Merge pull request #257 from jcarvalho/low-level-file-store

[io] Added low level API for file download

bennu-io/src/main/java/org/fenixedu/bennu/io/domain/FileStorage.java

@@ -4,9 +4,11 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Collections;
-import java.util.Optional;
 import java.util.Set;
 
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
 import com.google.common.io.Files;
 
 /**
@@ -86,30 +88,58 @@ public boolean isDefault() {
     }
 
     /**
-     * Returns the 'sendfile' path for the given file.
+     * Attempts to download the given file into the given response, in a more efficient manner than loading the file into memory
+     * and dumping it into the output stream.
      * 
-     * <strong>PRIVATE API:</strong>
-     * Note that this is Bennu IO private API, and should not be used outside this module.
-     * If you do use it, do it at your own risk, as this API is subject to change without
-     * any warning.
+     * This method returns a boolean indicating whether the low-level download was performed. If not, callers are expected to
+     * handle the file download in the regular manner.
      * 
      * @param file
-     *            The file to check
+     *            The file to download
+     * @param request
+     *            The HttpServletRequest that originated the file download request
+     * @param response
+     *            The HttpServletResponse to which the response should be written to
+     * @param start
+     *            The start offset within the file. The value of this number MUST be between 0 and the size of the file
+     * @param end
+     *            The end offset within the file. The value within this number MUST be between 1 and the size of the file
      * @return
-     *         An optional sendfile path
+     *         Whether a low-level download was performed
+     * @throws IOException
+     *             If an exception occurs while downloading the file
+     * @throws NullPointerException
+     *             If any of the arguments is null
      */
-    public static Optional<String> sendfilePath(GenericFile file) {
-        return file.getStorage().getSendfilePath(file.getContentKey());
+    public static boolean tryDownloadFile(GenericFile file, HttpServletRequest request, HttpServletResponse response, long start,
+            long end) throws IOException {
+        return file.getFileStorage().tryLowLevelDownload(file, request, response, start, end);
     }
 
-    /*
-     * Retrieves the file path for the given content key,
-     * if this storage supports it, and the file is indeed stored
-     * in the file system.
+    /**
+     * Attempts to perform a low-level download of the given file into the given response. {@link FileStorage} instances are
+     * expected to implement this whenever possible.
+     * 
+     * The default implementation returns {@code false}, as just tells any caller to fallback to downloading the file in the
+     * regular manner.
      * 
-     * By default returns an empty optional.
+     * @param file
+     *            The file to download
+     * @param request
+     *            The HttpServletRequest that originated the file download request
+     * @param response
+     *            The HttpServletResponse to which the response should be written to
+     * @param start
+     *            The start offset within the file. The value of this number MUST be between 0 and the size of the file
+     * @param end
+     *            The end offset within the file. The value within this number MUST be between 1 and the size of the file
+     * @return
+     *         Whether a low-level download was performed
+     * @throws IOException
+     *             If an exception occurs while downloading the file
      */
-    Optional<String> getSendfilePath(String contentKey) {
-        return Optional.empty();
+    protected boolean tryLowLevelDownload(GenericFile file, HttpServletRequest request, HttpServletResponse response, long start,
+            long end) throws IOException {
+        return false;
     }
 }

bennu-io/src/main/java/org/fenixedu/bennu/io/domain/LocalFileSystemStorage.java

@@ -15,6 +15,9 @@
 
 import jvstm.PerTxBox;
 
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -220,14 +223,63 @@ public InputStream readAsInputStream(String uniqueIdentification) {
         }
     }
 
