Allow per context TLD skip patterns

Change TomcatEmbeddedServletContainerFactory to allow per context
skip patterns to be defined, rather than using a global system property.

This commit also renames `skipPatterns` to `tldSkip` to align it with
Tomcat context.xml configuration.

Updates gh-256

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/CustomSkipPatternJarScanner.java

+/*
+ * Copyright 2012-2014 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.embedded.tomcat;
+
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
+import java.util.StringTokenizer;
+
+import javax.servlet.ServletContext;
+
+import org.apache.tomcat.JarScanner;
+import org.apache.tomcat.JarScannerCallback;
+import org.springframework.util.Assert;
+
+/**
+ * {@link JarScanner} decorator allowing alternative default jar pattern matching.
+ * 
+ * @author Phillip Webb
+ * @see #apply(TomcatEmbeddedContext, String)
+ */
+class SkipPatternJarScanner implements JarScanner {
+
+	private final JarScanner jarScanner;
+
+	private final SkipPattern pattern;
+
+	SkipPatternJarScanner(JarScanner jarScanner, String pattern) {
+		Assert.notNull(jarScanner, "JarScanner must not be null");
+		this.jarScanner = jarScanner;
+		this.pattern = (pattern == null ? new SkipPattern() : new SkipPattern(pattern));
+	}
+
+	@Override
+	public void scan(ServletContext context, ClassLoader classloader,
+			JarScannerCallback callback, Set<String> jarsToSkip) {
+		this.jarScanner.scan(context, classloader, callback,
+				(jarsToSkip == null ? this.pattern.asSet() : jarsToSkip));
+	}
+
+	/**
+	 * Apply this decorator the specified context.
+	 * @param context the context to apply to
+	 * @param pattern the jar skip pattern or {@code null} for defaults
+	 */
+	public static void apply(TomcatEmbeddedContext context, String pattern) {
+		context.setJarScanner(new SkipPatternJarScanner(context.getJarScanner(), pattern));
+	}
+
+	private static class SkipPattern {
+
+		private Set<String> patterns = new LinkedHashSet<String>();
+
+		protected SkipPattern() {
+			add("ant-*.jar");
+			add("aspectj*.jar");
+			add("commons-beanutils*.jar");
+			add("commons-codec*.jar");
+			add("commons-collections*.jar");
+			add("commons-dbcp*.jar");
+			add("commons-digester*.jar");
+			add("commons-fileupload*.jar");
+			add("commons-httpclient*.jar");
+			add("commons-io*.jar");
+			add("commons-lang*.jar");
+			add("commons-logging*.jar");
+			add("commons-math*.jar");
+			add("commons-pool*.jar");
+			add("geronimo-spec-jaxrpc*.jar");
+			add("h2*.jar");
+			add("hamcrest*.jar");
+			add("hibernate*.jar");
+			add("jmx*.jar");
+			add("jmx-tools-*.jar");
+			add("jta*.jar");
+			add("junit-*.jar");
+			add("httpclient*.jar");
+			add("log4j-*.jar");
+			add("mail*.jar");
+			add("org.hamcrest*.jar");
+			add("slf4j*.jar");
+			add("tomcat-embed-core-*.jar");
+			add("tomcat-embed-logging-*.jar");
+			add("tomcat-jdbc-*.jar");
+			add("tomcat-juli-*.jar");
+			add("tools.jar");
+			add("wsdl4j*.jar");
+			add("xercesImpl-*.jar");
+			add("xmlParserAPIs-*.jar");
+			add("xml-apis-*.jar");
+		}
+
+		public SkipPattern(String patterns) {
+			StringTokenizer tokenizer = new StringTokenizer(patterns, ",");
+			while (tokenizer.hasMoreElements()) {
+				add(tokenizer.nextToken());
+			}
+		}
+
+		protected void add(String patterns) {
+			Assert.notNull(patterns, "Patterns must not be null");
+			if (patterns.length() > 0 && !patterns.trim().startsWith(",")) {
+				this.patterns.add(",");
+			}
+			this.patterns.add(patterns);
+		}
+
+		public Set<String> asSet() {
+			return Collections.unmodifiableSet(this.patterns);
+		}
+
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainerFactory.java

