(throwable.getLocalizedMessage());
+    return new RuntimeException(throwable);
+  };
+
+  /*private static final Supplier<RuntimeException> andThenJustDie = () -> {
+    log.error("just dei...");
+    return new RuntimeException();
+  };*/
+
+  private static final Function<String, Collection<Class<?>>> findAllPackageClasses = basePackageName -> {
+
+    Locale locale = Locale.getDefault();
+    Charset charset = StandardCharsets.UTF_8;
+    val fileManager = ToolProvider.getSystemJavaCompiler()
+                                  .getStandardFileManager(/* diagnosticListener */ null, locale, charset);
+
+    StandardLocation location = StandardLocation.CLASS_PATH;
+    JavaFileObject.Kind kind = JavaFileObject.Kind.CLASS;
+    Set<JavaFileObject.Kind> kinds = Collections.singleton(kind);
+    val javaFileObjects = Try.of(() -> fileManager.list(location, basePackageName, kinds, /* recurse */ true))
+                             .getOrElseThrow(asRuntimeException);
+
+    String pathToPackageAndClass = basePackageName.replace(".", File.separator);
+    Function<String, String> mapToClassName = s -> {
+      String prefix = Arrays.stream(s.split(pathToPackageAndClass))
+                            .findFirst()
+                            .orElse("");
+                            //.orElseThrow(andThenJustDie);
+      return s.replaceFirst(prefix, "")
+              .replaceAll(File.separator, ".");
+    };
+
+    return StreamSupport.stream(javaFileObjects.spliterator(), /* parallel */ true)
+                        .filter(javaFileObject -> javaFileObject.getKind().equals(kind))
+                        .map(FileObject::getName)
+                        .map(fileObjectName -> fileObjectName.replace(".class", ""))
+                        .map(mapToClassName)
+                        .map(className -> Try.of(() -> Class.forName(className))
+                                             .getOrElseThrow(asRuntimeException))
+                        .collect(Collectors.toList());
+  };
+
+  @Test
+  void find_class_annotation() {
+    Collection<Class<?>> classes = findAllPackageClasses.apply(getClass().getPackage().getName());
+    assertThat(classes).hasSizeGreaterThan(4);
+    classes.stream().map(String::valueOf).forEach(log::info);
+  }
+}

src/test/java/com/github/daggerok/JupiterTest.java

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+package com.github.daggerok.plain;
+
+import com.github.daggerok.plain.annotations.MyAggregate;
+
+@MyAggregate
+public class MyRootAggregate {}

src/test/java/com/github/daggerok/plain/MyRootAggregate.java

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+package com.github.daggerok.plain.aggregates;
+
+import com.github.daggerok.plain.annotations.MyAggregate;
+
+@MyAggregate
+public class MySiblingAggregate {}

src/test/java/com/github/daggerok/plain/aggregates/MySiblingAggregate.java

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+package com.github.daggerok.plain.aggregates.child;
+
+import com.github.daggerok.plain.annotations.MyAggregate;
+
+@MyAggregate
+public class MyChildAggregate {}

src/test/java/com/github/daggerok/plain/aggregates/child/MyChildAggregate.java

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+package com.github.daggerok.plain.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface MyAggregate {}