ResourceHandlerRegistration exposes List<Resource> locations

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/ResourceHandlerRegistration.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.
@@ -42,6 +42,8 @@ public class ResourceHandlerRegistration {
 
 	private final List<String> locationValues = new ArrayList<>();
 
+	private final List<Resource> locationsResources = new ArrayList<>();
+
 	@Nullable
 	private Integer cachePeriod;
 
@@ -82,8 +84,21 @@ public ResourceHandlerRegistration(String... pathPatterns) {
 	 * @return the same {@link ResourceHandlerRegistration} instance, for
 	 * chained method invocation
 	 */
-	public ResourceHandlerRegistration addResourceLocations(String... resourceLocations) {
-		this.locationValues.addAll(Arrays.asList(resourceLocations));
+	public ResourceHandlerRegistration addResourceLocations(String... locations) {
+		this.locationValues.addAll(Arrays.asList(locations));
+		return this;
+	}
+
+	/**
+	 * Configure locations to serve static resources from based on pre-resolved
+	 * {@code Resource} references.
+	 * @param locations the resource locations to use
+	 * @return the same {@link ResourceHandlerRegistration} instance, for
+	 * chained method invocation
+	 * @since 5.3.3
+	 */
+	public ResourceHandlerRegistration addResourceLocations(Resource... locations) {
+		this.locationsResources.addAll(Arrays.asList(locations));
 		return this;
 	}
 
@@ -181,6 +196,7 @@ protected ResourceHttpRequestHandler getRequestHandler() {
 			handler.setResourceTransformers(this.resourceChainRegistration.getResourceTransformers());
 		}
 		handler.setLocationValues(this.locationValues);
+		handler.setLocations(this.locationsResources);
 		if (this.cacheControl != null) {
 			handler.setCacheControl(this.cacheControl);
 		}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.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.
@@ -21,12 +21,10 @@
 import java.net.URLDecoder;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.stream.Collectors;
 
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
@@ -69,9 +67,10 @@
  * {@code HttpRequestHandler} that serves static resources in an optimized way
  * according to the guidelines of Page Speed, YSlow, etc.
  *
- * <p>The {@linkplain #setLocations "locations"} property takes a list of Spring
- * {@link Resource} locations from which static resources are allowed to be served
- * by this handler. Resources could be served from a classpath location, e.g.
+ * <p>The properties {@linkplain #setLocations "locations"} and
+ * {@linkplain #setLocationValues "locationValues"} accept locations from which
+ * static resources can be served by this handler. This can be relative to the
+ * root of the web application, or from the classpath, e.g.
  * "classpath:/META-INF/public-web-resources/", allowing convenient packaging
  * and serving of resources such as .js, .css, and others in jar files.
  *
@@ -106,7 +105,9 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 
 	private final List<String> locationValues = new ArrayList<>(4);
 
-	private final List<Resource> locations = new ArrayList<>(4);
+	private final List<Resource> locationResources = new ArrayList<>(4);
+
+	private final List<Resource> locationsToUse = new ArrayList<>(4);
 
 	private final Map<Resource, Charset> locationCharsets = new HashMap<>(4);
 
@@ -149,40 +150,52 @@ public ResourceHttpRequestHandler() {
 
 
 	/**
-	 * An alternative to {@link #setLocations(List)} that accepts a list of
-	 * String-based location values, with support for {@link UrlResource}'s
-	 * (e.g. files or HTTP URLs) with a special prefix to indicate the charset
-	 * to use when appending relative paths. For example
+	 * Configure String-based locations to serve resources from.
+	 * <p>For example, {{@code "/"}, {@code "classpath:/META-INF/public-web-resources/"}}
+	 * allows resources to be served both from the web application root and
+	 * from any JAR on the classpath that contains a
+	 * {@code /META-INF/public-web-resources/} directory, with resources in the
+	 * web application root taking precedence.
+	 * <p>For {@link org.springframework.core.io.UrlResource URL-based resources}
+	 * (e.g. files, HTTP URLs, etc) this method supports a special prefix to
+	 * indicate the charset associated with the URL so that relative paths
+	 * appended to it can be encoded correctly, for example
 	 * {@code "[charset=Windows-31J]https://example.org/path"}.
 	 * @since 4.3.13
+	 * @see #setLocations(List)
 	 */
-	public void setLocationValues(List<String> locationValues) {
-		Assert.notNull(locationValues, "Location values list must not be null");
+	public void setLocationValues(List<String> locations) {
+		Assert.notNull(locations, "Locations list must not be null");
 		this.locationValues.clear();
-		this.locationValues.addAll(locationValues);
+		this.locationValues.addAll(locations);
 	}
 
 	/**
-	 * Set the {@code List} of {@code Resource} locations to use as sources
-	 * for serving static resources.
+	 * Configure locations to serve resources from as pre-resourced Resource's.
 	 * @see #setLocationValues(List)
 	 */
 	public void setLocations(List<Resource> locations) {
 		Assert.notNull(locations, "Locations list must not be null");
-		this.locations.clear();
-		this.locations.addAll(locations);
+		this.locationResources.clear();
+		this.locationResources.addAll(locations);
 	}
 
