Delete Cached file in case of error

[stoecker]

The URL ​https://maps.nlsc.gov.tw/OpenData/wmts? doesn't work. JOSM can't find any layer, but on first view the XML looks good to me.

Reason: The server delivered (for a short time?) a XML without Layers. This was cached and used again and again.

A cached file should be deleted when an error occurs.

[GerdP]

A cached file should be deleted when an error occurs.

Any idea how to achive that?
My understanding is that any code where CachedFile is used hast to be checked and changed to make sure that any kind of malformed data causes a delete from the cache.

[taylor.smock]

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[taylor.smock]

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[taylor.smock]

Any idea how to achive that?

Probably a try-catch block if an exception is thrown. Problem being, I don't think there was an exception thrown here.

We could try reloading entries (on some kind of backoff function to avoid overloading the server) if the following is true:

1. A parsing exception is thrown
2. A source that is supposed to have layers does not have layers
3. Other validation checks on the source fail

[taylor.smock]

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[taylor.smock]

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[taylor.smock]

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[stoecker]

Milestone closed.

[taylor.smock]

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[taylor.smock]

We could try doing something like this:

src/org/openstreetmap/josm/io/CachedFile.java

@@ -20 +20 @@
 import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 import java.util.zip.ZipEntry;
@@ -335 +337 @@
         return ze.b;
     }
 
+    /**
+     * Perform parsing of the local file. In the event that a specified set of exceptions occur, we clear the file
+     * and rethrow the exception.
+     * @param runnable The callable that may throw an exception
+     * @param improperLocalFile The list of exceptions that indicate that we need to redownload the file
+     * @param <T> The callable return type
+     * @throws Exception
+     */
+    public <T> T performParsing(Callable<T> runnable, Collection<Class<? extends Throwable>> improperLocalFile) throws Exception {
+        try {
+            return runnable.call();
+        } catch (Exception throwable) {
+            if (improperLocalFile.contains(throwable.getClass())) {
+                this.clear();
+            }
+            throw throwable;
+        }
+    }
+
     private Pair<String, InputStream> findZipEntryImpl(String extension, String namepart) {
         File file = null;
         try {

I'm not certain if I want to do that in CachedFile or if we want to try and do that in catch blocks for all the places where we use CachedFile.

[taylor.smock]

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[taylor.smock]

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[taylor.smock]

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