From 11b1318cad455cb6ce58a0c1e7b98d5a03b369fb Mon Sep 17 00:00:00 2001
From: Phillip Webb <pwebb@pivotal.io>
Date: Thu, 20 Sep 2018 21:26:02 -0700
Subject: [PATCH] Reduce GC pressure in JAR handler

Update the JAR `Hander` so that URL `startsWith` checks produce less
garbage. Comparisons are now performed first on the `path` rather than
the full `toString`. URL `toString` operations produce quite a lot of
garbage since a `StringBuilder` is always used.

In addition, we now also cache the JarFile URL toString to save repeated
calculation.

Closes gh-14561
---
 .../org/springframework/boot/loader/jar/Handler.java   | 10 ++++++++--
 .../org/springframework/boot/loader/jar/JarFile.java   |  9 +++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/Handler.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/Handler.java
index 5e9c8075cd..5b23b677bf 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/Handler.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/Handler.java
@@ -92,8 +92,7 @@ public class Handler extends URLStreamHandler {
 
 	@Override
 	protected URLConnection openConnection(URL url) throws IOException {
-		if (this.jarFile != null
-				&& url.toString().startsWith(this.jarFile.getUrl().toString())) {
+		if (this.jarFile != null && isUrlInJarFile(url, this.jarFile)) {
 			return JarURLConnection.get(url, this.jarFile);
 		}
 		try {
@@ -104,6 +103,13 @@ public class Handler extends URLStreamHandler {
 		}
 	}
 
+	private boolean isUrlInJarFile(URL url, JarFile jarFile)
+			throws MalformedURLException {
+		// Try the path first to save building a new url string each time
+		return url.getPath().startsWith(jarFile.getUrl().getPath())
+				&& url.toString().startsWith(jarFile.getUrlString());
+	}
+
 	private URLConnection openFallbackConnection(URL url, Exception reason)
 			throws IOException {
 		try {
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarFile.java b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarFile.java
index 9c16b0b74d..dafcd4a2b1 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarFile.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/JarFile.java
@@ -69,6 +69,8 @@ public class JarFile extends java.util.jar.JarFile {
 
 	private URL url;
 
+	private String urlString;
+
 	private JarFileEntries entries;
 
 	private Supplier<Manifest> manifestSupplier;
@@ -301,6 +303,13 @@ public class JarFile extends java.util.jar.JarFile {
 		}
 	}
 
+	String getUrlString() throws MalformedURLException {
+		if (this.urlString == null) {
+			this.urlString = getUrl().toString();
+		}
+		return this.urlString;
+	}
+
 	/**
 	 * Return a URL that can be used to access this JAR file. NOTE: the specified URL
 	 * cannot be serialized and or cloned.