Avoid expensive isReadable() check during classpath scan

Closes gh-27541
See gh-21372

Author: jhoeller

spring-context/src/main/java/org/springframework/context/annotation/ClassPathScanningCandidateComponentProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,11 +16,12 @@
 
 package org.springframework.context.annotation;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.lang.annotation.Annotation;
+import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.LinkedHashSet;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Set;
 
@@ -93,9 +94,9 @@ public class ClassPathScanningCandidateComponentProvider implements EnvironmentC
 
 	private String resourcePattern = DEFAULT_RESOURCE_PATTERN;
 
-	private final List<TypeFilter> includeFilters = new LinkedList<>();
+	private final List<TypeFilter> includeFilters = new ArrayList<>();
 
-	private final List<TypeFilter> excludeFilters = new LinkedList<>();
+	private final List<TypeFilter> excludeFilters = new ArrayList<>();
 
 	@Nullable
 	private Environment environment;
@@ -424,40 +425,38 @@ private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
 				if (traceEnabled) {
 					logger.trace("Scanning " + resource);
 				}
-				if (resource.isReadable()) {
-					try {
-						MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
-						if (isCandidateComponent(metadataReader)) {
-							ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
-							sbd.setSource(resource);
-							if (isCandidateComponent(sbd)) {
-								if (debugEnabled) {
-									logger.debug("Identified candidate component class: " + resource);
-								}
-								candidates.add(sbd);
-							}
-							else {
-								if (debugEnabled) {
-									logger.debug("Ignored because not a concrete top-level class: " + resource);
-								}
+				try {
+					MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
+					if (isCandidateComponent(metadataReader)) {
+						ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
+						sbd.setSource(resource);
+						if (isCandidateComponent(sbd)) {
+							if (debugEnabled) {
+								logger.debug("Identified candidate component class: " + resource);
 							}
+							candidates.add(sbd);
 						}
 						else {
-							if (traceEnabled) {
-								logger.trace("Ignored because not matching any filter: " + resource);
+							if (debugEnabled) {
+								logger.debug("Ignored because not a concrete top-level class: " + resource);
 							}
 						}
 					}
-					catch (Throwable ex) {
-						throw new BeanDefinitionStoreException(
-								"Failed to read candidate component class: " + resource, ex);
+					else {
+						if (traceEnabled) {
+							logger.trace("Ignored because not matching any filter: " + resource);
+						}
 					}
 				}
-				else {
+				catch (FileNotFoundException ex) {
 					if (traceEnabled) {
-						logger.trace("Ignored because not readable: " + resource);
+						logger.trace("Ignored non-readable " + resource + ": " + ex.getMessage());
 					}
 				}
+				catch (Throwable ex) {
+					throw new BeanDefinitionStoreException(
+							"Failed to read candidate component class: " + resource, ex);
+				}
 			}
 		}
 		catch (IOException ex) {

spring-core/src/main/java/org/springframework/core/io/InputStreamSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -48,8 +48,9 @@ public interface InputStreamSource {
 	 * creating mail attachments. For such a use case, it is <i>required</i>
 	 * that each {@code getInputStream()} call returns a fresh stream.
 	 * @return the input stream for the underlying resource (must not be {@code null})
-	 * @throws java.io.FileNotFoundException if the underlying resource doesn't exist
+	 * @throws java.io.FileNotFoundException if the underlying resource does not exist
 	 * @throws IOException if the content stream could not be opened
+	 * @see Resource#isReadable()
 	 */
 	InputStream getInputStream() throws IOException;
 

spring-orm/src/main/java/org/springframework/orm/hibernate5/LocalSessionFactoryBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.orm.hibernate5;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.InvocationTargetException;
@@ -349,7 +350,7 @@ public LocalSessionFactoryBuilder scanPackages(String... packagesToScan) throws
 				Resource[] resources = this.resourcePatternResolver.getResources(pattern);
 				MetadataReaderFactory readerFactory = new CachingMetadataReaderFactory(this.resourcePatternResolver);
 				for (Resource resource : resources) {
-					if (resource.isReadable()) {
+					try {
 						MetadataReader reader = readerFactory.getMetadataReader(resource);
 						String className = reader.getClassMetadata().getClassName();
 						if (matchesEntityTypeFilter(reader, readerFactory)) {
@@ -362,6 +363,9 @@ else if (className.endsWith(PACKAGE_INFO_SUFFIX)) {
 							packageNames.add(className.substring(0, className.length() - PACKAGE_INFO_SUFFIX.length()));
 						}
 					}
+					catch (FileNotFoundException ex) {
+						// Ignore non-readable resource
+					}
 				}
 			}
 		}

spring-orm/src/main/java/org/springframework/orm/jpa/persistenceunit/DefaultPersistenceUnitManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,12 +16,13 @@
 
 package org.springframework.orm.jpa.persistenceunit;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.URL;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashSet;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -498,7 +499,7 @@ public void preparePersistenceUnitInfos() {
 	 * as defined in the JPA specification.
 	 */
 	private List<SpringPersistenceUnitInfo> readPersistenceUnitInfos() {
-		List<SpringPersistenceUnitInfo> infos = new LinkedList<>();
+		List<SpringPersistenceUnitInfo> infos = new ArrayList<>(1);
 		String defaultName = this.defaultPersistenceUnitName;
 		boolean buildDefaultUnit = (this.packagesToScan != null || this.mappingResources != null);
 		boolean foundDefaultUnit = false;
@@ -585,7 +586,7 @@ private void scanPackage(SpringPersistenceUnitInfo scannedUnit, String pkg) {
 			Resource[] resources = this.resourcePatternResolver.getResources(pattern);
 			MetadataReaderFactory readerFactory = new CachingMetadataReaderFactory(this.resourcePatternResolver);
 			for (Resource resource : resources) {
-				if (resource.isReadable()) {
+				try {
 					MetadataReader reader = readerFactory.getMetadataReader(resource);
 					String className = reader.getClassMetadata().getClassName();
 					if (matchesFilter(reader, readerFactory)) {
@@ -602,6 +603,9 @@ else if (className.endsWith(PACKAGE_INFO_SUFFIX)) {
 								className.substring(0, className.length() - PACKAGE_INFO_SUFFIX.length()));
 					}
 				}
+				catch (FileNotFoundException ex) {
+					// Ignore non-readable resource
+				}
 			}
 		}
 		catch (IOException ex) {