util/CachedDatasource.java

   1
   2 package org.de.metux.util;
   3
   4 import java.net.URL;
   5 import java.io.IOException;
   6 import java.util.Hashtable;
   7 import java.io.File;
   8 import java.io.FileNotFoundException;
   9
  10 public class CachedDatasource
  11 {
  12     private Hashtable cache = new Hashtable();
  13     public boolean enabled = true;
  14
  15     public String loadContent(URL url, boolean strip_comments)
  16     {
  17         String filename = url.toString();
  18
  19         if (!enabled)
  20         {
  21             try{
  22                 return LoadFile.load(url,strip_comments);
  23             }
  24             catch (IOException e)
  25             {
  26                 return null;
  27             }
  28         }
  29
  30         String key = "::URL::CONTENT::"+(strip_comments?"STRIP::":"")+url;
  31         String content;
  32
  33         try
  34         {
  35             content = (String)cache.get(key);
  36         }
  37         catch (ClassCastException e)
  38         {
  39             /* we've got an cached NOT-FOUND */
  40             return null;
  41         }
  42
  43         if (content != null)
  44             return content;
  45
  46         try
  47         {
  48             content = LoadFile.load(url,strip_comments);
  49             cache.put(key,content);
  50             return content;
  51         }
  52         catch (IOException e)
  53         {
  54             /* put the error into the cache */
  55             cache.put(key,e);
  56             return null;
  57         }
  58     }
  59
  60     public String loadContent(File filename, boolean strip_comments)
  61     {
  62         if (!enabled)
  63         {
  64             try{
  65                 return LoadFile.load(filename,strip_comments);
  66             }
  67             catch (IOException e)
  68             {
  69                 return null;
  70             }
  71         }
  72
  73         String key = "::FILENAME::CONTENT::"+(strip_comments?"STRIP::":"")+filename;
  74         String content;
  75
  76         try
  77         {
  78             content = (String)cache.get(key);
  79         }
  80         catch (ClassCastException e)
  81         {
  82             /* we've got an cached NOT-FOUND */
  83             return null;
  84         }
  85
  86         if (content != null)
  87             return content;
  88
  89         try
  90         {
  91             content = LoadFile.load(filename,strip_comments);
  92             if (content==null)
  93                 throw new RuntimeException("Could not load file: "+filename);
  94             cache.put(key,content);
  95             return content;
  96         }
  97         catch (IOException e)
  98         {
  99             /* put the error into the cache */
 100             cache.put(key,e);
 101             return null;
 102         }
 103     }
 104
 105     public Hashtable loadTextTable(String fn, String pkey)
 106     {
 107         Hashtable ht;
 108         String key = "::FILENAME::TEXTDB::["+pkey+"]"+fn;
 109
 110         if (!enabled)
 111             return TextTable.Load(fn,pkey);
 112
 113         try
 114         {
 115             ht = (Hashtable)cache.get(key);
 116             if (ht!=null)
 117                 return ht;
 118         }
 119         catch (ClassCastException e)
 120         {
 121             return null;
 122         }
 123
 124         ht = TextTable.Load(fn,pkey);
 125         if (ht==null)
 126         {
 127             cache.put(key,new FileNotFoundException(fn));
 128             return null;
 129         }
 130
 131         cache.put(key,ht);
 132         return ht;
 133     }
 134 }