[FOP-1608] [PATCH] Synchronization fault in FontInfoFinder

• Type: Bug
• Status: Open
• Resolution: Unresolved
• Affects Version/s: 2.5
• Component/s: font/unqualified
• Environment: Operating System: All; Platform: All
• External issue ID: 46336
• Assignee: Unassigned
• Reporter: ilj
• Created: 04/Dec/08 01:12
• Updated: 22/Feb/17 15:31

Description

I have a multi-threaded rendering application. It produced this exception:

java.lang.NullPointerException
at org.apache.fop.fonts.autodetect.FontInfoFinder.find(FontInfoFinder.java:172)
at org.apache.fop.render.PrintRendererConfigurator.addFontInfoListFromFileList(PrintRendererConfigurator.java:233)
at org.apache.fop.render.PrintRendererConfigurator.buildFontListFromConfiguration(PrintRendererConfigurator.java:140)
at org.apache.fop.render.PrintRendererConfigurator.configure(PrintRendererConfigurator.java:95)
at org.apache.fop.render.pdf.PDFRendererConfigurator.configure(PDFRendererConfigurator.java:71)
at org.apache.fop.render.RendererFactory.createRenderer(RendererFactory.java:187)
at org.apache.fop.area.RenderPagesModel.<init>(RenderPagesModel.java:68)
at org.apache.fop.area.AreaTreeHandler.setupModel(AreaTreeHandler.java:127)
at org.apache.fop.area.AreaTreeHandler.<init>(AreaTreeHandler.java:102)
at org.apache.fop.render.RendererFactory.createFOEventHandler(RendererFactory.java:224)
at org.apache.fop.fo.FOTreeBuilder.<init>(FOTreeBuilder.java:100)
at org.apache.fop.apps.Fop.createDefaultHandler(Fop.java:100)
at org.apache.fop.apps.Fop.<init>(Fop.java:78)
at org.apache.fop.apps.FopFactory.newFop(FopFactory.java:247)
...

I guess the problem is, that you don't synchronize usage of FontCache in this method:

150 public EmbedFontInfo find(URL fontUrl, FontResolver resolver, FontCache fontCache) {
151 String embedUrl = null;
152 embedUrl = fontUrl.toExternalForm();
153
154 long fileLastModified = -1;
155 if (fontCache != null) {
156 try {
157 URLConnection conn = fontUrl.openConnection();
158 try

{ 159 fileLastModified = conn.getLastModified(); 160 }

finally

{ 161 //An InputStream is created even if it's not accessed, but we need to close it. 162 IOUtils.closeQuietly(conn.getInputStream()); 163 }

164 } catch (IOException e)

{ 165 // Should never happen, because URL must be local 166 log.debug("IOError: " + e.getMessage()); 167 fileLastModified = 0; 168 }

169 // firstly try and fetch it from cache before loading/parsing the font file
170 if (fontCache.containsFont(embedUrl)) {
171 CachedFontInfo fontInfo = fontCache.getFont(embedUrl);
172 if (fontInfo.lastModified() == fileLastModified)

{ 173 return fontInfo; 174 }

else

{ 175 // out of date cache item 176 fontCache.removeFont(embedUrl); 177 }

178 // is this a previously failed parsed font?
179 } else if (fontCache.isFailedFont(embedUrl, fileLastModified)) {
180 if (log.isDebugEnabled())

{ 181 log.debug("Skipping font file that failed to load previously: " + embedUrl); 182 }

183 return null;
184 }
185 }
186
187 // try to determine triplet information from font file
188 CustomFont customFont = null;
189 try

{ 190 customFont = FontLoader.loadFont(fontUrl, resolver); 191 }

catch (Exception e) {
192 //TODO Too verbose (it's an error but we don't care if some fonts can't be loaded)
193 if (log.isErrorEnabled())

{ 194 log.error("Unable to load font file: " + embedUrl + ". Reason: " + e.getMessage()); 195 }

196 if (fontCache != null)

{ 197 fontCache.registerFailedFont(embedUrl, fileLastModified); 198 }

199 return null;
200 }
201 return fontInfoFromCustomFont(fontUrl, customFont, fontCache);
202 }
203 }
204

When thread1 and thread2 both enter IF at line 170, one can remove the font and then the other will get null at line 171.