@@ -89,14 +89,7 @@ public class TomcatEmbeddedServletContainerFactory extends
 
 	private String protocol = DEFAULT_PROTOCOL;
 
-	private static String DEFAULT_SKIP_JARS = "tomcat-embed-core-*.jar,tomcat-embed-logging-*.jar,tomcat-juli-*.jar,tomcat-jdbc-*.jar,"
-			+ "tools.jar,commons-beanutils*.jar,commons-codec*.jar,commons-collections*.jar,"
-			+ "commons-dbcp*.jar,commons-digester*.jar,commons-fileupload*.jar,commons-httpclient*.jar,commons-io*.jar,commons-lang*.jar,"
-			+ "commons-logging*.jar,commons-math*.jar,commons-pool*.jar,geronimo-spec-jaxrpc*.jar,wsdl4j*.jar,ant-*.jar,"
-			+ "aspectj*.jar,jmx*.jar,h2*.jar,hibernate*.jar,httpclient*.jar,jmx-tools-*.jar,jta*.jar,log4j-*.jar,mail*.jar,slf4j*.jar,"
-			+ "xercesImpl-*.jar,xmlParserAPIs-*.jar,xml-apis-*.jar,junit-*.jar,hamcrest*.jar,org.hamcrest*.jar";
-
-	private String skipJars = DEFAULT_SKIP_JARS;
+	private String tldSkip;
 
 	/**
 	 * Create a new {@link TomcatEmbeddedServletContainerFactory} instance.
@@ -146,7 +139,6 @@ public class TomcatEmbeddedServletContainerFactory extends
 	protected void prepareContext(Host host, ServletContextInitializer[] initializers) {
 		File docBase = getValidDocumentRoot();
 		docBase = (docBase != null ? docBase : createTempDir("tomcat-docbase"));
-		applySkipJars();
 		TomcatEmbeddedContext context = new TomcatEmbeddedContext();
 		context.setName(getContextPath());
 		context.setPath(getContextPath());
@@ -154,6 +146,7 @@ public class TomcatEmbeddedServletContainerFactory extends
 		context.addLifecycleListener(new FixContextListener());
 		context.setParentClassLoader(this.resourceLoader != null ? this.resourceLoader
 				.getClassLoader() : ClassUtils.getDefaultClassLoader());
+		SkipPatternJarScanner.apply(context, this.tldSkip);
 		WebappLoader loader = new WebappLoader(context.getParentClassLoader());
 		loader.setLoaderClass(TomcatEmbeddedWebappClassLoader.class.getName());
 		loader.setDelegate(true);
@@ -173,14 +166,6 @@ public class TomcatEmbeddedServletContainerFactory extends
 		postProcessContext(context);
 	}
 
-	private void applySkipJars() {
-		// Tomcat 8.0
-		System.setProperty("tomcat.util.scan.StandardJarScanFilter.jarsToSkip",
-				this.skipJars);
-		// Tomcat 7.0
-		System.setProperty("tomcat.util.scan.DefaultJarScanner.jarsToSkip", this.skipJars);
-	}
-
 	private void addDefaultServlet(Context context) {
 		Wrapper defaultServlet = context.createWrapper();
 		defaultServlet.setName("default");
@@ -302,11 +287,11 @@ public class TomcatEmbeddedServletContainerFactory extends
 	/**
 	 * A comma-separated list of jars to ignore for TLD scanning. See Tomcat's
 	 * catalina.properties for typical values. Defaults to a list drawn from that source.
-	 * 
-	 * @param skipJars the jars to skip when scanning for tlds etc
+	 * @param tldSkip the jars to skip when scanning for TLDs etc
 	 */
-	public void setSkipJars(String skipJars) {
-		this.skipJars = skipJars;
+	public void setTldSkip(String tldSkip) {
+		Assert.notNull(tldSkip, "TldSkip must not be null");
+		this.tldSkip = tldSkip;
 	}
 
 	/**