Retrieve app version without downloading

 - Instead of invoking `getResource` via the underlying LRUCleaningResourceLoader, construct the resource based on the schemes used in the URI
  - For maven resource, parse the co-ordinates and construct MavenResource with the appropriate MavenProperties (configured in the server)
   - Make sure to inject the maven properties

 - Remove `getResource` from AppRegistryService as we no longer need to download the resource at the registry
 - Use DefaultResourceLoader in AppRegistry for the use case where the `--uri` option is used to download the http resource when `registerAll`
 - The delegating resource loader is now used only when downloading the metadata resource at the AppRegistry

 - Add tests for resource version retrieval

Resolves spring-cloud#1843

spring-cloud-dataflow-registry/src/main/java/org/springframework/cloud/dataflow/registry/AbstractAppRegistryCommon.java

@@ -17,6 +17,7 @@
 import org.springframework.cloud.dataflow.core.ApplicationType;
 import org.springframework.cloud.dataflow.registry.domain.AppRegistration;
 import org.springframework.cloud.dataflow.registry.support.ResourceUtils;
+import org.springframework.cloud.deployer.resource.maven.MavenProperties;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.support.PropertiesLoaderUtils;
@@ -27,26 +28,30 @@
  * {@link AppRegistryCommon} implementation common for the Classic and the Skipper modes.
  * 
  * @author Christian Tzolov
+ * @author Ilayaperumal Gopinathan
  */
 public abstract class AbstractAppRegistryCommon implements AppRegistryCommon {
 
 	private static final Logger logger = LoggerFactory.getLogger(AbstractAppRegistryCommon.class);
 
 	public static final String METADATA_KEY_SUFFIX = "metadata";
 
-	private ResourceLoader resourceLoader;
+	protected ResourceLoader resourceLoader;
+
+	protected MavenProperties mavenProperties;
 
 	public AbstractAppRegistryCommon(ResourceLoader resourceLoader) {
 		this.resourceLoader = resourceLoader;
 	}
 
-	public ResourceLoader getResourceLoader() {
-		return this.resourceLoader;
+	public AbstractAppRegistryCommon(ResourceLoader resourceLoader, MavenProperties mavenProperties) {
+		this.resourceLoader = resourceLoader;
+		this.mavenProperties = mavenProperties;
 	}
 
 	@Override
 	public Resource getAppResource(AppRegistration appRegistration) {
-		return this.resourceLoader.getResource(appRegistration.getUri().toString());
+		return ResourceUtils.getResource(appRegistration.getUri().toString(), this.mavenProperties);
 	}
 
 	@Override
@@ -121,9 +126,7 @@ protected Stream<AppRegistration> toValidAppRegistration(Map.Entry<String, URI>
 
 	private String getVersionOrBroken(String uri) {
 		try {
-			Resource appResource = resourceLoader.getResource(uri);
-
-			return ResourceUtils.getResourceVersion(appResource);
+			return ResourceUtils.getResourceVersion(uri, this.mavenProperties);
 		}
 		catch (IllegalStateException ise) {
 			logger.warn("", ise);

spring-cloud-dataflow-registry/src/main/java/org/springframework/cloud/dataflow/registry/AppRegistry.java

@@ -31,6 +31,7 @@
 import org.springframework.cloud.dataflow.core.ApplicationType;
 import org.springframework.cloud.dataflow.registry.domain.AppRegistration;
 import org.springframework.cloud.dataflow.registry.support.NoSuchAppRegistrationException;
+import org.springframework.cloud.deployer.resource.maven.MavenProperties;
 import org.springframework.cloud.deployer.resource.registry.UriRegistry;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
@@ -66,8 +67,6 @@ public class AppRegistry extends AbstractAppRegistryCommon implements AppRegistr
 
 	private final UriRegistry uriRegistry;
 
