Set all strategies in CNM factory bean

ContentNegotiationManagerFactoryBean now provides an option to
explicitly set the strategies to use vs customizing a fixed
list of default strategies.

Issue: SPR-11114

spring-web/src/main/java/org/springframework/web/accept/ContentNegotiationManagerFactoryBean.java

@@ -36,9 +36,14 @@ import org.springframework.web.context.ServletContextAware;
 
 /**
  * Factory to create a {@code ContentNegotiationManager} and configure it with
- * one or more {@link ContentNegotiationStrategy} instances via simple setters.
- * The following table shows setters, resulting strategy instances, and if in
- * use by default:
+ * one or more {@link ContentNegotiationStrategy} instances.
+ *
+ * <p>As of 5.0 you can set the exact strategies to use via
+ * {@link #setStrategies(List)}.
+ *
+ * <p>As an alternative you can also rely on the set of defaults described below
+ * which can be turned on or off or customized through the methods of this
+ * builder:
  *
  * <table>
  * <tr>
@@ -73,17 +78,12 @@ import org.springframework.web.context.ServletContextAware;
  * </tr>
  * </table>
  *
- * <p>The order in which strategies are configured is fixed. Setters may only
- * turn individual strategies on or off. If you need a custom order for any
- * reason simply instantiate {@code ContentNegotiationManager} directly.
- *
- * <p>For the path extension and parameter strategies you may explicitly add
- * {@link #setMediaTypes MediaType mappings}. This will be used to resolve path
- * extensions or a parameter value such as "json" to a media type such as
- * "application/json".
- *
- * <p>The path extension strategy will also use {@link ServletContext#getMimeType}
- * and {@link MediaTypeFactory} to resolve a path extension to a MediaType.
+ * <strong>Note:</strong> if you must use URL-based content type resolution,
+ * the use of a query parameter is simpler and preferable to the use of a path
+ * extension since the latter can cause issues with URI variables, path
+ * parameters, and URI decoding. Consider setting {@link #setFavorPathExtension}
+ * to {@literal false} or otherwise set the strategies to use explicitly via
+ * {@link #setStrategies(List)}.
  *
  * @author Rossen Stoyanchev
  * @since 3.2
@@ -91,6 +91,10 @@ import org.springframework.web.context.ServletContextAware;
 public class ContentNegotiationManagerFactoryBean
 		implements FactoryBean<ContentNegotiationManager>, ServletContextAware, InitializingBean {
 
+	@Nullable
+	private List<ContentNegotiationStrategy> strategies;
+
+
 	private boolean favorPathExtension = true;
 
 	private boolean favorParameter = false;
@@ -116,6 +120,18 @@ public class ContentNegotiationManagerFactoryBean
 	private ServletContext servletContext;
 
 
+	/**
+	 * Set the exact list of strategies to use.
+	 * <p><strong>Note:</strong> use of this method is mutually exclusive with
+	 * use of all other setters in this class which customize a default, fixed
+	 * set of strategies. See class level doc for more details.
+	 * @param strategies the strategies to use
+	 * @since 5.0
+	 */
+	public void setStrategies(@Nullable List<ContentNegotiationStrategy> strategies) {
+		this.strategies = (strategies != null ? new ArrayList<>(strategies) : null);
+	}
+
 	/**
 	 * Whether the path extension in the URL path should be used to determine
 	 * the requested media type.
@@ -280,41 +296,46 @@ public class ContentNegotiationManagerFactoryBean
 	public ContentNegotiationManager build() {
 		List<ContentNegotiationStrategy> strategies = new ArrayList<>();
 
