prevent using same classloader multiple times

scm-webapp/src/test/java/sonia/scm/plugin/UberClassLoaderTest.java

@@ -0,0 +1,74 @@
+package sonia.scm.plugin;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.io.Resources;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junitpioneer.jupiter.TempDirectory;
+
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@ExtendWith(TempDirectory.class)
+class UberClassLoaderTest {
+
+  private final URLClassLoader parentClassLoader = new URLClassLoader(new URL[0]);
+
+  @Test
+  void shouldOnlyUseClassloaderOnce(@TempDirectory.TempDir Path tempDir) throws IOException {
+    ClassLoader mailClassLoader = createClassLoader(tempDir, "plugin.txt", "mail");
+    ClassLoader reviewClassLoader = createClassLoader(mailClassLoader, tempDir, "plugin.txt", "review");
+
+    UberClassLoader uberClassLoader = new UberClassLoader(parentClassLoader, ImmutableSet.of(mailClassLoader, reviewClassLoader));
+    List<URL> resources = Collections.list(uberClassLoader.findResources("plugin.txt"));
+
+    assertThat(resources).hasSize(2);
+    assertThat(toContent(resources)).containsOnly("mail", "review");
+  }
+
+  @Test
+  void shouldReturnResourceFromEachPluginClassLoader(@TempDirectory.TempDir Path tempDir) throws IOException {
+    ClassLoader mailClassLoader = createClassLoader(tempDir, "scm.txt", "mail");
+    ClassLoader reviewClassLoader = createClassLoader(tempDir, "scm.txt", "review");
+
+    UberClassLoader uberClassLoader = new UberClassLoader(parentClassLoader, ImmutableSet.of(mailClassLoader, reviewClassLoader));
+    List<URL> resources = Collections.list(uberClassLoader.findResources("scm.txt"));
+    assertThat(toContent(resources)).containsOnly("mail", "review");
+  }
+
+  @SuppressWarnings("UnstableApiUsage")
+  private List<String> toContent(Iterable<URL> resources) throws IOException {
+    List<String> content = new ArrayList<>();
+    for (URL resource : resources) {
+      content.add(Resources.toString(resource, StandardCharsets.UTF_8));
+    }
+    return content;
+  }
+
+  private ClassLoader createClassLoader(Path tempDir, String resource, String value) throws IOException {
+    return createClassLoader(Thread.currentThread().getContextClassLoader(), tempDir, resource, value);
+  }
+
+  private ClassLoader createClassLoader(ClassLoader parent, Path tempDir, String resource, String value) throws IOException {
+    Path directory = tempDir.resolve(UUID.randomUUID().toString());
+    Files.createDirectory(directory);
+
+    Files.write(directory.resolve(resource), value.getBytes(StandardCharsets.UTF_8));
+
+    return new URLClassLoader(new URL[]{
+      directory.toUri().toURL()
+    }, parent);
+  }
+
+
+}