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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      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 
     18 package android.filterfw.core;
     19 
     20 import android.filterfw.core.Filter;
     21 import android.util.Log;
     22 
     23 import dalvik.system.PathClassLoader;
     24 
     25 import java.lang.reflect.Constructor;
     26 import java.lang.ClassLoader;
     27 import java.lang.Thread;
     28 import java.util.HashSet;
     29 
     30 /**
     31  * @hide
     32  */
     33 public class FilterFactory {
     34 
     35     private static FilterFactory mSharedFactory;
     36     private HashSet<String> mPackages = new HashSet<String>();
     37 
     38     private static ClassLoader mCurrentClassLoader;
     39     private static HashSet<String> mLibraries;
     40     private static Object mClassLoaderGuard;
     41 
     42     static {
     43         mCurrentClassLoader = Thread.currentThread().getContextClassLoader();
     44         mLibraries = new HashSet<String>();
     45         mClassLoaderGuard = new Object();
     46     }
     47 
     48     private static final String TAG = "FilterFactory";
     49     private static boolean mLogVerbose = Log.isLoggable(TAG, Log.VERBOSE);
     50 
     51     public static FilterFactory sharedFactory() {
     52         if (mSharedFactory == null) {
     53             mSharedFactory = new FilterFactory();
     54         }
     55         return mSharedFactory;
     56     }
     57 
     58     /**
     59      * Adds a new Java library to the list to be scanned for filters.
     60      * libraryPath must be an absolute path of the jar file.  This needs to be
     61      * static because only one classloader per process can open a shared native
     62      * library, which a filter may well have.
     63      */
     64     public static void addFilterLibrary(String libraryPath) {
     65         if (mLogVerbose) Log.v(TAG, "Adding filter library " + libraryPath);
     66         synchronized(mClassLoaderGuard) {
     67             if (mLibraries.contains(libraryPath)) {
     68                 if (mLogVerbose) Log.v(TAG, "Library already added");
     69                 return;
     70             }
     71             mLibraries.add(libraryPath);
     72             // Chain another path loader to the current chain
     73             mCurrentClassLoader = new PathClassLoader(libraryPath, mCurrentClassLoader);
     74         }
     75     }
     76 
     77     public void addPackage(String packageName) {
     78         if (mLogVerbose) Log.v(TAG, "Adding package " + packageName);
     79         /* TODO: This should use a getPackage call in the caller's context, but no such method exists.
     80         Package pkg = Package.getPackage(packageName);
     81         if (pkg == null) {
     82             throw new IllegalArgumentException("Unknown filter package '" + packageName + "'!");
     83         }
     84         */
     85         mPackages.add(packageName);
     86     }
     87 
     88     public Filter createFilterByClassName(String className, String filterName) {
     89         if (mLogVerbose) Log.v(TAG, "Looking up class " + className);
     90         Class filterClass = null;
     91 
     92         // Look for the class in the imported packages
     93         for (String packageName : mPackages) {
     94             try {
     95                 if (mLogVerbose) Log.v(TAG, "Trying "+packageName + "." + className);
     96                 synchronized(mClassLoaderGuard) {
     97                     filterClass = mCurrentClassLoader.loadClass(packageName + "." + className);
     98                 }
     99             } catch (ClassNotFoundException e) {
    100                 continue;
    101             }
    102             // Exit loop if class was found.
    103             if (filterClass != null) {
    104                 break;
    105             }
    106         }
    107         if (filterClass == null) {
    108             throw new IllegalArgumentException("Unknown filter class '" + className + "'!");
    109         }
    110         return createFilterByClass(filterClass, filterName);
    111     }
    112 
    113     public Filter createFilterByClass(Class filterClass, String filterName) {
    114         // Make sure this is a Filter subclass
    115         try {
    116             filterClass.asSubclass(Filter.class);
    117         } catch (ClassCastException e) {
    118             throw new IllegalArgumentException("Attempting to allocate class '" + filterClass
    119                 + "' which is not a subclass of Filter!");
    120         }
    121 
    122         // Look for the correct constructor
    123         Constructor filterConstructor = null;
    124         try {
    125             filterConstructor = filterClass.getConstructor(String.class);
    126         } catch (NoSuchMethodException e) {
    127             throw new IllegalArgumentException("The filter class '" + filterClass
    128                 + "' does not have a constructor of the form <init>(String name)!");
    129         }
    130 
    131         // Construct the filter
    132         Filter filter = null;
    133         try {
    134             filter = (Filter)filterConstructor.newInstance(filterName);
    135         } catch (Throwable t) {
    136             // Condition checked below
    137         }
    138 
    139         if (filter == null) {
    140             throw new IllegalArgumentException("Could not construct the filter '"
    141                 + filterName + "'!");
    142         }
    143         return filter;
    144     }
    145 }
    146