[Openjnlp-devel] OpenJNLP patches for extraneous retrieval of launch URLs

[Nathan M. <nm...@vi...>]

Hello again,

Following up on our recent conversations, here are some OpenJNLP patches
to address the extraneous repeated retrieval of launch URLs.

- JNLPParser.URLJNLPParser.openInputStream(): Return the InputStream
  from the connection recently opened, rather than launching a new
  connection.

- JNLPParser.CachedJNLPParser.openInputStream(): avoid updating a resource
  that was just fetched.

- CachedResource.update(): Do not query the resource for last modified
  time; instead, GET it with an If-Modified-Since request header.

This addresses most of the extraneous GETs and HEADs of the launch URL.
There is still one case that will require a bit more intricacy to address:
OpenJNLP depends on finding an existing cache entry, even though it
will not be used because it is out of date.  If no such entry exists,
it will be fetched, stored in the cache, and subsequently not used. This
behavior cannot be stopped by supplying a <jnlp> element without an
"href" attribute.

I cannot guarantee that these changes do not violate some important
assumptions about some cached or remote resources - but I don't think
they do.

Nathan Meyers
nm...@vi...


Index: src/org/nanode/jnlp/JNLPParser.java
===================================================================
diff -u -r1.1.1.1 JNLPParser.java
--- src/org/nanode/jnlp/JNLPParser.java	18 Nov 2002 12:04:18 -0000	1.1.1.1
+++ src/org/nanode/jnlp/JNLPParser.java	26 Nov 2002 18:18:06 -0000
@@ -490,7 +490,7 @@
                 throw new IOException("Bad MIME type: " + uc.getContentType());
             }
 
-            return srcURL.openStream();
+            return uc.getInputStream();
         }
     }
 
@@ -537,11 +537,15 @@
 
             try {
                 // if descriptor not cached yet, add it to cache
-                if (!cacheEntry.isResourceCached(ref) && !cacheEntry.addResource(ref)) {
-                    throw new IOException("failed to add descriptor to cache for " + cacheEntry.getTitle());
+                boolean doUpdate = true;
+                if (!cacheEntry.isResourceCached(ref)) {
+                    doUpdate = false;
+                    if (!cacheEntry.addResource(ref))
+                        throw new IOException("failed to add descriptor to cache for " + cacheEntry.getTitle());
                 }
 
-                if ((res = cacheEntry.getResource(ref, true)) == null) {
+                // Get the resource, updating it if we didn't just fetch it
+                if ((res = cacheEntry.getResource(ref, doUpdate)) == null) {
                     throw new IOException("descriptor not in cache");
                 }
             } catch (Exception e) {
Index: src/org/nanode/launcher/cache/CachedResource.java
===================================================================
diff -u -r1.1.1.1 CachedResource.java
--- src/org/nanode/launcher/cache/CachedResource.java	18 Nov 2002 12:04:18 -0000	1.1.1.1
+++ src/org/nanode/launcher/cache/CachedResource.java	26 Nov 2002 18:18:06 -0000
@@ -138,12 +138,6 @@
     }
 
     public boolean update() {
-        long remoteLastModified = getRemoteLastModified();
-
-        if (remoteLastModified == 0L || remoteLastModified <= lastModified) {
-            return false;
-        }
-
         // do a cache update
         synchronized (reference) {
             statistics.reset();
@@ -153,6 +147,11 @@
 
             try {
                 URLConnection uc = reference.getURL().openConnection();
+                uc.setIfModifiedSince(lastModified);
+                if (uc instanceof HttpURLConnection
+                    && ((HttpURLConnection) uc).getResponseCode()
+                      == HttpURLConnection.HTTP_NOT_MODIFIED)
+                    return false;
 
                 lastModified = uc.getLastModified();
                 statistics.contentLength = uc.getContentLength();
@@ -182,7 +181,6 @@
                     }
                 }
 
-                lastModified = remoteLastModified;
             } catch (Exception e) {
                 System.err.println(e);
                 statistics.aborted = true;