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 static com.google.apphosting.utils.clearcast.ClearCast.cast;
   6 import static com.google.apphosting.utils.clearcast.ClearCast.staticCast;
   7
   8 import java.io.File;
   9 import java.lang.instrument.Instrumentation;
  10 import java.net.MalformedURLException;
  11 import java.net.URISyntaxException;
  12 import java.net.URL;
  13 import java.net.URLClassLoader;
  14 import java.util.logging.Level;
  15 import java.util.logging.Logger;
  16 import java.security.PermissionCollection;
  17 import java.security.CodeSource;
  18 import java.security.AllPermission;
  19
  20 /**
  21  * An instrumentation agent for the dev_appserver. Implements whitelisting and any
  22  * other facilities that require instrumentation.
  23  *
  24  */
  25 public class AppEngineDevAgent {
  26
  27   private static final String AGENT_IMPL =
  28       "com.google.appengine.tools.development.agent.impl.AgentImpl";
  29
  30   private static final String AGENT_IMPL_JAR = "appengine-agentimpl.jar";
  31
  32   private static final String AGENT_DIR_PROP = "appengine-agent-dir";
  33
  34   private static final Logger logger = Logger.getLogger(AppEngineDevAgent.class.getName());
  35
  36   private static Object impl;
  37
  38   interface AgentImplStruct {
  39     void run(Instrumentation instrumentation, boolean treatRestrictedClassListViolationsAsErrors); Object getInstance();
  40   }
  41
  42   public static void premain(String agentArgs, Instrumentation inst) {
  43
  44     URL agentImplLib = findAgentImplLib();
  45     URLClassLoader agentImplLoader = new URLClassLoader(new URL[] {agentImplLib}) {
  46       @Override
  47       protected PermissionCollection getPermissions(CodeSource codesource) {
  48         PermissionCollection perms = super.getPermissions(codesource);
  49         perms.add(new AllPermission());
  50         return perms;
  51       }
  52     };
  53     try {
  54       Class<?> implClass = agentImplLoader.loadClass(AGENT_IMPL);
  55       impl = staticCast(implClass, AgentImplStruct.class).getInstance();
  56       AgentImplStruct agentImplStruct = cast(impl, AgentImplStruct.class);
  57       agentImplStruct.run(inst, treatRestrictedClassListViolationsAsErrors(agentArgs));
  58     } catch (Exception e) {
  59       logger.log(Level.SEVERE, "Unable to load the App Engine dev agent. Security restrictions " +
  60           "will not be completely emulated.", e);
  61     }
  62   }
  63
  64   private static boolean treatRestrictedClassListViolationsAsErrors(String agentArgs) {
  65     return "treatRestrictedClassListViolationsAsErrors=true".equals(agentArgs);
  66   }
  67
  68   /**
  69    * Returns the agent implementation, which is loaded in its own ClassLoader.
  70    * The Agent structurally conforms to the {@link Agent Agent} interface.
  71    */
  72   public static Object getAgent() {
  73     return impl;
  74   }
  75
  76   private static URL findAgentImplLib() {
  77
  78     URL codeLocation = AppEngineDevAgent.class.getProtectionDomain().getCodeSource().getLocation();
  79     File agentDir;
  80
  81     String agentDirFromSysProps = System.getProperty(AGENT_DIR_PROP);
  82     if (agentDirFromSysProps != null) {
  83       agentDir = new File(agentDirFromSysProps);
  84     } else {
  85       try {
  86         agentDir = new File(codeLocation.toURI());
  87       } catch (URISyntaxException e) {
  88         agentDir = new File(codeLocation.getFile());
  89       }
  90
  91       agentDir = agentDir.getParentFile();
  92     }
  93     if (!agentDir.isDirectory()) {
  94       throw new RuntimeException(
  95           "Unable to find agent directory at " + agentDir.getAbsolutePath());
  96     }
  97
  98     File agentImplLib = new File(agentDir, AGENT_IMPL_JAR);
  99
 100     if (!agentImplLib.exists()) {
 101       throw new RuntimeException("Unable to find " + AGENT_IMPL_JAR + " in " +
 102           agentDir.getAbsolutePath());
 103     }
 104
 105     try {
 106       return agentImplLib.toURI().toURL();
 107     } catch (MalformedURLException e) {
 108       throw new RuntimeException("Unable to retrieve a URL for " + agentImplLib.getAbsolutePath(),
 109           e);
 110     }
 111   }
 112 }