Improve PlexusIoZipFileResourceCollection performance by using JarFile

src/main/java/org/codehaus/plexus/archiver/zip/PlexusIoZipFileResourceCollection.java

@@ -18,11 +18,13 @@
 import java.io.Closeable;
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.nio.charset.Charset;
 import java.util.Enumeration;
 import java.util.Iterator;
+import java.util.jar.JarFile;
 import org.apache.commons.compress.archivers.zip.ZipArchiveEntry;
 import org.apache.commons.compress.archivers.zip.ZipFile;
 import org.codehaus.plexus.components.io.functions.SymlinkDestinationSupplier;
@@ -84,9 +86,10 @@ public URL getResource( String name )
         };
 
         final URL url = new URL( "jar:" + f.toURI().toURL() + "!/" );
+        final JarFile jarFile = new JarFile( f );
         final ZipFile zipFile = new ZipFile( f, charset != null ? charset.name() : "UTF8" );
         final Enumeration<ZipArchiveEntry> en = zipFile.getEntriesInPhysicalOrder();
-        return new ZipFileResourceIterator( en, url, zipFile, urlClassLoader );
+        return new ZipFileResourceIterator( en, url, jarFile, zipFile, urlClassLoader );
     }
 
     private static class ZipFileResourceIterator
@@ -96,14 +99,35 @@ private static class ZipFileResourceIterator
         private class ZipFileResource
             extends PlexusIoURLResource
         {
+            private final JarFile jarFile;
 
-            private ZipFileResource( ZipArchiveEntry entry )
+            private ZipFileResource( JarFile jarFile, ZipArchiveEntry entry )
             {
                 super( entry.getName(),
                        entry.getTime() == -1 ? PlexusIoResource.UNKNOWN_MODIFICATION_DATE : entry.getTime(),
                        entry.isDirectory() ? PlexusIoResource.UNKNOWN_RESOURCE_SIZE : entry.getSize(),
                        !entry.isDirectory(), entry.isDirectory(), true );
 
+                this.jarFile = jarFile;
+            }
+
+            @Override
+            public InputStream getContents() throws IOException {
+                // Uses the JarFile to get the input stream for the entry.
+                // The super method will do the same, why overriding it?
+                // But it will create new JarFile for every entry
+                // and that could be very expensive in some cases (when the JAR is signed).
+                // Enabling the URLConnection cache would solve the problem
+                // but the cache is global and shared during the build so
+                // if the AJR file changed during the causes another problem
+                // (see plexus-io#2).
+                // Using local JarFile instance solves the two issues -
+                // JarFile is initialized once so there is no performance penalty
+                // and it is local so if the file changed during the build
+                // would not be a problem.
+                // And we know the URL returned by getURL is part of the JAR
+                // because that is how we constructed it.
+                return jarFile.getInputStream( jarFile.getEntry( getName() ) );
             }
 
             @Override
@@ -131,9 +155,9 @@ private class ZipFileSymlinkResource
 
             private final ZipArchiveEntry entry;
 
-            private ZipFileSymlinkResource( ZipArchiveEntry entry )
+            private ZipFileSymlinkResource( JarFile jarFile, ZipArchiveEntry entry )
             {
-                super( entry );
+                super( jarFile, entry );
 
                 this.entry = entry;
             }
@@ -157,15 +181,18 @@ public boolean isSymbolicLink()
 
         private final URL url;
 
+        private final JarFile jarFile;
+
         private final ZipFile zipFile;
 
         private final URLClassLoader urlClassLoader;
 
-        public ZipFileResourceIterator( Enumeration<ZipArchiveEntry> en, URL url, ZipFile zipFile,
+        public ZipFileResourceIterator( Enumeration<ZipArchiveEntry> en, URL url, JarFile jarFile, ZipFile zipFile,
                                         URLClassLoader urlClassLoader )
         {
             this.en = en;
             this.url = url;
+            this.jarFile = jarFile;
             this.zipFile = zipFile;
             this.urlClassLoader = urlClassLoader;
         }
@@ -181,8 +208,8 @@ public PlexusIoResource next()
         {
             final ZipArchiveEntry entry = en.nextElement();
             return entry.isUnixSymlink()
-                       ? new ZipFileSymlinkResource( entry )
-                       : new ZipFileResource( entry );
+                       ? new ZipFileSymlinkResource( jarFile, entry )
+                       : new ZipFileResource( jarFile, entry );
 
         }
 
@@ -202,7 +229,14 @@ public void close()
             }
             finally
             {
-                zipFile.close();
+                try
+                {
+                    zipFile.close();
+                } finally
+                {
+                    jarFile.close();
+                }
+
             }
         }