-		if (this.favorPathExtension) {
-			PathExtensionContentNegotiationStrategy strategy;
-			if (this.servletContext != null && !useRegisteredExtensionsOnly()) {
-				strategy = new ServletPathExtensionContentNegotiationStrategy(
-						this.servletContext, this.mediaTypes);
-			}
-			else {
-				strategy = new PathExtensionContentNegotiationStrategy(this.mediaTypes);
-			}
-			strategy.setIgnoreUnknownExtensions(this.ignoreUnknownPathExtensions);
-			if (this.useRegisteredExtensionsOnly != null) {
-				strategy.setUseRegisteredExtensionsOnly(this.useRegisteredExtensionsOnly);
-			}
-			strategies.add(strategy);
+		if (this.strategies != null) {
+			strategies.addAll(this.strategies);
 		}
-
-		if (this.favorParameter) {
-			ParameterContentNegotiationStrategy strategy =
-					new ParameterContentNegotiationStrategy(this.mediaTypes);
-			strategy.setParameterName(this.parameterName);
-			if (this.useRegisteredExtensionsOnly != null) {
-				strategy.setUseRegisteredExtensionsOnly(this.useRegisteredExtensionsOnly);
+		else {
+			if (this.favorPathExtension) {
+				PathExtensionContentNegotiationStrategy strategy;
+				if (this.servletContext != null && !useRegisteredExtensionsOnly()) {
+					strategy = new ServletPathExtensionContentNegotiationStrategy(
+							this.servletContext, this.mediaTypes);
+				}
+				else {
+					strategy = new PathExtensionContentNegotiationStrategy(this.mediaTypes);
+				}
+				strategy.setIgnoreUnknownExtensions(this.ignoreUnknownPathExtensions);
+				if (this.useRegisteredExtensionsOnly != null) {
+					strategy.setUseRegisteredExtensionsOnly(this.useRegisteredExtensionsOnly);
+				}
+				strategies.add(strategy);
 			}
-			else {
-				strategy.setUseRegisteredExtensionsOnly(true); // backwards compatibility
+
+			if (this.favorParameter) {
+				ParameterContentNegotiationStrategy strategy =
+						new ParameterContentNegotiationStrategy(this.mediaTypes);
+				strategy.setParameterName(this.parameterName);
+				if (this.useRegisteredExtensionsOnly != null) {
+					strategy.setUseRegisteredExtensionsOnly(this.useRegisteredExtensionsOnly);
+				}
+				else {
+					strategy.setUseRegisteredExtensionsOnly(true); // backwards compatibility
+				}
+				strategies.add(strategy);
 			}
-			strategies.add(strategy);
-		}
 
-		if (!this.ignoreAcceptHeader) {
-			strategies.add(new HeaderContentNegotiationStrategy());
-		}
+			if (!this.ignoreAcceptHeader) {
+				strategies.add(new HeaderContentNegotiationStrategy());
+			}
 
-		if (this.defaultNegotiationStrategy != null) {
-			strategies.add(this.defaultNegotiationStrategy);
+			if (this.defaultNegotiationStrategy != null) {
+				strategies.add(this.defaultNegotiationStrategy);
+			}
 		}
 
 		this.contentNegotiationManager = new ContentNegotiationManager(strategies);

spring-web/src/test/java/org/springframework/web/accept/ContentNegotiationManagerFactoryBeanTests.java

@@ -89,6 +89,25 @@ public class ContentNegotiationManagerFactoryBeanTests {
 				Collections.singletonList(MediaType.IMAGE_GIF), manager.resolveMediaTypes(this.webRequest));
 	}
 
+	@Test
+	public void explicitStrategies() throws Exception {
+		Map<String, MediaType> mediaTypes = Collections.singletonMap("bar", new MediaType("application", "bar"));
+		ParameterContentNegotiationStrategy strategy1 = new ParameterContentNegotiationStrategy(mediaTypes);
+		HeaderContentNegotiationStrategy strategy2 = new HeaderContentNegotiationStrategy();
+		List<ContentNegotiationStrategy> strategies = Arrays.asList(strategy1, strategy2);
+		this.factoryBean.setStrategies(strategies);
+		this.factoryBean.afterPropertiesSet();
+		ContentNegotiationManager manager = this.factoryBean.getObject();
+
+		assertEquals(strategies, manager.getStrategies());
+
+		this.servletRequest.setRequestURI("/flower");
+		this.servletRequest.addParameter("format", "bar");
+		assertEquals(Collections.singletonList(new MediaType("application", "bar")),
+				manager.resolveMediaTypes(this.webRequest));
+
+	}
+
 	@Test
 	public void favorPath() throws Exception {
 		this.factoryBean.setFavorPathExtension(true);

