Fix and simplify handling of JSPParser classloader

The classloader was reset after each invocation by calls to
resetClassLoaders, so there is already little caching present here.

The old behavior though posed a different problem: the classloaders
were shared into multiple threads and calls to resetClassLoaders were
not coordinated, so the "slower" thread could be faced with a closed
classloader. For an URLClassLoader this means, that classes already
loaded work, new classes can't be loaded. This leads to difficult to
debug situations.

At runtime this was observed as:

Unable to read TLD "META-INF/liferay-portlet-ext.tld" from JAR file
"file:/home/matthias/.m2/repository/com/liferay/portal/release.portal.api/7.4.3.94-ga94/release.portal.api-7.4.3.94-ga94.jar":
org.apache.jasper.JasperException: PWC6112: Failed to load or
instantiate TagExtraInfo class: com.liferay.taglib.portlet.ActionURLTei

enterprise/web.jspparser/extsrc/org/netbeans/modules/web/jspparser_ext/WebAppParseSupport.java

@@ -129,12 +129,7 @@ public class WebAppParseSupport implements WebAppParseProxy, PropertyChangeListe
     private ServletContext editorContext;
     private ServletContext diskContext;
     private JspRuntimeContext rctxt;
-    private ParserClassLoader waClassLoader;
-    private ParserClassLoader waContextClassLoader;
-
-    // This is intended for tests exclusively!!!
-    @SuppressWarnings("FieldMayBeFinal")
-    private static boolean noReset = false;
+    private URL[][] classLoaderSources = null;
 
     // @GuardedBy(this)
     /**
@@ -226,8 +221,6 @@ public JspParserAPI.JspOpenInfo getJspOpenInfo(FileObject jspFile, boolean useEd
             return new JspParserAPI.JspOpenInfo(epd.isXMLSyntax(), epd.getEncoding());
         } catch (IOException | JasperException | RuntimeException e) {
             LOG.fine(e.getMessage());
-        } finally {
-            resetClassLoaders();
         }
         return DEFAULT_JSP_OPEN_INFO;
     }
@@ -313,34 +306,14 @@ private void createClassLoaders() {
         }
 
         @SuppressWarnings("CollectionsToArray")
-        URL[] loadingURLs = loadingTable.values().toArray(new URL[0]);
-        @SuppressWarnings("CollectionsToArray")
-        URL[] tomcatURLs = tomcatTable.values().toArray(new URL[0]);
+        URL[][] urls = {
+            loadingTable.values().toArray(new URL[0]),
+            tomcatTable.values().toArray(new URL[0])
+        };
 
-        waClassLoader = new ParserClassLoader(loadingURLs, tomcatURLs, getClass().getClassLoader());
-        waContextClassLoader = new ParserClassLoader(loadingURLs, tomcatURLs, getClass().getClassLoader());
+        this.classLoaderSources = urls;
     }
 
-    // #128360
-    private void resetClassLoaders() {
-        if (noReset) {
-            return;
-        }
-        URL[] loadingURLs = waClassLoader.getLoadingURLs();
-        URL[] tomcatURLs = waClassLoader.getTomcatURLs();
-        URL[] loadingContextURLs = waContextClassLoader.getLoadingURLs();
-        URL[] tomcatContextURLs = waContextClassLoader.getTomcatURLs();
-
-        try {
-            waClassLoader.close();
-            waContextClassLoader.close();
-        } catch (IOException | RuntimeException e) {
-            LOG.log(Level.WARNING, null, e);
-        }
-        waClassLoader = new ParserClassLoader(loadingURLs, tomcatURLs, waClassLoader.getParent());
-        waContextClassLoader = new ParserClassLoader(loadingContextURLs, tomcatContextURLs, waContextClassLoader.getParent());
-     }
-
     // #127379 - XXX review after listening on a web module is possible
     private FileObject getWebInf() {
         if (wmRoot == null) {
@@ -444,10 +417,10 @@ public JspParserAPI.ParseResult analyzePage(FileObject jspFile, /*String compila
         checkReinitCachesTask();
         JspCompilationContext ctxt = createCompilationContext(jspFile, true);
 
-        try {
-            return callTomcatParser(jspFile, ctxt, waContextClassLoader, errorReportingMode);
-        } finally {
-            resetClassLoaders();
+        try (URLClassLoader cl = new ParserClassLoader(this.classLoaderSources[0], this.classLoaderSources[1], getClass().getClassLoader())) {
+            return callTomcatParser(jspFile, ctxt, cl, errorReportingMode);
+        } catch (IOException ex) {
+            throw new RuntimeException(ex);
         }
     }
 
@@ -484,7 +457,8 @@ public synchronized URLClassLoader getWAClassLoader() {
             reinitOptions();
         }
         // XXX #128360 - classloader is leaking out - no chance to close it
-        return waClassLoader;
+        // Callers must close the classloader as soon as possible!
+        return new ParserClassLoader(this.classLoaderSources[0], this.classLoaderSources[1], getClass().getClassLoader());
     }
 
     @Override
@@ -717,22 +691,24 @@ void reinitTagLibMappings() {
             }
 
             Thread compThread = new WebAppParseSupport.InitTldLocationCacheThread(lc);
-            compThread.setContextClassLoader(waContextClassLoader);
-            long start = 0;
-            if (LOG.isLoggable(Level.FINE)) {
-                start = System.currentTimeMillis();
-                LOG.fine("InitTldLocationCacheThread start"); //NOI18N
-            }
-            compThread.start();
-
-            try {
-                compThread.join();
+            try (URLClassLoader cl = new ParserClassLoader(this.classLoaderSources[0], this.classLoaderSources[1], getClass().getClassLoader())) {
+                compThread.setContextClassLoader(cl);
+                long start = 0;
                 if (LOG.isLoggable(Level.FINE)) {
-                    long end = System.currentTimeMillis();
-                    LOG.log(Level.FINE, "InitTldLocationCacheThread finished in {0} ms", (end - start)); //NOI18N
+                    start = System.currentTimeMillis();
+                    LOG.fine("InitTldLocationCacheThread start"); //NOI18N
+                }
+                compThread.start();
+
+                try {
+                    compThread.join();
+                    if (LOG.isLoggable(Level.FINE)) {
+                        long end = System.currentTimeMillis();
+                        LOG.log(Level.FINE, "InitTldLocationCacheThread finished in {0} ms", (end - start)); //NOI18N
+                    }
+                } catch (InterruptedException e) {
+                    LOG.log(Level.INFO, null, e);
                 }
-            } catch (InterruptedException e) {
-                LOG.log(Level.INFO, null, e);
             }
 
             // obtain the current mappings after parsing
@@ -754,7 +730,7 @@ void reinitTagLibMappings() {
             }
             // cache tld files under WEB-INF directory as well
             mappings.putAll(getImplicitLocation());
-        } catch (NoSuchFieldException | IllegalAccessException e) {
+        } catch (NoSuchFieldException | IllegalAccessException | IOException e) {
             LOG.log(Level.INFO, null, e);
         }
     }