 	/**
-	 * Return the configured {@code List} of {@code Resource} locations.
-	 * <p>Note that if {@link #setLocationValues(List) locationValues} are provided,
-	 * instead of loaded Resource-based locations, this method will return
-	 * empty until after initialization via {@link #afterPropertiesSet()}.
+	 * Return the configured {@code List} of {@code Resource} locations including
+	 * both String-based locations provided via
+	 * {@link #setLocationValues(List) setLocationValues} and pre-resolved {@code Resource}
+	 * locations provided via {@link #setLocations(List) setLocations}.
+	 * <p>Note that the returned list is fully initialized only after
+	 * initialization via {@link #afterPropertiesSet()}.
 	 * @see #setLocationValues
 	 * @see #setLocations
 	 */
 	public List<Resource> getLocations() {
-		return this.locations;
+		if (this.locationsToUse.isEmpty()) {
+			// Possibly not yet initialized, return only what we have so far
+			return this.locationResources;
+		}
+		return this.locationsToUse;
 	}
 
 	/**
@@ -374,7 +387,7 @@ public void setUseLastModified(boolean useLastModified) {
 	public void afterPropertiesSet() throws Exception {
 		resolveResourceLocations();
 
-		if (logger.isWarnEnabled() && CollectionUtils.isEmpty(this.locations)) {
+		if (logger.isWarnEnabled() && CollectionUtils.isEmpty(getLocations())) {
 			logger.warn("Locations list is empty. No resources will be served unless a " +
 					"custom ResourceResolver is configured as an alternative to PathResourceResolver.");
 		}
@@ -410,43 +423,38 @@ public void afterPropertiesSet() throws Exception {
 	}
 
 	private void resolveResourceLocations() {
-		if (CollectionUtils.isEmpty(this.locationValues)) {
-			return;
-		}
-		else if (!CollectionUtils.isEmpty(this.locations)) {
-			throw new IllegalArgumentException("Please set either Resource-based \"locations\" or " +
-					"String-based \"locationValues\", but not both.");
-		}
-
-		ApplicationContext applicationContext = obtainApplicationContext();
-		for (String location : this.locationValues) {
-			if (this.embeddedValueResolver != null) {
-				String resolvedLocation = this.embeddedValueResolver.resolveStringValue(location);
-				if (resolvedLocation == null) {
-					throw new IllegalArgumentException("Location resolved to null: " + location);
+		if (!this.locationValues.isEmpty()) {
+			ApplicationContext applicationContext = obtainApplicationContext();
+			for (String location : this.locationValues) {
+				if (this.embeddedValueResolver != null) {
+					String resolvedLocation = this.embeddedValueResolver.resolveStringValue(location);
+					if (resolvedLocation == null) {
+						throw new IllegalArgumentException("Location resolved to null: " + location);
+					}
+					location = resolvedLocation;
 				}
-				location = resolvedLocation;
-			}
-			Charset charset = null;
-			location = location.trim();
-			if (location.startsWith(URL_RESOURCE_CHARSET_PREFIX)) {
-				int endIndex = location.indexOf(']', URL_RESOURCE_CHARSET_PREFIX.length());
-				if (endIndex == -1) {
-					throw new IllegalArgumentException("Invalid charset syntax in location: " + location);
+				Charset charset = null;
+				location = location.trim();
+				if (location.startsWith(URL_RESOURCE_CHARSET_PREFIX)) {
+					int endIndex = location.indexOf(']', URL_RESOURCE_CHARSET_PREFIX.length());
+					if (endIndex == -1) {
+						throw new IllegalArgumentException("Invalid charset syntax in location: " + location);
+					}
+					String value = location.substring(URL_RESOURCE_CHARSET_PREFIX.length(), endIndex);
+					charset = Charset.forName(value);
+					location = location.substring(endIndex + 1);
 				}
-				String value = location.substring(URL_RESOURCE_CHARSET_PREFIX.length(), endIndex);
-				charset = Charset.forName(value);
-				location = location.substring(endIndex + 1);
-			}
-			Resource resource = applicationContext.getResource(location);
-			this.locations.add(resource);
-			if (charset != null) {
-				if (!(resource instanceof UrlResource)) {
-					throw new IllegalArgumentException("Unexpected charset for non-UrlResource: " + resource);
+				Resource resource = applicationContext.getResource(location);
+				this.locationsToUse.add(resource);
+				if (charset != null) {
+					if (!(resource instanceof UrlResource)) {
+						throw new IllegalArgumentException("Unexpected charset for non-UrlResource: " + resource);
+					}
+					this.locationCharsets.put(resource, charset);
 				}
-				this.locationCharsets.put(resource, charset);
 			}
 		}
+		this.locationsToUse.addAll(this.locationResources);
 	}
 
 	/**
@@ -455,7 +463,7 @@ else if (!CollectionUtils.isEmpty(this.locations)) {
 	 * match the {@link #setLocations locations} configured on this class.
 	 */
 	protected void initAllowedLocations() {
-		if (CollectionUtils.isEmpty(this.locations)) {
+		if (CollectionUtils.isEmpty(getLocations())) {
 			return;
 		}
 		for (int i = getResourceResolvers().size() - 1; i >= 0; i--) {
@@ -785,17 +793,6 @@ protected void setHeaders(HttpServletResponse response, Resource resource, @Null
 
 	@Override
 	public String toString() {
-		return "ResourceHttpRequestHandler " + formatLocations();
+		return "ResourceHttpRequestHandler " + getLocations();
 	}
-
-	private Object formatLocations() {
-		if (!this.locationValues.isEmpty()) {
-			return this.locationValues.stream().collect(Collectors.joining("\", \"", "[\"", "\"]"));
-		}
-		else if (!this.locations.isEmpty()) {
-			return this.locations;
-		}
-		return Collections.emptyList();
-	}
-
 }