Polish 'Align MimeMappings with Tomcat's defaults'

Refine `MimeMappings` so that common default mappings are included
by default and the complete set is only loaded when needed.

The `TomcatServletWebServerFactory` has been updated so that if
`TomcatEmbeddedContext` is in use the mime mapping are used
directly rather than being copied to another Map.

The `AbstractServletWebServerFactory` class has also been changed
to use a lazy copy of the mappings. This should mean that the
complete set of properties is only loaded if the user mutates
the mappings.

See gh-32101

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatEmbeddedContext.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.web.embedded.tomcat;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
@@ -30,6 +31,7 @@ import org.apache.catalina.core.StandardContext;
 import org.apache.catalina.core.StandardWrapper;
 import org.apache.catalina.session.ManagerBase;
 
+import org.springframework.boot.web.server.MimeMappings;
 import org.springframework.boot.web.server.WebServerException;
 import org.springframework.util.ClassUtils;
 
@@ -44,6 +46,8 @@ class TomcatEmbeddedContext extends StandardContext {
 
 	private TomcatStarter starter;
 
+	private MimeMappings mimeMappings;
+
 	@Override
 	public boolean loadOnStartup(Container[] children) {
 		// deferred until later (see deferredLoadOnStartup)
@@ -118,4 +122,27 @@ class TomcatEmbeddedContext extends StandardContext {
 		return this.starter;
 	}
 
+	void setMimeMappings(MimeMappings mimeMappings) {
+		this.mimeMappings = mimeMappings;
+	}
+
+	@Override
+	public String[] findMimeMappings() {
+		List<String> mappings = new ArrayList<>();
+		mappings.addAll(Arrays.asList(super.findMimeMappings()));
+		if (this.mimeMappings != null) {
+			this.mimeMappings.forEach((mapping) -> mappings.add(mapping.getExtension()));
+		}
+		return mappings.toArray(String[]::new);
+	}
+
+	@Override
+	public String findMimeMapping(String extension) {
+		String mimeMapping = super.findMimeMapping(extension);
+		if (mimeMapping != null) {
+			return mimeMapping;
+		}
+		return (this.mimeMappings != null) ? this.mimeMappings.get(extension) : null;
+	}
+
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java

@@ -389,9 +389,7 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 			tomcatErrorPage.setExceptionType(errorPage.getExceptionName());
 			context.addErrorPage(tomcatErrorPage);
 		}
-		for (MimeMappings.Mapping mapping : getMimeMappings()) {
-			context.addMimeMapping(mapping.getExtension(), mapping.getMimeType());
-		}
+		setMimeMappings(context);
 		configureSession(context);
 		configureCookieProcessor(context);
 		new DisableReferenceClearingContextCustomizer().customize(context);
@@ -423,6 +421,16 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 		}
 	}
 
+	private void setMimeMappings(Context context) {
+		if (context instanceof TomcatEmbeddedContext embeddedContext) {
+			embeddedContext.setMimeMappings(getMimeMappings());
+			return;
+		}
+		for (MimeMappings.Mapping mapping : getMimeMappings()) {
+			context.addMimeMapping(mapping.getExtension(), mapping.getMimeType());
+		}
+	}
+
 	private void configureCookieProcessor(Context context) {
 		SameSite sessionSameSite = getSession().getCookie().getSameSite();
 		List<CookieSameSiteSupplier> suppliers = new ArrayList<>();

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/MimeMappings.java

@@ -21,9 +21,13 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
+import java.util.Locale;
 import java.util.Map;
-import java.util.Properties;
+import java.util.Map.Entry;
+import java.util.concurrent.atomic.AtomicBoolean;
 
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.support.PropertiesLoaderUtils;
 import org.springframework.util.Assert;
@@ -33,29 +37,15 @@ import org.springframework.util.Assert;
  * {@literal <mime-mapping>} element traditionally found in web.xml.
  *
  * @author Phillip Webb
+ * @author Guirong Hu
  * @since 2.0.0
  */
-public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
+public sealed class MimeMappings implements Iterable<MimeMappings.Mapping> {
 
