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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Eclipse Public License, Version 1.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.eclipse.org/org/documents/epl-v10.php
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.ide.eclipse.adt.internal.editors.layout.gre;
     18 
     19 import com.android.ide.common.api.IViewRule;
     20 import com.android.ide.eclipse.adt.AdtPlugin;
     21 import com.android.ide.eclipse.adt.internal.sdk.ProjectState;
     22 import com.android.ide.eclipse.adt.internal.sdk.Sdk;
     23 import com.android.sdklib.internal.project.ProjectProperties;
     24 import com.android.utils.Pair;
     25 
     26 import org.eclipse.core.resources.IProject;
     27 import org.eclipse.core.runtime.CoreException;
     28 import org.eclipse.core.runtime.IStatus;
     29 import org.eclipse.core.runtime.QualifiedName;
     30 
     31 import java.io.File;
     32 import java.net.MalformedURLException;
     33 import java.net.URL;
     34 import java.net.URLClassLoader;
     35 import java.util.ArrayList;
     36 import java.util.List;
     37 
     38 /**
     39  * The {@link RuleLoader} is responsible for loading (and unloading)
     40  * {@link IViewRule} classes. There is typically one {@link RuleLoader}
     41  * per project.
     42  */
     43 public class RuleLoader {
     44     /**
     45      * Qualified name for the per-project non-persistent property storing the
     46      * {@link RuleLoader} for this project
     47      */
     48     private final static QualifiedName RULE_LOADER = new QualifiedName(AdtPlugin.PLUGIN_ID,
     49             "ruleloader"); //$NON-NLS-1$
     50 
     51     private final IProject mProject;
     52     private ClassLoader mUserClassLoader;
     53     private List<Pair<File, Long>> mUserJarTimeStamps;
     54     private long mLastCheckTimeStamp;
     55 
     56     /**
     57      * Flag set when we've attempted to initialize the {@link #mUserClassLoader}
     58      * already
     59      */
     60     private boolean mUserClassLoaderInited;
     61 
     62     /**
     63      * Returns the {@link RuleLoader} for the given project
     64      *
     65      * @param project the project the loader is associated with
     66      * @return an {@RuleLoader} for the given project,
     67      *         never null
     68      */
     69     public static RuleLoader get(IProject project) {
     70         RuleLoader loader = null;
     71         try {
     72             loader = (RuleLoader) project.getSessionProperty(RULE_LOADER);
     73         } catch (CoreException e) {
     74             // Not a problem; we will just create a new one
     75         }
     76         if (loader == null) {
     77             loader = new RuleLoader(project);
     78             try {
     79                 project.setSessionProperty(RULE_LOADER, loader);
     80             } catch (CoreException e) {
     81                 AdtPlugin.log(e, "Can't store RuleLoader");
     82             }
     83         }
     84         return loader;
     85     }
     86 
     87     /** Do not call; use the {@link #get} factory method instead. */
     88     private RuleLoader(IProject project) {
     89         mProject = project;
     90     }
     91 
     92     /**
     93      * Find out whether the given project has 3rd party ViewRules, and if so
     94      * return a ClassLoader which can locate them. If not, return null.
     95      * @param project The project to load user rules from
     96      * @return A class loader which can user view rules, or otherwise null
     97      */
     98     private ClassLoader computeUserClassLoader(IProject project) {
     99         // Default place to locate layout rules. The user may also add to this
    100         // path by defining a config property specifying
    101         // additional .jar files to search via a the layoutrules.jars property.
    102         ProjectState state = Sdk.getProjectState(project);
    103         ProjectProperties projectProperties = state.getProperties();
    104 
    105         // Ensure we have the latest & greatest version of the properties.
    106         // This allows users to reopen editors in a running Eclipse instance
    107         // to get updated view rule jars
    108         projectProperties.reload();
    109 
    110         String path = projectProperties.getProperty(
    111                 ProjectProperties.PROPERTY_RULES_PATH);
    112 
    113         if (path != null && path.length() > 0) {
    114 
    115             mUserJarTimeStamps = new ArrayList<Pair<File, Long>>();
    116             mLastCheckTimeStamp = System.currentTimeMillis();
    117 
    118             List<URL> urls = new ArrayList<URL>();
    119             String[] pathElements = path.split(File.pathSeparator);
    120             for (String pathElement : pathElements) {
    121                 pathElement = pathElement.trim(); // Avoid problems with trailing whitespace etc
    122                 File pathFile = new File(pathElement);
    123                 if (!pathFile.isAbsolute()) {
    124                     pathFile = new File(project.getLocation().toFile(), pathElement);
    125                 }
    126                 // Directories and jar files are okay. Do we need to
    127                 // validate the files here as .jar files?
    128                 if (pathFile.isFile() || pathFile.isDirectory()) {
    129                     URL url;
    130                     try {
    131                         url = pathFile.toURI().toURL();
    132                         urls.add(url);
    133 
    134                         mUserJarTimeStamps.add(Pair.of(pathFile, pathFile.lastModified()));
    135                     } catch (MalformedURLException e) {
    136                         AdtPlugin.log(IStatus.WARNING,
    137                                 "Invalid URL: %1$s", //$NON-NLS-1$
    138                                 e.toString());
    139                     }
    140                 }
    141             }
    142 
    143             if (urls.size() > 0) {
    144                 return new URLClassLoader(urls.toArray(new URL[urls.size()]),
    145                         RulesEngine.class.getClassLoader());
    146             }
    147         }
    148 
    149         return null;
    150     }
    151 
    152     /**
    153      * Return the class loader to use for custom views, or null if no custom
    154      * view rules are registered for the project. Note that this class loader
    155      * can change over time (if the jar files are updated), so callers should be
    156      * prepared to unload previous instances.
    157      *
    158      * @return a class loader to use for custom view rules, or null
    159      */
    160     public ClassLoader getClassLoader() {
    161         if (mUserClassLoader == null) {
    162             // Only attempt to load rule paths once.
    163             // TODO: Check the timestamp on the project.properties file so we can dynamically
    164             // pick up cases where the user edits the path
    165             if (!mUserClassLoaderInited) {
    166                 mUserClassLoaderInited = true;
    167                 mUserClassLoader = computeUserClassLoader(mProject);
    168             }
    169         } else {
    170             // Check the timestamp on the jar files in the custom view path to see if we
    171             // need to reload the classes (but only do this at most every 3 seconds)
    172             if (mUserJarTimeStamps != null) {
    173                 long time = System.currentTimeMillis();
    174                 if (time - mLastCheckTimeStamp > 3000) {
    175                     mLastCheckTimeStamp = time;
    176                     for (Pair<File, Long> pair : mUserJarTimeStamps) {
    177                         File file = pair.getFirst();
    178                         Long prevModified = pair.getSecond();
    179                         long modified = file.lastModified();
    180                         if (prevModified.longValue() != modified) {
    181                             mUserClassLoaderInited = true;
    182                             mUserJarTimeStamps = null;
    183                             mUserClassLoader = computeUserClassLoader(mProject);
    184                         }
    185                     }
    186                 }
    187             }
    188         }
    189 
    190         return mUserClassLoader;
    191     }
    192 }
    193