[feature] Adds in memory cache for query results

- Use in memory caching for resuls smaller 4 MB adding new
  CachedContentFile and companion test case
- Extended XmlRpcTest to improve coverage of RpcConnection
- Added new QueryResultCacheTest

Signed-off-by: Patrick Reinhart <patrick@reini.net>

exist-core/src/main/java/org/exist/util/io/MemoryContentsInputStream.java

@@ -26,7 +26,6 @@
 
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.OutputStream;
 import java.util.concurrent.atomic.AtomicLongFieldUpdater;
 
 /**
@@ -84,7 +83,7 @@ public int read() throws IOException {
     public int read(byte[] b, int off, int len) throws IOException {
         boolean success = false;
         int read = 0;
-        while (!success) {
+        while (!success && len > 0) {
             long positionBefore = POSITION_UPDATER.get(this);
             read = this.memoryContents.read(b, positionBefore, off, len);
             if (read < 1) {
@@ -115,13 +114,4 @@ public long skip(long n) throws IOException {
         }
         return skipped;
     }
-
-    // Java 9 method, has to compile under Java 1.7 so no @Override
-    public long transferTo(OutputStream out) throws IOException {
-        long positionBefore = POSITION_UPDATER.get(this);
-        long written = this.memoryContents.transferTo(out, positionBefore);
-        POSITION_UPDATER.set(this, this.memoryContents.size());
-        return written;
-    }
-
 }

exist-core/src/main/java/org/exist/util/io/VirtualTempPath.java

@@ -52,6 +52,10 @@ public final class VirtualTempPath implements ContentFile {
     @GuardedBy("lock")
     private Path contentFile;
 
+    public VirtualTempPath(TemporaryFileManager tempFileManager) {
+        this(DEFAULT_IN_MEMORY_SIZE, tempFileManager);
+    }
+
     public VirtualTempPath(int inMemorySize, TemporaryFileManager tempFileManager) {
         this.inMemorySize = inMemorySize;
         this.lock = new StampedLock();
@@ -96,6 +100,7 @@ public OutputStream newOutputStream() throws IOException {
         }
     }
 
+    @Override
     public InputStream newInputStream() throws IOException {
         long stamp = lock.readLock();
         try {
@@ -105,7 +110,7 @@ public InputStream newInputStream() throws IOException {
             if (content != null) {
                 return new MemoryContentsInputStream(content);
             }
-            return new ByteArrayInputStream(EMPTY_BUFFER);
+            return InputStream.nullInputStream();
         } finally {
             lock.unlockRead(stamp);
         }
@@ -128,6 +133,7 @@ public void close() {
         }
     }
 
+    @Override
     public long size() {
         long stamp = lock.readLock();
         try {
@@ -140,6 +146,7 @@ public long size() {
         }
     }
 
+    @Override
     public byte[] getBytes() {
         long stamp = lock.readLock();
         try {

exist-core/src/main/java/org/exist/xmlrpc/CachedContentFile.java

@@ -0,0 +1,48 @@
+/*
+ * eXist-db Open Source Native XML Database
+ * Copyright (C) 2001 The eXist-db Authors
+ *
+ * info@exist-db.org
+ * http://www.exist-db.org
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+package org.exist.xmlrpc;
+
+import org.exist.util.io.ContentFile;
+
+/**
+ * @author <a href="mailto:patrick@reini.net">Patrick Reinhart</a>
+ */
+public final class CachedContentFile extends AbstractCachedResult {
+    private final ContentFile result;
+
+    public CachedContentFile(final ContentFile result) {
+        super(0);
+        this.result = result;
+    }
+
+    @Override
+    public ContentFile getResult() {
+        return result;
+    }
+
+    @Override
+    protected void doClose() {
+        if (result != null) {
+            result.close();
+        }
+    }
+}

exist-core/src/main/java/org/exist/xmlrpc/QueryResultCache.java

@@ -73,12 +73,17 @@ public AbstractCachedResult get(final int cacheId) {
 
     public QueryResult getResult(final int cacheId) {
         final AbstractCachedResult acr = get(cacheId);
-        return (acr != null && acr instanceof QueryResult) ? (QueryResult) acr : null;
+        return (acr != null && acr instanceof QueryResult result) ? result : null;
     }
 