 	/**
 	 * Default mime mapping commonly used.
 	 */
-	public static final MimeMappings DEFAULT;
-
-	static {
-		MimeMappings mappings = new MimeMappings();
-		try {
-			Properties defaultMimeMappings = PropertiesLoaderUtils
-					.loadProperties(new ClassPathResource("mime-mappings.properties", MimeMappings.class));
-			for (String extension : defaultMimeMappings.stringPropertyNames()) {
-				mappings.add(extension, defaultMimeMappings.getProperty(extension));
-			}
-		}
-		catch (IOException ex) {
-			throw new IllegalArgumentException("Unable to load the default MIME types", ex);
-		}
-		DEFAULT = unmodifiableMappings(mappings);
-	}
+	public static final MimeMappings DEFAULT = new DefaultMimeMappings();
 
 	private final Map<String, Mapping> map;
 
@@ -90,24 +80,11 @@ public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
 	 * @param mappings source mappings
 	 * @param mutable if the new object should be mutable.
 	 */
-	private MimeMappings(MimeMappings mappings, boolean mutable) {
+	MimeMappings(MimeMappings mappings, boolean mutable) {
 		Assert.notNull(mappings, "Mappings must not be null");
 		this.map = (mutable ? new LinkedHashMap<>(mappings.map) : Collections.unmodifiableMap(mappings.map));
 	}
 
-	@Override
-	public Iterator<Mapping> iterator() {
-		return getAll().iterator();
-	}
-
-	/**
-	 * Returns all defined mappings.
-	 * @return the mappings.
-	 */
-	public Collection<Mapping> getAll() {
-		return this.map.values();
-	}
-
 	/**
 	 * Add a new mime mapping.
 	 * @param extension the file extension (excluding '.')
@@ -115,7 +92,20 @@ public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
 	 * @return any previous mapping or {@code null}
 	 */
 	public String add(String extension, String mimeType) {
-		Mapping previous = this.map.put(extension, new Mapping(extension, mimeType));
+		Assert.notNull(extension, "Extension must not be null");
+		Assert.notNull(mimeType, "MimeType must not be null");
+		Mapping previous = this.map.put(extension.toLowerCase(Locale.ENGLISH), new Mapping(extension, mimeType));
+		return (previous != null) ? previous.getMimeType() : null;
+	}
+
+	/**
+	 * Remove an existing mapping.
+	 * @param extension the file extension (excluding '.')
+	 * @return the removed mime mapping or {@code null} if no item was removed
+	 */
+	public String remove(String extension) {
+		Assert.notNull(extension, "Extension must not be null");
+		Mapping previous = this.map.remove(extension.toLowerCase(Locale.ENGLISH));
 		return (previous != null) ? previous.getMimeType() : null;
 	}
 
@@ -125,18 +115,22 @@ public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
 	 * @return a mime mapping or {@code null}
 	 */
 	public String get(String extension) {
-		Mapping mapping = this.map.get(extension);
+		Assert.notNull(extension, "Extension must not be null");
+		Mapping mapping = this.map.get(extension.toLowerCase(Locale.ENGLISH));
 		return (mapping != null) ? mapping.getMimeType() : null;
 	}
 
 	/**
-	 * Remove an existing mapping.
-	 * @param extension the file extension (excluding '.')
-	 * @return the removed mime mapping or {@code null} if no item was removed
+	 * Returns all defined mappings.
+	 * @return the mappings.
 	 */
-	public String remove(String extension) {
-		Mapping previous = this.map.remove(extension);
-		return (previous != null) ? previous.getMimeType() : null;
+	public Collection<Mapping> getAll() {
+		return this.map.values();
+	}
+
+	@Override
+	public final Iterator<Mapping> iterator() {
+		return getAll().iterator();
 	}
 
 	@Override
@@ -148,14 +142,18 @@ public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
 			return true;
 		}
 		if (obj instanceof MimeMappings other) {
-			return this.map.equals(other.map);
+			return getMap().equals(other.map);
 		}
 		return false;
 	}
 
 	@Override
 	public int hashCode() {
-		return this.map.hashCode();
+		return getMap().hashCode();
+	}
+
+	Map<String, Mapping> getMap() {
+		return this.map;
 	}
 
 	/**
@@ -165,9 +163,22 @@ public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
 	 * @return an unmodifiable view of the specified mappings.
 	 */
 	public static MimeMappings unmodifiableMappings(MimeMappings mappings) {
+		Assert.notNull(mappings, "Mappings must not be null");
 		return new MimeMappings(mappings, false);
 	}
 
