Let JarFileLocation work with custom ClassLoader URIs (#1131)

Some `ClassLoader`s that work with repackaged JAR files return custom resource URIs to indicate custom class loading locations. For example, the `ClassLoader` in a packaged Spring Boot app returns the following URI for source package named example: `jar:file:/Path/to/my.jar!/BOOT-INF/classes!/example/`. Note the second "!/" to indicate a classpath root.

Prior to this commit, `JarFileLocation` was splitting paths to a resource at the first "!/" assuming the remainder of the string would depict the actual resource path. That remainder potentially containing a further "!/" would prevent the JAR entry matching in `FromJar.classFilesBeneath(…)` as the entries themselves do not contain the exclamation mark.

This changes the treatment of the URI in `JarFileLocation` to rather use the *last* "!/" as splitting point so that the remainder is a proper path within the `ClassLoader` and the matching in `FromJar.classFilesBeneath(…)` works properly.

Note that in composition with custom `ClassLoader`s frameworks like Spring Boot can also install custom URL handling. In this case ArchUnit can read a class file from a nested archive URL like `jar:file:/some/file.jar!/BOOT-INF/classes!/...` using the standard `URL#openStream()` method in a completely transparent way (compare setup in `SpringLocationsTest`).

archunit-3rd-party-test/build.gradle

@@ -0,0 +1,16 @@
+plugins {
+    id 'archunit.java-conventions'
+}
+
+ext.moduleName = 'com.tngtech.archunit.thirdpartytest'
+
+dependencies {
+    testImplementation project(path: ':archunit', configuration: 'shadow')
+    testImplementation project(path: ':archunit', configuration: 'tests')
+    testImplementation dependency.springBootLoader
+    dependency.addGuava { dependencyNotation, config -> testImplementation(dependencyNotation, config) }
+    testImplementation dependency.log4j_slf4j
+    testImplementation dependency.junit4
+    testImplementation dependency.junit_dataprovider
+    testImplementation dependency.assertj
+}

archunit-3rd-party-test/src/test/java/com/tngtech/archunit/core/importer/SpringLocationsTest.java

