java/src/main/com/google/appengine/tools/development/agent/AppEngineDevAgent.java

   1 // Copyright 2009 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.tools.development.agent;
   4
   5 import java.io.File;
   6 import java.lang.instrument.Instrumentation;
   7 import java.lang.reflect.Method;
   8 import java.net.MalformedURLException;
   9 import java.net.URISyntaxException;
  10 import java.net.URL;
  11 import java.net.URLClassLoader;
  12 import java.security.AllPermission;
  13 import java.security.CodeSource;
  14 import java.security.PermissionCollection;
  15 import java.util.logging.Level;
  16 import java.util.logging.Logger;
  17
  18 /**
  19  * An instrumentation agent for the dev_appserver. Implements whitelisting and any
  20  * other facilities that require instrumentation.
  21  *
  22  */
  23 public class AppEngineDevAgent {
  24
  25   private static final String AGENT_IMPL =
  26       "com.google.appengine.tools.development.agent.impl.AgentImpl";
  27
  28   private static final String AGENT_IMPL_JAR = "appengine-agentimpl.jar";
  29
  30   private static final String AGENT_DIR_PROP = "appengine-agent-dir";
  31
  32   private static final Logger logger = Logger.getLogger(AppEngineDevAgent.class.getName());
  33
  34   private static Object impl;
  35
  36   public static void premain(String agentArgs, Instrumentation inst) {
  37
  38     URL agentImplLib = findAgentImplLib();
  39     URLClassLoader agentImplLoader = new URLClassLoader(new URL[] {agentImplLib}) {
  40       @Override
  41       protected PermissionCollection getPermissions(CodeSource codesource) {
  42         PermissionCollection perms = super.getPermissions(codesource);
  43         perms.add(new AllPermission());
  44         return perms;
  45       }
  46     };
  47     try {
  48       Class<?> implClass = agentImplLoader.loadClass(AGENT_IMPL);
  49       Method getInstance = implClass.getMethod("getInstance");
  50       impl = getInstance.invoke(null);
  51       Method run = implClass.getMethod("run", Instrumentation.class, boolean.class);
  52       run.invoke(impl, inst, treatRestrictedClassListViolationsAsErrors(agentArgs));
  53     } catch (Exception e) {
  54       logger.log(Level.SEVERE, "Unable to load the App Engine dev agent. Security restrictions " +
  55           "will not be completely emulated.", e);
  56     }
  57   }
  58
  59   private static boolean treatRestrictedClassListViolationsAsErrors(String agentArgs) {
  60     return "treatRestrictedClassListViolationsAsErrors=true".equals(agentArgs);
  61   }
  62
  63   /**
  64    * Returns the agent implementation, which is loaded in its own ClassLoader.
  65    * The Agent structurally conforms to the {@link Agent Agent} interface.
  66    */
  67   public static Object getAgent() {
  68     return impl;
  69   }
  70
  71   private static URL findAgentImplLib() {
  72
  73     URL codeLocation = AppEngineDevAgent.class.getProtectionDomain().getCodeSource().getLocation();
  74     File agentDir;
  75
  76     String agentDirFromSysProps = System.getProperty(AGENT_DIR_PROP);
  77     if (agentDirFromSysProps != null) {
  78       agentDir = new File(agentDirFromSysProps);
  79     } else {
  80       try {
  81         agentDir = new File(codeLocation.toURI());
  82       } catch (URISyntaxException e) {
  83         agentDir = new File(codeLocation.getFile());
  84       }
  85
  86       agentDir = agentDir.getParentFile();
  87     }
  88     if (!agentDir.isDirectory()) {
  89       throw new RuntimeException(
  90           "Unable to find agent directory at " + agentDir.getAbsolutePath());
  91     }
  92
  93     File agentImplLib = new File(agentDir, AGENT_IMPL_JAR);
  94
  95     if (!agentImplLib.exists()) {
  96       throw new RuntimeException("Unable to find " + AGENT_IMPL_JAR + " in " +
  97           agentDir.getAbsolutePath());
  98     }
  99
 100     try {
 101       return agentImplLib.toURI().toURL();
 102     } catch (MalformedURLException e) {
 103       throw new RuntimeException("Unable to retrieve a URL for " + agentImplLib.getAbsolutePath(),
 104           e);
 105     }
 106   }
 107 }