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      1 /*
      2  * Copyright (C) 2010 Google Inc.
      3  *
      4  * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
      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 org.clearsilver.jni;
     18 
     19 import java.io.File;
     20 import java.util.regex.Pattern;
     21 
     22 /**
     23  * Loads the ClearSilver JNI library.
     24  *
     25  * <p>By default, it attempts to load the library 'clearsilver-jni' from the
     26  * path specified in the 'java.library.path' system property. However, this
     27  * can be overriden by calling {@link #setLibraryName(String)} and
     28  * {@link #setLibrarySearchPaths(String[])}.</p>
     29  *
     30  * <p>If this fails, the JVM exits with a code of 1. However, this strategy
     31  * can be changed using {@link #setFailureCallback(Runnable)}.</p>
     32  */
     33 public final class JNI {
     34 
     35   /**
     36    * Failure callback strategy that writes a message to sysout, then calls
     37    * System.exit(1).
     38    */
     39   public static Runnable EXIT_JVM = new Runnable() {
     40     public void run() {
     41       System.err.println("Could not load '" + libraryName + "'. Searched:");
     42       String platformLibraryName = System.mapLibraryName(libraryName);
     43       for (String path : librarySearchPaths) {
     44         System.err.println("  " +
     45             new File(path, platformLibraryName).getAbsolutePath());
     46       }
     47       System.err.println(
     48           "Try specifying -Djava.library.path=[directory] or calling "
     49               + JNI.class.getName() + ".setLibrarySearchPaths(String...)");
     50       System.exit(1);
     51     }
     52   };
     53 
     54   /**
     55    * Failure callback strategy that throws an UnsatisfiedLinkError, which
     56    * should be caught be client code.
     57    */
     58   public static Runnable THROW_ERROR = new Runnable() {
     59     public void run() {
     60       throw new UnsatisfiedLinkError("Could not load '" + libraryName + "'");
     61     }
     62   };
     63 
     64   private static Runnable failureCallback = EXIT_JVM;
     65 
     66   private static Object callbackLock = new Object();
     67 
     68   private static String libraryName = "clearsilver-jni";
     69 
     70   private static String[] librarySearchPaths
     71       = System.getProperty("java.library.path", ".").split(
     72           Pattern.quote(File.pathSeparator));
     73 
     74   private static volatile boolean successfullyLoadedLibrary;
     75 
     76   /**
     77    * Attempts to load the ClearSilver JNI library.
     78    *
     79    * @see #setFailureCallback(Runnable)
     80    */
     81   public static void loadLibrary() {
     82 
     83     // Library already loaded? Great - nothing to do.
     84     if (successfullyLoadedLibrary) {
     85       return;
     86     }
     87 
     88     synchronized (callbackLock) {
     89 
     90       // Search librarySearchPaths...
     91       String platformLibraryName = System.mapLibraryName(libraryName);
     92       for (String path : librarySearchPaths) {
     93         try {
     94           // Attempt to load the library in that path.
     95           System.load(new File(path, platformLibraryName).getAbsolutePath());
     96           // If we got here, it worked. We're done.
     97           successfullyLoadedLibrary = true;
     98           return;
     99         } catch (UnsatisfiedLinkError e) {
    100           // Library not found. Continue loop.
    101         }
    102       }
    103 
    104       // Still here? Couldn't load library. Fail.
    105       if (failureCallback != null) {
    106         failureCallback.run();
    107       }
    108     }
    109 
    110   }
    111 
    112   /**
    113    * Sets a callback for what should happen if the JNI library cannot
    114    * be loaded. The default is {@link #EXIT_JVM}.
    115    *
    116    * @see #EXIT_JVM
    117    * @see #THROW_ERROR
    118    */
    119   public static void setFailureCallback(Runnable failureCallback) {
    120     synchronized(callbackLock) {
    121       JNI.failureCallback = failureCallback;
    122     }
    123   }
    124 
    125   /**
    126    * Set name of JNI library to load. Default is 'clearsilver-jni'.
    127    */
    128   public static void setLibraryName(String libraryName) {
    129     JNI.libraryName = libraryName;
    130   }
    131 
    132   /**
    133    * Sets locations where JNI library is searched.
    134    */
    135   public static void setLibrarySearchPaths(String... paths) {
    136     JNI.librarySearchPaths = paths;
    137   }
    138 
    139 }
    140