+	/**
+	 * Crate a new lazy copy of the given mappings will only copy entries if the mappings
+	 * are mutated.
+	 * @param mappings the source mappings
+	 * @return a new mappings instance
+	 * @since 3.0.0
+	 */
+	public static MimeMappings lazyCopy(MimeMappings mappings) {
+		Assert.notNull(mappings, "Mappings must not be null");
+		return new LazyMimeMappingsCopy(mappings);
+	}
+
 	/**
 	 * A single mime mapping.
 	 */
@@ -218,4 +229,175 @@ public final class MimeMappings implements Iterable<MimeMappings.Mapping> {
 
 	}
 
+	/**
+	 * {@link MimeMappings} implementation used for {@link MimeMappings#DEFAULT}. Provides
+	 * in-memory access for common mappings and lazily loads the complete set when
+	 * necessary.
+	 */
+	static final class DefaultMimeMappings extends MimeMappings {
+
+		static final String MIME_MAPPINGS_PROPERTIES = "mime-mappings.properties";
+
+		private static final MimeMappings COMMON;
+
+		static {
+			MimeMappings mappings = new MimeMappings();
+			mappings.add("avi", "video/x-msvideo");
+			mappings.add("bin", "application/octet-stream");
+			mappings.add("body", "text/html");
+			mappings.add("class", "application/java");
+			mappings.add("css", "text/css");
+			mappings.add("dtd", "application/xml-dtd");
+			mappings.add("gif", "image/gif");
+			mappings.add("gtar", "application/x-gtar");
+			mappings.add("gz", "application/x-gzip");
+			mappings.add("htm", "text/html");
+			mappings.add("html", "text/html");
+			mappings.add("jar", "application/java-archive");
+			mappings.add("java", "text/x-java-source");
+			mappings.add("jnlp", "application/x-java-jnlp-file");
+			mappings.add("jpe", "image/jpeg");
+			mappings.add("jpeg", "image/jpeg");
+			mappings.add("jpg", "image/jpeg");
+			mappings.add("js", "application/javascript");
+			mappings.add("json", "application/json");
+			mappings.add("otf", "application/x-font-opentype");
+			mappings.add("pdf", "application/pdf");
+			mappings.add("png", "image/png");
+			mappings.add("ps", "application/postscript");
+			mappings.add("tar", "application/x-tar");
+			mappings.add("tif", "image/tiff");
+			mappings.add("tiff", "image/tiff");
+			mappings.add("ttf", "application/x-font-ttf");
+			mappings.add("txt", "text/plain");
+			mappings.add("xht", "application/xhtml+xml");
+			mappings.add("xhtml", "application/xhtml+xml");
+			mappings.add("xls", "application/vnd.ms-excel");
+			mappings.add("xml", "application/xml");
+			mappings.add("xsl", "application/xml");
+			mappings.add("xslt", "application/xslt+xml");
+			mappings.add("wasm", "application/wasm");
+			mappings.add("zip", "application/zip");
+			COMMON = unmodifiableMappings(mappings);
+		}
+
+		private volatile Map<String, Mapping> loaded;
+
+		DefaultMimeMappings() {
+			super(new MimeMappings(), false);
+		}
+
+		@Override
+		public Collection<Mapping> getAll() {
+			return load().values();
+		}
+
+		@Override
+		public String get(String extension) {
+			Assert.notNull(extension, "Extension must not be null");
+			extension = extension.toLowerCase(Locale.ENGLISH);
+			Map<String, Mapping> loaded = this.loaded;
+			if (loaded != null) {
+				return get(loaded, extension);
+			}
+			String commonMimeType = COMMON.get(extension);
+			if (commonMimeType != null) {
+				return commonMimeType;
+			}
+			loaded = load();
+			return get(loaded, extension);
+		}
+
+		private String get(Map<String, Mapping> mappings, String extension) {
+			Mapping mapping = mappings.get(extension);
+			return (mapping != null) ? mapping.getMimeType() : null;
+		}
+
+		@Override
+		Map<String, Mapping> getMap() {
+			return load();
+		}
+
+		private Map<String, Mapping> load() {
+			Map<String, Mapping> loaded = this.loaded;
+			if (loaded != null) {
+				return loaded;
+			}
+			try {
+				loaded = new LinkedHashMap<>();
+				for (Entry<?, ?> entry : PropertiesLoaderUtils
+						.loadProperties(new ClassPathResource(MIME_MAPPINGS_PROPERTIES, getClass())).entrySet()) {
+					loaded.put((String) entry.getKey(),
+							new Mapping((String) entry.getKey(), (String) entry.getValue()));
+				}
+				loaded = Collections.unmodifiableMap(loaded);
+				this.loaded = loaded;
+				return loaded;
+			}
+			catch (IOException ex) {
+				throw new IllegalArgumentException("Unable to load the default MIME types", ex);
+			}
+		}
+
+	}
+
+	/**
+	 * {@link MimeMappings} implementation used to create a lazy copy only when the
+	 * mappings are mutated.
+	 */
+	static final class LazyMimeMappingsCopy extends MimeMappings {
+
+		private final MimeMappings source;
+
+		private AtomicBoolean copied = new AtomicBoolean();
+
+		LazyMimeMappingsCopy(MimeMappings source) {
+			this.source = source;
+		}
+
+		@Override
+		public String add(String extension, String mimeType) {
+			copyIfNecessary();
+			return super.add(extension, mimeType);
+		}
+
+		@Override
+		public String remove(String extension) {
+			copyIfNecessary();
+			return super.remove(extension);
+		}
+
+		private void copyIfNecessary() {
+			if (this.copied.compareAndSet(false, true)) {
+				this.source.forEach((mapping) -> add(mapping.getExtension(), mapping.getMimeType()));
+			}
+		}
+
+		@Override
+		public String get(String extension) {
+			return !this.copied.get() ? this.source.get(extension) : super.get(extension);
+		}
+
+		@Override
+		public Collection<Mapping> getAll() {
+			return !this.copied.get() ? this.source.getAll() : super.getAll();
+		}
+
+		@Override
+		Map<String, Mapping> getMap() {
+			return !this.copied.get() ? this.source.getMap() : super.getMap();
+		}
+
+	}
+
+	static class MimeMappingsRuntimeHints implements RuntimeHintsRegistrar {
+
+		@Override
+		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+			hints.resources().registerPattern(
+					"org/springframework/boot/web/server/" + DefaultMimeMappings.MIME_MAPPINGS_PROPERTIES);
+		}
+
+	}
+
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactory.java

