Add new setting to disable the classloading cache (#76)

Add support for disabling the JAR file caches in URLClassLoader & Auto-detect if Gradle Daemon is running and set default for disableClassloadingCache setting. This closes #75

src/main/docs/ant-task.html

@@ -87,6 +87,13 @@ <h2>Parameters</h2>
   <td>Reference to a <code>path</code> defined anywhere else. Should be identical to classpath used for compiling the class files.</td>
 </tr>
 
+<tr>
+  <td>disableClassloadingCache</td>
+  <td><code>boolean</code></td>
+  <td><code>false</code></td>
+  <td>Disable the internal JVM classloading cache when getting bytecode from the classpath. This setting slows down checks, but <em>may</em> work around issues with other Mojos, that do not close their class loaders. If you get <code>FileNotFoundException</code>s related to non-existent JAR entries you can try to work around using this setting.</td>
+</tr>
+
 <tr>
   <td>failOnUnsupportedJava</td>
   <td><code>boolean</code></td>

src/main/java/de/thetaphi/forbiddenapis/Checker.java

@@ -60,7 +60,8 @@ public final class Checker implements RelatedClassLookup, Constants {
   public static enum Option {
     FAIL_ON_MISSING_CLASSES,
     FAIL_ON_VIOLATION,
-    FAIL_ON_UNRESOLVABLE_SIGNATURES
+    FAIL_ON_UNRESOLVABLE_SIGNATURES,
+    DISABLE_CLASSLOADING_CACHE
   }
 
   public final boolean isSupportedJDK;
@@ -285,6 +286,9 @@ private ClassSignature getClassFromClassLoader(final String clazz) throws ClassN
       if (url != null) {
         final URLConnection conn = url.openConnection();
         final boolean isRuntimeClass = isRuntimeClass(conn);
+        if (!isRuntimeClass && options.contains(Option.DISABLE_CLASSLOADING_CACHE)) {
+          conn.setUseCaches(false);
+        }
         final InputStream in = conn.getInputStream();
         try {
           classpathClassCache.put(clazz, c = new ClassSignature(AsmUtils.readAndPatchClass(in), isRuntimeClass, false));

src/main/java/de/thetaphi/forbiddenapis/ant/AntTask.java

@@ -71,6 +71,7 @@ public class AntTask extends Task implements Constants {
   private boolean failOnViolation = true;
   private boolean ignoreEmptyFileset = false;
   private String targetVersion = null;
+  private boolean disableClassloadingCache = false;
 
   @Override
   public void execute() throws BuildException {
@@ -109,6 +110,7 @@ public void info(String msg) {
       if (failOnMissingClasses) options.add(FAIL_ON_MISSING_CLASSES);
       if (failOnViolation) options.add(FAIL_ON_VIOLATION);
       if (failOnUnresolvableSignatures) options.add(FAIL_ON_UNRESOLVABLE_SIGNATURES);
+      if (disableClassloadingCache) options.add(DISABLE_CLASSLOADING_CACHE);
       final Checker checker = new Checker(log, loader, options);
 
       if (!checker.isSupportedJDK) {
@@ -380,4 +382,16 @@ public void setFailOnViolation(boolean failOnViolation) {
   public void setTargetVersion(String targetVersion) {
     this.targetVersion = targetVersion;
   }
+
+  /**
+   * Disable the internal JVM classloading cache when getting bytecode from
+   * the classpath. This setting slows down checks, but <em>may</em> work around
+   * issues with other tasks, that do not close their class loaders.
+   * If you get {@code FileNotFoundException}s related to non-existent JAR entries
+   * you can try to work around using this setting.
+   * The default is {@code false}.
+   */
+  public void setDisableClassloadingCache(boolean disableClassloadingCache) {
+    this.disableClassloadingCache = disableClassloadingCache;
+  }
 }

src/main/java/de/thetaphi/forbiddenapis/gradle/CheckForbiddenApis.java

@@ -303,6 +303,27 @@ public void setIgnoreFailures(boolean ignoreFailures) {
     data.ignoreFailures = ignoreFailures;
   }
 