-	private final ResourceLoader resourceLoader;
-
 	private static final Function<Map.Entry<Object, Object>, AbstractMap.SimpleImmutableEntry<String, URI>> toStringAndUriFUNC = kv -> {
 		try {
 			return new AbstractMap.SimpleImmutableEntry<>((String) kv.getKey(), new URI((String) kv.getValue()));
@@ -80,9 +79,14 @@ public class AppRegistry extends AbstractAppRegistryCommon implements AppRegistr
 	public AppRegistry(UriRegistry uriRegistry, ResourceLoader resourceLoader) {
 		super(resourceLoader);
 		Assert.notNull(uriRegistry, "'uriRegistry' must not be null");
+		this.uriRegistry = uriRegistry;
+	}
+
+	public AppRegistry(UriRegistry uriRegistry, ResourceLoader resourceLoader, MavenProperties mavenProperties) {
+		super(resourceLoader, mavenProperties);
+		Assert.notNull(uriRegistry, "'uriRegistry' must not be null");
 		Assert.notNull(resourceLoader, "'resourceLoader' must not be null");
 		this.uriRegistry = uriRegistry;
-		this.resourceLoader = resourceLoader;
 	}
 
 	public AppRegistration find(String name, ApplicationType type) {

spring-cloud-dataflow-registry/src/main/java/org/springframework/cloud/dataflow/registry/service/AppRegistryService.java

@@ -5,7 +5,6 @@
 import org.springframework.cloud.dataflow.core.ApplicationType;
 import org.springframework.cloud.dataflow.registry.AppRegistryCommon;
 import org.springframework.cloud.dataflow.registry.domain.AppRegistration;
-import org.springframework.core.io.Resource;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 
@@ -37,8 +36,6 @@ public interface AppRegistryService extends AppRegistryCommon {
 
 	void delete(String name, ApplicationType type, String version);
 
-	Resource getResource(String uri);
-
 	boolean appExist(String name, ApplicationType type, String version);
 
 	Page<AppRegistration> findAllByTypeAndNameIsLike(ApplicationType type, String name, Pageable pageable);

spring-cloud-dataflow-registry/src/main/java/org/springframework/cloud/dataflow/registry/service/DefaultAppRegistryService.java

@@ -27,6 +27,7 @@
 import org.springframework.cloud.dataflow.registry.domain.AppRegistration;
 import org.springframework.cloud.dataflow.registry.repository.AppRegistrationRepository;
 import org.springframework.cloud.dataflow.registry.support.NoSuchAppRegistrationException;
+import org.springframework.cloud.deployer.resource.maven.MavenProperties;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.data.domain.Page;
@@ -64,18 +65,13 @@ public class DefaultAppRegistryService extends AbstractAppRegistryCommon impleme
 	private final AppRegistrationRepository appRegistrationRepository;
 
 	public DefaultAppRegistryService(AppRegistrationRepository appRegistrationRepository,
-			ResourceLoader resourceLoader) {
-		super(resourceLoader);
+			ResourceLoader resourceLoader, MavenProperties mavenProperties) {
+		super(resourceLoader, mavenProperties);
 		Assert.notNull(appRegistrationRepository, "'appRegistrationRepository' must not be null");
 		Assert.notNull(resourceLoader, "'resourceLoader' must not be null");
 		this.appRegistrationRepository = appRegistrationRepository;
 	}
 
-	@Override
-	public Resource getResource(String uri) {
-		return (uri == null) ? null : this.getResourceLoader().getResource(uri);
-	}
-
 	@Override
 	public AppRegistration find(String name, ApplicationType type) {
 		return this.getDefaultApp(name, type);

spring-cloud-dataflow-registry/src/main/java/org/springframework/cloud/dataflow/registry/support/ResourceUtils.java

@@ -18,19 +18,25 @@
 import java.io.File;
 import java.io.IOException;
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.util.function.BiFunction;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import org.springframework.cloud.deployer.resource.docker.DockerResource;
+import org.springframework.cloud.deployer.resource.maven.MavenProperties;
 import org.springframework.cloud.deployer.resource.maven.MavenResource;
+import org.springframework.cloud.deployer.resource.support.DownloadingUrlResourceLoader;
+import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.UrlResource;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
  * @author Mark Pollack
+ * @author Ilayaperumal Gopinathan
  */
 public class ResourceUtils {
 
@@ -86,6 +92,44 @@ private static URI getUri(UrlResource urlResource) {
 		return uri;
 	}
 