@@ -69,7 +69,7 @@ public abstract class AbstractServletWebServerFactory extends AbstractConfigurab
 
 	private boolean registerDefaultServlet = false;
 
-	private MimeMappings mimeMappings = new MimeMappings(MimeMappings.DEFAULT);
+	private MimeMappings mimeMappings = MimeMappings.lazyCopy(MimeMappings.DEFAULT);
 
 	private List<ServletContextInitializer> initializers = new ArrayList<>();
 
@@ -173,6 +173,7 @@ public abstract class AbstractServletWebServerFactory extends AbstractConfigurab
 
 	@Override
 	public void setMimeMappings(MimeMappings mimeMappings) {
+		Assert.notNull(mimeMappings, "MimeMappings must not be null");
 		this.mimeMappings = new MimeMappings(mimeMappings);
 	}
 

spring-boot-project/spring-boot/src/main/resources/META-INF/spring/aot.factories

@@ -1,11 +1,12 @@
 org.springframework.aot.hint.RuntimeHintsRegistrar=\
+org.springframework.boot.SpringApplication.SpringApplicationRuntimeHints,\
+org.springframework.boot.WebApplicationType.WebApplicationTypeRuntimeHints,\
 org.springframework.boot.context.config.ConfigDataLocationRuntimeHints,\
 org.springframework.boot.env.PropertySourceRuntimeHints,\
 org.springframework.boot.json.JacksonRuntimeHints,\
 org.springframework.boot.logging.java.JavaLoggingSystemRuntimeHints,\
 org.springframework.boot.logging.logback.LogbackRuntimeHints,\
-org.springframework.boot.SpringApplication.SpringApplicationRuntimeHints,\
-org.springframework.boot.WebApplicationType.WebApplicationTypeRuntimeHints
+org.springframework.boot.web.server.MimeMappings.MimeMappingsRuntimeHints
 
 org.springframework.beans.factory.aot.BeanFactoryInitializationAotProcessor=\
 org.springframework.boot.context.properties.ConfigurationPropertiesBeanFactoryInitializationAotProcessor