@@ -0,0 +1,96 @@
+package com.tngtech.archunit.core.importer;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.function.Function;
+import java.util.jar.JarFile;
+import java.util.stream.Stream;
+
+import com.tngtech.archunit.core.importer.testexamples.SomeEnum;
+import com.tngtech.archunit.testutil.SystemPropertiesRule;
+import com.tngtech.java.junit.dataprovider.DataProvider;
+import com.tngtech.java.junit.dataprovider.DataProviderRunner;
+import com.tngtech.java.junit.dataprovider.UseDataProvider;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.loader.LaunchedURLClassLoader;
+import org.springframework.boot.loader.archive.Archive;
+import org.springframework.boot.loader.archive.JarFileArchive;
+
+import static com.google.common.collect.Iterators.getOnlyElement;
+import static com.google.common.collect.MoreCollectors.onlyElement;
+import static com.google.common.collect.Streams.stream;
+import static com.google.common.io.ByteStreams.toByteArray;
+import static com.tngtech.archunit.core.importer.LocationTest.classFileEntry;
+import static com.tngtech.archunit.core.importer.LocationTest.urlOfClass;
+import static com.tngtech.archunit.core.importer.LocationsTest.unchecked;
+import static com.tngtech.java.junit.dataprovider.DataProviders.testForEach;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@RunWith(DataProviderRunner.class)
+public class SpringLocationsTest {
+    /**
+     * Spring Boot configures some system properties that we want to reset afterward (e.g. custom URL stream handler)
+     */
+    @Rule
+    public final SystemPropertiesRule systemPropertiesRule = new SystemPropertiesRule();
+
+    @DataProvider
+    public static Object[][] springBootJars() {
+        Function<Function<TestJarFile, TestJarFile>, TestJarFile> createSpringBootJar = setUpJarFile -> setUpJarFile.apply(new TestJarFile())
+                .withNestedClassFilesDirectory("BOOT-INF/classes")
+                .withEntry(classFileEntry(SomeEnum.class).toAbsolutePath());
+
+        return testForEach(
+                createSpringBootJar.apply(TestJarFile::withDirectoryEntries),
+                createSpringBootJar.apply(TestJarFile::withoutDirectoryEntries)
+        );
+    }
+
+    @Test
+    @UseDataProvider("springBootJars")
+    public void finds_locations_of_packages_from_Spring_Boot_ClassLoader_for_JARs(TestJarFile jarFileToTest) throws Exception {
+        try (JarFile jarFile = jarFileToTest.create()) {
+
+            configureSpringBootContextClassLoaderKnowingOnly(jarFile);
+
+            String jarUri = new File(jarFile.getName()).toURI().toString();
+            Location location = Locations.ofPackage(SomeEnum.class.getPackage().getName()).stream()
+                    .filter(it -> it.contains(jarUri))
+                    .collect(onlyElement());
+
+            byte[] expectedClassContent = toByteArray(urlOfClass(SomeEnum.class).openStream());
+            Stream<byte[]> actualClassContents = stream(location.asClassFileSource(new ImportOptions()))
+                    .map(it -> unchecked(() -> toByteArray(it.openStream())));
+
+            boolean containsExpectedContent = actualClassContents.anyMatch(it -> Arrays.equals(it, expectedClassContent));
+            assertThat(containsExpectedContent)
+                    .as("one of the found class files has the expected class file content")
+                    .isTrue();
+        }
+    }
+
+    private static void configureSpringBootContextClassLoaderKnowingOnly(JarFile jarFile) throws IOException {
+        // This hooks in Spring Boot's own JAR URL protocol handler which knows how to handle URLs with
+        // multiple separators (e.g. "jar:file:/dir/some.jar!/BOOT-INF/classes!/pkg/some.class")
+        org.springframework.boot.loader.jar.JarFile.registerUrlProtocolHandler();
+
+        try (JarFileArchive jarFileArchive = new JarFileArchive(new File(jarFile.getName()))) {
+            JarFileArchive bootInfClassArchive = getNestedJarFileArchive(jarFileArchive, "BOOT-INF/classes/");
+
+            Thread.currentThread().setContextClassLoader(
+                    new LaunchedURLClassLoader(false, bootInfClassArchive, new URL[]{bootInfClassArchive.getUrl()}, null)
+            );
+        }
+    }
+
+    @SuppressWarnings("SameParameterValue")
+    private static JarFileArchive getNestedJarFileArchive(JarFileArchive jarFileArchive, String path) throws IOException {
+        Iterator<Archive> archiveCandidates = jarFileArchive.getNestedArchives(entry -> entry.getName().equals(path), entry -> true);
+        return (JarFileArchive) getOnlyElement(archiveCandidates);
+    }
+}

archunit/src/jdk9main/java/com/tngtech/archunit/core/importer/ModuleLocationResolver.java

@@ -34,9 +34,11 @@
 import static java.util.stream.Collectors.toList;
 
 class ModuleLocationResolver implements LocationResolver {
+    private final FromClasspathAndUrlClassLoaders standardResolver = new FromClasspathAndUrlClassLoaders();
+
     @Override
     public UrlSource resolveClassPath() {
-        Iterable<URL> classpath = UrlSource.From.classPathSystemProperties();
+        Iterable<URL> classpath = standardResolver.resolveClassPath();
         Set<ModuleReference> systemModuleReferences = ModuleFinder.ofSystem().findAll();
         Set<ModuleReference> configuredModuleReferences = ModuleFinder.of(modulepath()).findAll();
         Iterable<URL> modulepath = Stream.concat(systemModuleReferences.stream(), configuredModuleReferences.stream())

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

@@ -51,7 +51,7 @@ public void plugInLocationFactories(InitialConfiguration<Set<Location.Factory>>
 
             @Override
             public void plugInLocationResolver(InitialConfiguration<LocationResolver> locationResolver) {
-                locationResolver.set(new LocationResolver.Legacy());
+                locationResolver.set(new LocationResolver.FromClasspathAndUrlClassLoaders());
             }
         }
     }

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

@@ -17,6 +17,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.net.JarURLConnection;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
@@ -31,6 +32,7 @@
 import java.util.Enumeration;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.jar.JarEntry;
@@ -269,8 +271,8 @@ private static URI newJarUri(URI uri) {
         @Override
         ClassFileSource asClassFileSource(ImportOptions importOptions) {
             try {
-                String[] parts = uri.toString().split("!/", 2);
-                return new ClassFileSource.FromJar(new URL(parts[0] + "!/"), parts[1], importOptions);
+                ParsedUri parsedUri = ParsedUri.from(uri);
+                return new ClassFileSource.FromJar(new URL(parsedUri.base), parsedUri.path, importOptions);
             } catch (IOException e) {
                 throw new LocationException(e);
             }
@@ -288,28 +290,26 @@ public boolean isArchive() {
 