+	/**
+	 * Retrieve the corresponding {@link Resource} instance based on the URI String.
+	 * Maven properties are used if the URI corresponds to maven resource.
+	 *
+	 * @param uriString String representation of the resource URI
+	 * @param mavenProperties the maven properties to use in case of maven resource
+	 * @return the resource instance
+	 */
+	public static Resource getResource(String uriString, MavenProperties mavenProperties) {
+		Assert.isTrue(StringUtils.hasText(uriString), "Resource URI must not be empty");
+		try {
+			URI uri = new URI(uriString);
+			String scheme = uri.getScheme();
+			Assert.notNull(scheme, "a scheme (prefix) is required");
+			if (scheme.equals("maven")) {
+				String coordinates = uriString.replaceFirst("maven:\\/*", "");
+				MavenResource mavenResource = MavenResource.parse(coordinates, mavenProperties);
+				return mavenResource;
+			}
+			else if (scheme.equals("docker")) {
+				return new DockerResource(uriString);
+			}
+			else {
+				ResourceLoader resourceLoader = null;
+				if (!scheme.equalsIgnoreCase("http") && !scheme.equalsIgnoreCase("https")) {
+					resourceLoader = new DefaultResourceLoader();
+				}
+				else {
+					resourceLoader = new DownloadingUrlResourceLoader();
+				}
+				return resourceLoader.getResource(uriString);
+			}
+		}
+		catch (URISyntaxException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
 	/**
 	 * Extracts the version from the resource. Supported resource types are {@link
 	 * MavenResource}, {@link DockerResource}, and {@link UrlResource}. @param resource to be
@@ -110,6 +154,17 @@ else if (resource instanceof UrlResource) {
 		}
 	}
 
+	/**
+	 * Returns the version for the given resource URI string.
+	 *
+	 * @param uriString String representation of the resource URI
+	 * @param mavenProperties the maven properties to use in case of maven resource
+	 * @return the resource version
+	 */
+	public static String getResourceVersion(String uriString, MavenProperties mavenProperties) {
+		return ResourceUtils.getResourceVersion(getResource(uriString, mavenProperties));
+	}
+
 	private static String formatDockerResource(DockerResource dockerResource,
 			BiFunction<String, Integer, String> function) {
 		try {

spring-cloud-dataflow-registry/src/test/java/org/springframework/cloud/dataflow/registry/support/ResourceUtilsTests.java

@@ -15,14 +15,18 @@
  */
 package org.springframework.cloud.dataflow.registry.support;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.fail;
-
 import java.net.MalformedURLException;
 
 import org.junit.Test;
+
+import org.springframework.cloud.deployer.resource.maven.MavenProperties;
+import org.springframework.cloud.deployer.resource.maven.MavenResource;
+import org.springframework.core.io.Resource;
 import org.springframework.core.io.UrlResource;
 
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
+
 /**
  * @author Mark Pollack
  * @author Ilayaperumal Gopinathan
@@ -115,6 +119,19 @@ public void testJars() throws MalformedURLException {
 		assertThat(version).isEqualTo("1.2.0-SNAPSHOT");
 		theRest = ResourceUtils.getResourceWithoutVersion(urlResource);
 		assertThat(theRest).isEqualTo("http://repo.spring.io/libs-release/org/springframework/cloud/stream/app/file-sink-rabbit/file-sink-rabbit");
+	}
+
+	@Test
+	public void testGetResource() {
+		String mavenUri = "maven://org.springframework.cloud.stream.app:aggregate-counter-sink-rabbit:1.3.0.RELEASE";
+		Resource resource = ResourceUtils.getResource(mavenUri, new MavenProperties());
+		assertThat(resource).isInstanceOf(MavenResource.class);
+	}
 
+	@Test
+	public void testGetResourceVersion() {
+		String mavenUri = "maven://org.springframework.cloud.stream.app:aggregate-counter-sink-rabbit:1.3.0.RELEASE";
+		String version = ResourceUtils.getResourceVersion(ResourceUtils.getResource(mavenUri, new MavenProperties()));
+		assertThat(version).isEqualTo("1.3.0.RELEASE");
 	}
 }

spring-cloud-dataflow-server-core/src/main/java/org/springframework/cloud/dataflow/server/config/DataFlowControllerAutoConfiguration.java

@@ -147,24 +147,25 @@ public UriRegistry uriRegistry(DataSource dataSource) {
 	@Bean
 	@ConditionalOnExpression("#{'${" + FeaturesProperties.FEATURES_PREFIX + "." + FeaturesProperties.SKIPPER_ENABLED
 			+ ":false}'.equalsIgnoreCase('false')}")
-	public AppRegistry appRegistry(UriRegistry uriRegistry, DelegatingResourceLoader resourceLoader) {
-		return new AppRegistry(uriRegistry, resourceLoader);
+	public AppRegistry appRegistry(UriRegistry uriRegistry, DelegatingResourceLoader resourceLoader,
+			MavenProperties mavenProperties) {
+		return new AppRegistry(uriRegistry, resourceLoader, mavenProperties);
 	}
 
