Improve error handling

Author: cube

src/main/java/com/chaudhuri/ooliteaddonscanner2/AddonsUtil.java

@@ -369,6 +369,9 @@ public static void readShipModels(ExpansionCache cache, Expansion expansion) {
         if (expansion == null) {
             throw new IllegalArgumentException(EXCEPTION_EXPANSION_MUST_NOT_BE_NULL);
         }
+        if (expansion.getDownloadUrl() == null) {
+            throw new IllegalArgumentException("expansion must have download url");
+        }
 
         try {
             ZipInputStream zin = new ZipInputStream(new BufferedInputStream(cache.getPluginInputStream(expansion.getDownloadUrl())));

src/main/java/com/chaudhuri/ooliteaddonscanner2/ExpansionCache.java

@@ -408,15 +408,19 @@ public void update(String url) throws IOException, MalformedURLException, URISyn
         }
 
         cacheMisses++;
-        doDownload(u, localFile);
+        try {
+            doDownload(u, localFile);
+        } catch (IOException e) {
+            log.info("Could not download {} -> {}", u, localFile, e);
+        }
     }
 
     /**
      * Return the plugin's input stream.
      * If the file is not cached or too old it will be automatically downloaded.
      * 
      * @param url the download url of the file
-     * @return the inputstream (to the cached file on disk)
+     * @return the inputstream (to the cached file on disk), or null if we just do not have it
      * @throws IOException something went wrong
      */
     public InputStream getPluginInputStream(String url) throws IOException, MalformedURLException, URISyntaxException {
@@ -428,7 +432,11 @@ public InputStream getPluginInputStream(String url) throws IOException, Malforme
         update(url);
 
         File cached = getCachedFile(url);
-        return new FileInputStream(cached);
+        if (cached.canRead()) {
+            return new FileInputStream(cached);
+        } else {
+            return null;
+        }
     }
 
     /**

src/test/java/com/chaudhuri/ooliteaddonscanner2/AddonsUtilTest.java

@@ -564,8 +564,13 @@ public void testReadShipModels_ExpansionCache_Expansion3() throws IOException {
         Expansion expansion = new Expansion();
 
         assertEquals(0, expansion.getWarnings().size());
-        AddonsUtil.readShipModels(cache, expansion);
-        assertEquals(1, expansion.getWarnings().size());
+        try {
+            AddonsUtil.readShipModels(cache, expansion);
+            fail("expected exception");
+        } catch (IllegalArgumentException e) {
+            assertEquals("expansion must have download url", e.getMessage());
+            log.debug("caught expected exception", e);
+        }
     }
 
     /**