         @Override
         Collection<NormalizedResourceName> readResourceEntries() {
-            File file = getFileOfJar();
-            if (!file.exists()) {
-                return emptySet();
-            }
-
-            return readJarFileContent(file);
+            return getJarFile().map(this::readJarFileContent).orElse(emptySet());
         }
 
-        private File getFileOfJar() {
-            return new File(URI.create(uri.toString()
-                    .replaceAll("^" + SCHEME + ":", "")
-                    .replaceAll("!/.*", "")));
+        private Optional<JarFile> getJarFile() {
+            try {
+                // Note: We can't use a composed JAR URL like `jar:file:/path/to/file.jar!/com/example`, because opening the connection
+                //       fails with an exception if the directory entry for this path is missing (which is possible, even if there is
+                //       a class `com.example.SomeClass` in the JAR file).
+                String baseUri = ParsedUri.from(uri).base;
+                JarURLConnection jarUrlConnection = (JarURLConnection) new URL(baseUri).openConnection();
+                return Optional.of(jarUrlConnection.getJarFile());
+            } catch (IOException e) {
+                return Optional.empty();
+            }
         }
 
-        private Collection<NormalizedResourceName> readJarFileContent(File fileOfJar) {
+        private Collection<NormalizedResourceName> readJarFileContent(JarFile jarFile) {
             ImmutableList.Builder<NormalizedResourceName> result = ImmutableList.builder();
-            String prefix = uri.toString().replaceAll(".*!/", "");
-            try (JarFile jarFile = new JarFile(fileOfJar)) {
-                result.addAll(readEntries(prefix, jarFile));
-            } catch (IOException e) {
-                throw new LocationException(e);
-            }
+            String prefix = ParsedUri.from(uri).path;
+            result.addAll(readEntries(prefix, jarFile));
             return result.build();
         }
 
@@ -324,6 +324,22 @@ private List<NormalizedResourceName> readEntries(String prefix, JarFile jarFile)
             }
             return result;
         }
+
+        private static class ParsedUri {
+            final String base;
+            final String path;
+
+            private ParsedUri(String base, String path) {
+                this.base = base;
+                this.path = path;
+            }
+
+            static ParsedUri from(NormalizedUri uri) {
+                String uriString = uri.toString();
+                int entryPathStartIndex = uriString.lastIndexOf("!/") + 2;
+                return new ParsedUri(uriString.substring(0, entryPathStartIndex), uriString.substring(entryPathStartIndex));
+            }
+        }
     }
 
     private static class FilePathLocation extends Location {

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

@@ -28,7 +28,7 @@ interface LocationResolver {
     UrlSource resolveClassPath();
 
     @Internal
-    class Legacy implements LocationResolver {
+    class FromClasspathAndUrlClassLoaders implements LocationResolver {
         @Override
         public UrlSource resolveClassPath() {
             ImmutableList.Builder<URL> result = ImmutableList.builder();

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

@@ -173,12 +173,12 @@ private Path absolutePathOf(Class<?> clazz) throws URISyntaxException {
         return new File(urlOfClass(clazz).toURI()).getAbsoluteFile().toPath();
     }
 
-    private URI jarUriOfEntry(JarFile jarFile, String entry) {
+    static URI jarUriOfEntry(JarFile jarFile, String entry) {
         return jarUriOfEntry(jarFile, NormalizedResourceName.from(entry));
     }
 
-    private URI jarUriOfEntry(JarFile jarFile, NormalizedResourceName entry) {
-        return URI.create("jar:" + new File(jarFile.getName()).toURI().toString() + "!/" + entry);
+    private static URI jarUriOfEntry(JarFile jarFile, NormalizedResourceName entry) {
+        return URI.create("jar:" + new File(jarFile.getName()).toURI() + "!/" + entry);
     }
 
     @Test
@@ -342,7 +342,7 @@ private static InputStream streamOfClass(Class<?> clazz) {
         return clazz.getResourceAsStream(classFileResource(clazz));
     }
 
-    private static NormalizedResourceName classFileEntry(Class<?> clazz) {
+    static NormalizedResourceName classFileEntry(Class<?> clazz) {
         return NormalizedResourceName.from(classFileResource(clazz));
     }