 	@Bean
 	@ConditionalOnExpression("#{'${" + FeaturesProperties.FEATURES_PREFIX + "." + FeaturesProperties.SKIPPER_ENABLED
 			+ ":false}'.equalsIgnoreCase('true')}")
 	public AppRegistryService appRegistryService(AppRegistrationRepository appRegistrationRepository,
 			DelegatingResourceLoader resourceLoader) {
-		return new DefaultAppRegistryService(appRegistrationRepository, resourceLoader);
+		return new DefaultAppRegistryService(appRegistrationRepository, resourceLoader, mavenProperties());
 	}
 
 	@Bean
 	@ConditionalOnExpression("#{'${" + FeaturesProperties.FEATURES_PREFIX + "." + FeaturesProperties.SKIPPER_ENABLED
 			+ ":false}'.equalsIgnoreCase('true')}")
 	public VersionedAppRegistryController appRegistryController2(AppRegistryService appRegistry,
 			ApplicationConfigurationMetadataResolver metadataResolver) {
-		return new VersionedAppRegistryController(appRegistry, metadataResolver, appRegistryFJPFB().getObject());
+		return new VersionedAppRegistryController(appRegistry, metadataResolver, appRegistryFJPFB().getObject(), mavenProperties());
 	}
 
 	@Bean

spring-cloud-dataflow-server-core/src/main/java/org/springframework/cloud/dataflow/server/controller/VersionedAppRegistryController.java

@@ -40,8 +40,10 @@
 import org.springframework.cloud.dataflow.registry.support.ResourceUtils;
 import org.springframework.cloud.dataflow.rest.resource.AppRegistrationResource;
 import org.springframework.cloud.dataflow.rest.resource.DetailedAppRegistrationResource;
+import org.springframework.cloud.deployer.resource.maven.MavenProperties;
 import org.springframework.core.io.ByteArrayResource;
-import org.springframework.core.io.Resource;
+import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
@@ -85,12 +87,17 @@ public class VersionedAppRegistryController {
 
 	private ForkJoinPool forkJoinPool;
 
+	private final MavenProperties mavenProperties;
+
+	private ResourceLoader resourceLoader = new DefaultResourceLoader();
+
 	public VersionedAppRegistryController(AppRegistryService appRegistryService,
 			ApplicationConfigurationMetadataResolver metadataResolver,
-			ForkJoinPool forkJoinPool) {
+			ForkJoinPool forkJoinPool, MavenProperties mavenProperties) {
 		this.appRegistryService = appRegistryService;
 		this.metadataResolver = metadataResolver;
 		this.forkJoinPool = forkJoinPool;
+		this.mavenProperties = mavenProperties;
 	}
 
 	/**
@@ -193,9 +200,7 @@ public void register(@PathVariable("type") ApplicationType type, @PathVariable("
 	public void register(@PathVariable("type") ApplicationType type, @PathVariable("name") String name,
 			@RequestParam("uri") String uri, @RequestParam(name = "metadata-uri", required = false) String metadataUri,
 			@RequestParam(value = "force", defaultValue = "false") boolean force) {
-
-		Resource resource = this.appRegistryService.getResource(uri);
-		String version = ResourceUtils.getResourceVersion(resource);
+		String version = ResourceUtils.getResourceVersion(uri, this.mavenProperties);
 		this.register(type, name, version, uri, metadataUri, force);
 	}
 
@@ -263,7 +268,7 @@ public PagedResources<? extends AppRegistrationResource> registerAll(
 		List<AppRegistration> registrations = new ArrayList<>();
 
 		if (StringUtils.hasText(uri)) {
-			registrations.addAll(appRegistryService.importAll(force, this.appRegistryService.getResource(uri)));
+			registrations.addAll(appRegistryService.importAll(force, this.resourceLoader.getResource(uri)));
 		}
 		else if (!CollectionUtils.isEmpty(apps)) {
 			ByteArrayOutputStream baos = new ByteArrayOutputStream();