diff --git a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKey.java b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKey.java
index cae978d133c..44df4bc1d9d 100644
--- a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKey.java
+++ b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKey.java
@@ -44,6 +44,14 @@ final class JarFileUrlKey {
 		this.runtimeRef = "runtime".equals(url.getRef());
 	}
 
+	JarFileUrlKey(String protocol, String host, int port, String file, boolean runtimeRef) {
+		this.protocol = protocol;
+		this.host = host;
+		this.port = port;
+		this.file = file;
+		this.runtimeRef = runtimeRef;
+	}
+
 	@Override
 	public boolean equals(Object obj) {
 		if (this == obj) {
diff --git a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarUrlConnection.java b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarUrlConnection.java
index ba6521de5de..0b78cc298e1 100644
--- a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarUrlConnection.java
+++ b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/JarUrlConnection.java
@@ -337,13 +337,19 @@ final class JarUrlConnection extends java.net.JarURLConnection {
 			int separator = spec.indexOf("!/");
 			boolean specHasEntry = (separator != -1) && (separator + 2 != spec.length());
 			if (specHasEntry) {
-				URL jarFileUrl = new URL(spec.substring(0, separator));
-				if ("runtime".equals(url.getRef())) {
-					jarFileUrl = new URL(jarFileUrl, "#runtime");
+				String jarFileSpec = spec.substring(0, separator);
+				boolean runtimeRef = "runtime".equals(url.getRef());
+				JarFileUrlKey urlKey = new JarFileUrlKey("jar", "", -1, jarFileSpec, runtimeRef);
+				JarFile jarFile = jarFiles.getCached(urlKey);
+				if (jarFile == null) {
+					URL jarFileUrl = new URL(jarFileSpec);
+					if (runtimeRef) {
+						jarFileUrl = new URL(jarFileUrl, "#runtime");
+					}
+					jarFile = jarFiles.getOrCreate(true, jarFileUrl);
+					jarFiles.cacheIfAbsent(true, jarFileUrl, jarFile);
 				}
 				String entryName = UrlDecoder.decode(spec.substring(separator + 2));
-				JarFile jarFile = jarFiles.getOrCreate(true, jarFileUrl);
-				jarFiles.cacheIfAbsent(true, jarFileUrl, jarFile);
 				if (!hasEntry(jarFile, entryName)) {
 					return notFoundConnection(jarFile.getName(), entryName);
 				}
diff --git a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/UrlJarFiles.java b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/UrlJarFiles.java
index e2dbb3a29e9..c848d62e1ca 100644
--- a/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/UrlJarFiles.java
+++ b/loader/spring-boot-loader/src/main/java/org/springframework/boot/loader/net/protocol/jar/UrlJarFiles.java
@@ -81,6 +81,15 @@ class UrlJarFiles {
 		return this.cache.get(jarFileUrl);
 	}
 
+	/**
+	 * Return the cached {@link JarFile} if available.
+	 * @param urlKey the jar file URL key
+	 * @return the cached jar or {@code null}
+	 */
+	JarFile getCached(JarFileUrlKey urlKey) {
+		return this.cache.get(urlKey);
+	}
+
 	/**
 	 * Cache the given {@link JarFile} if caching can be used and there is no existing
 	 * entry.
@@ -154,7 +163,15 @@ class UrlJarFiles {
 		 * @return the cached {@link JarFile} or {@code null}
 		 */
 		JarFile get(URL jarFileUrl) {
-			JarFileUrlKey urlKey = new JarFileUrlKey(jarFileUrl);
+			return get(new JarFileUrlKey(jarFileUrl));
+		}
+
+		/**
+		 * Get a {@link JarFile} from the cache given a jar file URL key.
+		 * @param urlKey the jar file URL key
+		 * @return the cached {@link JarFile} or {@code null}
+		 */
+		JarFile get(JarFileUrlKey urlKey) {
 			synchronized (this) {
 				return this.jarFileUrlToJarFile.get(urlKey);
 			}
diff --git a/loader/spring-boot-loader/src/test/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKeyTests.java b/loader/spring-boot-loader/src/test/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKeyTests.java
index 575630819aa..34bb217870b 100644
--- a/loader/spring-boot-loader/src/test/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKeyTests.java
+++ b/loader/spring-boot-loader/src/test/java/org/springframework/boot/loader/net/protocol/jar/JarFileUrlKeyTests.java
@@ -101,4 +101,27 @@ class JarFileUrlKeyTests {
 		return new JarFileUrlKey(new URL(spec));
 	}
 
+	@Test
+	void directKeyEqualsUrlKey() throws Exception {
+		JarFileUrlKey fromUrl = key("jar:nested:/my.jar/!mynested.jar!/my/path");
+		JarFileUrlKey direct = new JarFileUrlKey("jar", "", -1, "nested:/my.jar/!mynested.jar!/my/path", false);
+		assertThat(direct).isEqualTo(fromUrl);
+		assertThat(direct.hashCode()).isEqualTo(fromUrl.hashCode());
+	}
+
+	@Test
+	void directKeyWithRuntimeRefEqualsUrlKey() throws Exception {
+		JarFileUrlKey fromUrl = key("jar:nested:/my.jar/!mynested.jar!/my/path#runtime");
+		JarFileUrlKey direct = new JarFileUrlKey("jar", "", -1, "nested:/my.jar/!mynested.jar!/my/path", true);
+		assertThat(direct).isEqualTo(fromUrl);
+		assertThat(direct.hashCode()).isEqualTo(fromUrl.hashCode());
+	}
+
+	@Test
+	void directKeyWithRuntimeRefNotEqualToKeyWithout() {
+		JarFileUrlKey k1 = new JarFileUrlKey("jar", "", -1, "nested:/my.jar/!mynested.jar!/my/path", true);
+		JarFileUrlKey k2 = new JarFileUrlKey("jar", "", -1, "nested:/my.jar/!mynested.jar!/my/path", false);
+		assertThat(k1).isNotEqualTo(k2);
+	}
+
 }