     public SerializedResult getSerializedResult(final int cacheId) {
         final AbstractCachedResult acr = get(cacheId);
-        return (acr != null && acr instanceof SerializedResult) ? (SerializedResult) acr : null;
+        return (acr != null && acr instanceof SerializedResult result) ? result : null;
+    }
+
+    public CachedContentFile getCachedContentFile(final int cacheId) {
+        final AbstractCachedResult acr = get(cacheId);
+        return (acr != null && acr instanceof CachedContentFile result) ? result : null;
     }
 
     public void remove(final int cacheId) {

exist-core/src/main/java/org/exist/xmlrpc/RpcAPI.java

@@ -31,7 +31,6 @@
 import org.exist.security.PermissionDeniedException;
 import org.exist.security.internal.aider.ACEAider;
 import org.exist.util.LockException;
-import org.exist.xmldb.XmldbURI;
 import org.exist.xquery.XPathException;
 import org.xml.sax.SAXException;
 
@@ -112,7 +111,7 @@ public interface RpcAPI {
     /**
      * Retrieve document by name. XML content is indented if prettyPrint is set
      * to >=0. Use supplied encoding for output.
-     *
+     * <p>
      * This method is provided to retrieve a document with encodings other than
      * UTF-8. Since the data is handled as binary data, character encodings are
      * preserved. byte[]-values are automatically BASE64-encoded by the XMLRPC
@@ -132,7 +131,7 @@ byte[] getDocument(String name, String encoding, int prettyPrint)
      * Retrieve document by name. XML content is indented if prettyPrint is set
      * to &gt;=0. Use supplied encoding for output and apply the specified
      * stylesheet.
-     *
+     * <p>
      * This method is provided to retrieve a document with encodings other than
      * UTF-8. Since the data is handled as binary data, character encodings are
      * preserved. byte[]-values are automatically BASE64-encoded by the XMLRPC
@@ -152,7 +151,7 @@ byte[] getDocument(String name, String encoding, int prettyPrint, String stylesh
     /**
      * Retrieve document by name. All optional output parameters are passed as
      * key/value pairs int the <code>parameters</code>.
-     *
+     * <p>
      * Valid keys may either be taken from
      * {@link javax.xml.transform.OutputKeys} or
      * {@link org.exist.storage.serializers.EXistOutputKeys}. For example, the
@@ -247,10 +246,10 @@ List<String> getCollectionListing(final String collection)
     List<String> getDocumentListing(String collection)
             throws EXistException, PermissionDeniedException, URISyntaxException;
 
-    Map<String, List> listDocumentPermissions(String name)
+    Map<String, List<Object>> listDocumentPermissions(String name)
             throws EXistException, PermissionDeniedException, URISyntaxException;
 
-    Map<XmldbURI, List> listCollectionPermissions(String name)
+    Map<String, List<Object>> listCollectionPermissions(String name)
             throws EXistException, PermissionDeniedException, URISyntaxException;
 
     /**
@@ -497,6 +496,7 @@ byte[] query(
      * @throws PermissionDeniedException If the current user is not allowed to perform this action
      * @deprecated use List query() or int executeQuery() instead
      */
+    @Deprecated
     Map<String, Object> querySummary(String xquery)
             throws EXistException, PermissionDeniedException;
 
@@ -612,7 +612,7 @@ String uploadCompressed(String file, byte[] data, int length)
 
     /**
      * Parse a file previously uploaded with upload.
-     *
+     * <p>
      * The temporary file will be removed.
      *
      * @param localFile temporary file name
@@ -749,6 +749,7 @@ Map<String, Object> execute(String path, Map<String, Object> parameters)
      *
      * @deprecated Use {@link #executeT(String, Map)} instead.
      */
+    @Deprecated
     Map<String, Object> executeT(String path, Map<String, Object> parameters)
             throws EXistException, PermissionDeniedException;
 
@@ -926,7 +927,7 @@ String hasUserLock(String path)
 
     List<String> getGroups() throws EXistException, PermissionDeniedException;
 
-    List<List> getIndexedElements(String collectionName, boolean inclusive)
+    List<List<Object>> getIndexedElements(String collectionName, boolean inclusive)
             throws EXistException, PermissionDeniedException, URISyntaxException;
 
     boolean releaseQueryResult(int handle);