+  /**
+   * Disable the internal JVM classloading cache when getting bytecode from
+   * the classpath. This setting slows down checks, but <em>may</em> work around
+   * issues with other plugin, that do not close their class loaders.
+   * If you get {@code FileNotFoundException}s related to non-existent JAR entries
+   * you can try to work around using this setting.
+   * <p>
+   * The default is {@code false}, unless the plugin detects that your build is
+   * running in the <em>Gradle Daemon</em> (which has this problem), setting the
+   * default to {@code true} as a consequence.
+   */
+  @Input
+  public boolean getDisableClassloadingCache() {
+    return data.disableClassloadingCache;
+  }
+
+  /** @see #getDisableClassloadingCache */
+  public void setDisableClassloadingCache(boolean disableClassloadingCache) {
+    data.disableClassloadingCache = disableClassloadingCache;
+  }
+
   /**
    * List of a custom Java annotations (full class names) that are used in the checked
    * code to suppress errors. Those annotations must have at least
@@ -483,6 +504,7 @@ public void info(String msg) {
       if (getFailOnMissingClasses()) options.add(FAIL_ON_MISSING_CLASSES);
       if (!getIgnoreFailures()) options.add(FAIL_ON_VIOLATION);
       if (getFailOnUnresolvableSignatures()) options.add(FAIL_ON_UNRESOLVABLE_SIGNATURES);
+      if (getDisableClassloadingCache()) options.add(DISABLE_CLASSLOADING_CACHE);
       final Checker checker = new Checker(log, loader, options);
 
       if (!checker.isSupportedJDK) {

src/main/java/de/thetaphi/forbiddenapis/gradle/CheckForbiddenApisExtension.java

@@ -44,7 +44,8 @@ public class CheckForbiddenApisExtension {
     "failOnUnsupportedJava",
     "failOnMissingClasses",
     "failOnUnresolvableSignatures",
-    "ignoreFailures"
+    "ignoreFailures",
+    "disableClassloadingCache"
   );
 
   public FileCollection signaturesFiles; // initialized by plugin-init.groovy
@@ -56,6 +57,7 @@ public class CheckForbiddenApisExtension {
   public boolean failOnUnsupportedJava = false,
     failOnMissingClasses = true,
     failOnUnresolvableSignatures = true,
-    ignoreFailures = false;
+    ignoreFailures = false,
+    disableClassloadingCache = false;
 
 }

src/main/java/de/thetaphi/forbiddenapis/maven/AbstractCheckMojo.java

@@ -155,6 +155,17 @@ public abstract class AbstractCheckMojo extends AbstractMojo implements Constant
   @Parameter(required = false, property="forbiddenapis.failOnViolation", defaultValue = "true")
   private boolean failOnViolation;
 
+  /**
+   * Disable the internal JVM classloading cache when getting bytecode from
+   * the classpath. This setting slows down checks, but <em>may</em> work around
+   * issues with other Mojos, that do not close their class loaders.
+   * If you get {@code FileNotFoundException}s related to non-existent JAR entries
+   * you can try to work around using this setting.
+   * @since 2.0
+   */
+  @Parameter(required = false, defaultValue = "false")
+  private boolean disableClassloadingCache;
+
   /**
    * The default compiler target version used to expand references to bundled JDK signatures.
    * E.g., if you use "jdk-deprecated", it will expand to this version.
@@ -312,6 +323,7 @@ public void info(String msg) {
       if (failOnMissingClasses) options.add(FAIL_ON_MISSING_CLASSES);
       if (failOnViolation) options.add(FAIL_ON_VIOLATION);
       if (failOnUnresolvableSignatures) options.add(FAIL_ON_UNRESOLVABLE_SIGNATURES);
+      if (disableClassloadingCache) options.add(DISABLE_CLASSLOADING_CACHE);
       final Checker checker = new Checker(log, loader, options);
 
       if (!checker.isSupportedJDK) {

src/main/resources/de/thetaphi/forbiddenapis/gradle/plugin-init.groovy

@@ -23,10 +23,19 @@ if (project.plugins.withType(JavaBasePlugin.class).isEmpty()) {
   throw new PluginInstantiationException('Forbidden-apis only works in projects using the java plugin.');
 }
 
+// chck if running in Gradle Daemon?
+// see: http://stackoverflow.com/questions/23265217/how-to-know-whether-you-are-running-inside-a-gradle-daemon
+boolean isGradleDaemon = System.getProperty('sun.java.command', '').startsWith('org.gradle.launcher.daemon.') ||
+  Thread.currentThread().stackTrace.any { it.className.startsWith 'org.gradle.launcher.daemon.' };
+if (isGradleDaemon) {
+  project.logger.info('You are running forbidden-apis in the Gradle Daemon; disabling classloading cache to work around resource leak.');
+}
+
 // create Extension for defaults:
 def extension = project.extensions.create(FORBIDDEN_APIS_EXTENSION_NAME, CheckForbiddenApisExtension.class);
 extension.with {
   signaturesFiles = project.files();
+  disableClassloadingCache |= isGradleDaemon;
 }
 
 // Define our tasks (one for each SourceSet):