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/server/MimeMappingsTests.java

@@ -24,6 +24,13 @@ import java.util.regex.Pattern;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.predicate.RuntimeHintsPredicates;
+import org.springframework.boot.web.server.MimeMappings.DefaultMimeMappings;
+import org.springframework.boot.web.server.MimeMappings.Mapping;
+import org.springframework.boot.web.server.MimeMappings.MimeMappingsRuntimeHints;
+import org.springframework.test.util.ReflectionTestUtils;
+
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 
@@ -31,6 +38,7 @@ import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
  * Tests for {@link MimeMappings}.
  *
  * @author Phillip Webb
+ * @author Guirong Hu
  */
 class MimeMappingsTests {
 
@@ -143,4 +151,69 @@ class MimeMappingsTests {
 		assertThat(MimeMappings.DEFAULT).allSatisfy((mapping) -> assertThat(mapping.getMimeType()).matches(pattern));
 	}
 
+	@Test
+	void getCommonTypeOnDefaultMimeMappingsDoesNotLoadMappings() {
+		DefaultMimeMappings mappings = new DefaultMimeMappings();
+		assertThat(mappings.get("json")).isEqualTo("application/json");
+		assertThat((Object) mappings).extracting("loaded").isNull();
+	}
+
+	@Test
+	void getExoticTypeOnDefaultMimeMappingsLoadsMappings() {
+		DefaultMimeMappings mappings = new DefaultMimeMappings();
+		assertThat(mappings.get("123")).isEqualTo("application/vnd.lotus-1-2-3");
+		assertThat((Object) mappings).extracting("loaded").isNotNull();
+	}
+
+	@Test
+	void iterateOnDefaultMimeMappingsLoadsMappings() {
+		DefaultMimeMappings mappings = new DefaultMimeMappings();
+		assertThat(mappings).isNotEmpty();
+		assertThat((Object) mappings).extracting("loaded").isNotNull();
+	}
+
+	@Test
+	void commonMappingsAreSubsetOfAllMappings() {
+		MimeMappings commonMappings = (MimeMappings) ReflectionTestUtils.getField(DefaultMimeMappings.class, "COMMON");
+		for (Mapping commonMapping : commonMappings) {
+			assertThat(MimeMappings.DEFAULT.get(commonMapping.getExtension())).isEqualTo(commonMapping.getMimeType());
+		}
+	}
+
+	@Test
+	void lazyCopyWhenNotMutatedDelegates() {
+		DefaultMimeMappings mappings = new DefaultMimeMappings();
+		MimeMappings lazyCopy = MimeMappings.lazyCopy(mappings);
+		assertThat(lazyCopy.get("json")).isEqualTo("application/json");
+		assertThat((Object) mappings).extracting("loaded").isNull();
+	}
+
+	@Test
+	void lazyCopyWhenMutatedCreatesCopy() {
+		DefaultMimeMappings mappings = new DefaultMimeMappings();
+		MimeMappings lazyCopy = MimeMappings.lazyCopy(mappings);
+		lazyCopy.add("json", "other/json");
+		assertThat(lazyCopy.get("json")).isEqualTo("other/json");
+		assertThat((Object) mappings).extracting("loaded").isNotNull();
+	}
+
+	@Test
+	void lazyCopyWhenMutatedCreatesCopyOnlyOnce() {
+		MimeMappings mappings = new MimeMappings();
+		mappings.add("json", "one/json");
+		MimeMappings lazyCopy = MimeMappings.lazyCopy(mappings);
+		assertThat(lazyCopy.get("json")).isEqualTo("one/json");
+		mappings.add("json", "two/json");
+		lazyCopy.add("json", "other/json");
+		assertThat(lazyCopy.get("json")).isEqualTo("other/json");
+	}
+
+	@Test
+	void shouldRegisterHints() {
+		RuntimeHints runtimeHints = new RuntimeHints();
+		new MimeMappingsRuntimeHints().registerHints(runtimeHints, getClass().getClassLoader());
+		assertThat(RuntimeHintsPredicates.resource()
+				.forResource("org/springframework/boot/web/server/mime-mappings.properties")).accepts(runtimeHints);
+	}
+
 }