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/ContentNegotiationConfigurer.java

@@ -18,6 +18,7 @@ package org.springframework.web.servlet.config.annotation;
 
 import java.util.Arrays;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import javax.servlet.ServletContext;
 
@@ -34,9 +35,14 @@ import org.springframework.web.accept.PathExtensionContentNegotiationStrategy;
 
 /**
  * Creates a {@code ContentNegotiationManager} and configures it with
- * one or more {@link ContentNegotiationStrategy} instances. The following shows
- * the resulting strategy instances, the methods used to configured them, and
- * whether enabled by default:
+ * one or more {@link ContentNegotiationStrategy} instances.
+ *
+ * <p>As of 5.0 you can set the exact strategies to use via
+ * {@link #strategies(List)}.
+ *
+ * <p>As an alternative you can also rely on the set of defaults described below
+ * which can be turned on or off or customized through the methods of this
+ * builder:
  *
  * <table>
  * <tr>
@@ -74,14 +80,12 @@ import org.springframework.web.accept.PathExtensionContentNegotiationStrategy;
  * <p>The order in which strategies are configured is fixed. You can only turn
  * them on or off.
  *
- * <p>For the path extension and parameter strategies you may explicitly add
- * {@link #mediaType MediaType mappings}. Those will be used to resolve path
- * extensions and/or a query parameter value such as "json" to a concrete media
- * type such as "application/json".
- *
- * <p>The path extension strategy will also use {@link ServletContext#getMimeType}
- * and the {@link MediaTypeFactory} to resolve a path
- * extension to a MediaType.
+ * <strong>Note:</strong> if you must use URL-based content type resolution,
+ * the use of a query parameter is simpler and preferable to the use of a path
+ * extension since the latter can cause issues with URI variables, path
+ * parameters, and URI decoding. Consider setting {@link #favorPathExtension}
+ * to {@literal false} or otherwise set the strategies to use explicitly via
+ * {@link #strategies(List)}.
  *
  * @author Rossen Stoyanchev
  * @since 3.2
@@ -103,6 +107,18 @@ public class ContentNegotiationConfigurer {
 	}
 
 
+	/**
+	 * Set the exact list of strategies to use.
+	 * <p><strong>Note:</strong> use of this method is mutually exclusive with
+	 * use of all other setters in this class which customize a default, fixed
+	 * set of strategies. See class level doc for more details.
+	 * @param strategies the strategies to use
+	 * @since 5.0
+	 */
+	public void strategies(@Nullable List<ContentNegotiationStrategy> strategies) {
+		this.factory.setStrategies(strategies);
+	}
+
 	/**
 	 * Whether the path extension in the URL path should be used to determine
 	 * the requested media type.

src/docs/asciidoc/web/web-mvc.adoc

@@ -5198,10 +5198,14 @@ And in XML use the `<mvc:interceptors>` element:
 [[mvc-config-content-negotiation]]
 === Content Negotiation
 You can configure how Spring MVC determines the requested media types from the request.
-The available options are to check the URL path for a file extension, check the
-"Accept" header, a specific query parameter, or to fall back on a default content
-type when nothing is requested. By default the path extension in the request URI
-is checked first and the "Accept" header is checked second.
+The available options are to check a query parameter, the URL path for a file extension,
+the "Accept" header, use a fixed list, or a custom strategy.
+
+By default for backwards compatibility the path extension in the request URI is checked
+first and the "Accept" header is checked second. However if you must use URL-based content
+type resolution, we highly recommend using the query parameter strategy over the path
+extension since the latter can cause issues with URI variables, path parameters, and also
+in combination with URI decoding.
 
 The MVC Java config and the MVC namespace register `json`, `xml`, `rss`, `atom` by
 default if corresponding dependencies are on the classpath. Additional