Lookup tools.jar (JDK8) programatically to boost javap performance

AdoptOpenJDK · Feb 27, 2018 · 43ba633 · 43ba633
1 parent 4bda189
commit 43ba633
Showing 1 changed file with 105 additions and 35 deletions.
diff --git a/core/src/main/java/org/adoptopenjdk/jitwatch/process/javap/ReflectionJavap.java b/core/src/main/java/org/adoptopenjdk/jitwatch/process/javap/ReflectionJavap.java
@@ -7,40 +7,110 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.OutputStream;
 import java.lang.reflect.Method;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.List;
 
+import org.adoptopenjdk.jitwatch.loader.DisposableURLClassLoader;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 public class ReflectionJavap
 {
 	private static final Logger logger = LoggerFactory.getLogger(ReflectionJavap.class);
 
-	private static final String JAVAP_CLASS = "com.sun.tools.javap.JavapTask";
+	private static final String JAVAPTASK_CLASS = "com.sun.tools.javap.JavapTask";
 
 	private static final int BUFFER_SIZE = 64 * 1024;
-
+
-	public static boolean canUseReflectionJavap()
+	private static boolean hasCheckedForToolsJar = false;
+
+	private static Boolean canUseReflectionJavap = null;
+
+	private static Class<?> classJavapTask;
+
+	private static URL locateToolsJar()
 	{
-		boolean available = false;
+		Path javaHome = Paths.get(System.getProperty("java.home"));
+
+		Path toolsJarPath = Paths.get(javaHome.toString(), "..", "lib", "tools.jar").normalize();
 
-		try
+		URL result = null;
+
+		if (toolsJarPath.toFile().exists())
 		{
-			Class<?> javapClass = Class.forName(JAVAP_CLASS);
+			try
-
+			{
-			javapClass.getMethod("setLog", new Class[] { OutputStream.class });
+				result = toolsJarPath.toFile().toURI().toURL();
-			javapClass.getMethod("handleOptions", new Class[] { String[].class });
+			}
-			javapClass.getMethod("call", new Class[] {});
+			catch (MalformedURLException e)
-
+			{
-			available = true;
+				e.printStackTrace();
+			}
 		}
-		catch (ClassNotFoundException | NoSuchMethodException | SecurityException e)
+
+		return result;
+	}
+
+	public static boolean canUseReflectionJavap()
+	{
+		if (canUseReflectionJavap == null)
 		{
+			boolean available = false;
+
+			try
+			{
+				classJavapTask = Class.forName(JAVAPTASK_CLASS);
+			}
+			catch (ClassNotFoundException cnfe)
+			{
+				URL toolsJarURL = locateToolsJar();
+
+				if (toolsJarURL != null)
+				{
+					List<URL> urls = new ArrayList<>();
+
+					urls.add(toolsJarURL);
+
+					DisposableURLClassLoader disposableClassLoader = new DisposableURLClassLoader(urls);
+
+					try
+					{
+						classJavapTask = Class.forName(JAVAPTASK_CLASS, false, disposableClassLoader);
+					}
+					catch (ClassNotFoundException cnfe2)
+					{
+						cnfe2.printStackTrace();
+					}
+				}
+			}
+
+			if (classJavapTask != null)
+			{
+				try
+				{
+					classJavapTask.getMethod("setLog", new Class[] { OutputStream.class });
+					classJavapTask.getMethod("handleOptions", new Class[] { String[].class });
+					classJavapTask.getMethod("call", new Class[] {});
+
+					available = true;
+				}
+				catch (NoSuchMethodException | SecurityException e)
+				{
+					e.printStackTrace();
+				}
+			}
+
+			canUseReflectionJavap = new Boolean(available);
 		}
 
-		return available;
+		return canUseReflectionJavap.booleanValue();
 	}
 
 	public static String getBytecode(List<String> classLocations, String fqClassName)
@@ -55,31 +125,31 @@ public static String getBytecode(List<String> classLocations, String fqClassName
 	private static String createJavapTaskFromArguments(String fqClassName, String[] args)
 	{
 		String byteCodeString = null;
-
+		
-		try
+		if (classJavapTask != null)
 		{
-			Class<?> javapClass = Class.forName(JAVAP_CLASS);
+			try
-
-			Object javapObject = javapClass.newInstance();
-
-			Method methodSetLog = javapClass.getMethod("setLog", new Class[] { OutputStream.class });
-			Method methodHandleOptions = javapClass.getMethod("handleOptions", new Class[] { String[].class });
-			Method methodCall = javapClass.getMethod("call", new Class[] {});
-
-			try (ByteArrayOutputStream baos = new ByteArrayOutputStream(BUFFER_SIZE))
 			{
-				methodSetLog.invoke(javapObject, baos);
+				Object javapObject = classJavapTask.newInstance();
-				methodHandleOptions.invoke(javapObject, new Object[] {args});
+
-				methodCall.invoke(javapObject);
+				Method methodSetLog = classJavapTask.getMethod("setLog", new Class[] { OutputStream.class });
-
+				Method methodHandleOptions = classJavapTask.getMethod("handleOptions", new Class[] { String[].class });
-				byteCodeString = baos.toString();
+				Method methodCall = classJavapTask.getMethod("call", new Class[] {});
+
+				try (ByteArrayOutputStream baos = new ByteArrayOutputStream(BUFFER_SIZE))
+				{
+					methodSetLog.invoke(javapObject, baos);
+					methodHandleOptions.invoke(javapObject, new Object[] {args});
+					methodCall.invoke(javapObject);
+
+					byteCodeString = baos.toString();
+				}
+			}
+			catch (Exception e)
+			{
+				logger.error("Could not load bytecode via reflection", e);
 			}
 		}
-		catch (Exception e)
-		{
-			logger.error("Could not load bytecode via reflection", e);
-		}
-
 		return byteCodeString;
 	}