+    /*
+     * Attempt to use the 'sendfile' primitive to download the file.
+     * 
+     * This feature may not be supported, or the file may not be stored in the
+     * filesystem, causing this not to work.
+     * 
+     * However, when it works, it provides great benefits, as the file must not
+     * be read to the Java Heap, only to be written to a socket, thus greatly
+     * reducing memory consumption.
+     */
+    @Override
+    protected boolean tryLowLevelDownload(GenericFile file, HttpServletRequest request, HttpServletResponse response, long start,
+            long end) {
+        if (supportsSendfile(request)) {
+            Optional<String> filePath = getSendfilePath(file.getContentKey());
+            if (filePath.isPresent()) {
+                handleSendfile(file, filePath.get(), request, response, start, end);
+                return true;
+            } else {
+                return false;
+            }
+        }
+        return false;
+    }
+
+    /*
+     * Sendfile is available, and the file is stored in the filesystem, so instruct
+     * the container to directly write the file.
+     * 
+     * For now, we only support the Tomcat-specific 'sendfile' implementation.
+     * See: http://tomcat.apache.org/tomcat-7.0-doc/aio.html#Asynchronous_writes
+     */
+    private static void handleSendfile(GenericFile file, String filename, HttpServletRequest request,
+            HttpServletResponse response, long start, long end) {
+        response.setHeader("X-Bennu-Sendfile", "true");
+        request.setAttribute("org.apache.tomcat.sendfile.filename", filename);
+        request.setAttribute("org.apache.tomcat.sendfile.start", Long.valueOf(start));
+        request.setAttribute("org.apache.tomcat.sendfile.end", Long.valueOf(end + 1));
+    }
+
+    /*
+     * Checks if the container supports usage of the 'sendfile' primitive.
+     * 
+     * For now, we only support the Tomcat-specific 'sendfile' implementation. 
+     * See: http://tomcat.apache.org/tomcat-7.0-doc/aio.html#Asynchronous_writes
+     */
+    private static boolean supportsSendfile(HttpServletRequest request) {
+        return Boolean.TRUE.equals(request.getAttribute("org.apache.tomcat.sendfile.support"));
+    }
+
     /*
      * Returns the absolute path for the given content key.
      * 
      * It must first check if the file indeed exists, in order
      * for the application to throw the proper exception.
      */
-    @Override
-    Optional<String> getSendfilePath(String uniqueIdentification) {
+    private Optional<String> getSendfilePath(String uniqueIdentification) {
         String path = getFullPath(uniqueIdentification) + uniqueIdentification;
         if (new File(path).exists()) {
             return Optional.of(path);

bennu-io/src/main/java/org/fenixedu/bennu/io/util/DownloadUtil.java

@@ -3,7 +3,6 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.util.Optional;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -126,7 +125,7 @@ public static void downloadFile(GenericFile file, HttpServletRequest request, Ht
             response.setStatus(HttpServletResponse.SC_OK);
         }
 
-        if (sendFile(file, request, response, start, end)) {
+        if (FileStorage.tryDownloadFile(file, request, response, start, end)) {
             return;
         }
         try (InputStream stream = file.getStream()) {
@@ -162,53 +161,4 @@ private static void copyStream(InputStream in, OutputStream out, long start, lon
         }
     }
 
-    /*
-     * Attempt to use the 'sendfile' primitive to download the file.
-     * 
-     * This feature may not be supported, or the file may not be stored in the
-     * filesystem, causing this not to work.
-     * 
-     * However, when it works, it provides great benefits, as the file must not
-     * be read to the Java Heap, only to be written to a socket, thus greatly
-     * reducing memory consumption.
-     */
-    private static boolean sendFile(GenericFile file, HttpServletRequest request, HttpServletResponse response, long start,
-            long end) {
-        if (supportsSendfile(request)) {
-            Optional<String> filePath = FileStorage.sendfilePath(file);
-            if (filePath.isPresent()) {
-                handleSendfile(file, filePath.get(), request, response, start, end);
-                return true;
-            } else {
-                return false;
-            }
-        }
-        return false;
-    }
-
-    /*
-     * Sendfile is available, and the file is stored in the filesystem, so instruct
-     * the container to directly write the file.
-     * 
-     * For now, we only support the Tomcat-specific 'sendfile' implementation.
-     * See: http://tomcat.apache.org/tomcat-7.0-doc/aio.html#Asynchronous_writes
-     */
-    private static void handleSendfile(GenericFile file, String filename, HttpServletRequest request,
-            HttpServletResponse response, long start, long end) {
-        response.setHeader("X-Bennu-Sendfile", "true");
-        request.setAttribute("org.apache.tomcat.sendfile.filename", filename);
-        request.setAttribute("org.apache.tomcat.sendfile.start", Long.valueOf(start));
-        request.setAttribute("org.apache.tomcat.sendfile.end", Long.valueOf(end + 1));
-    }
-
-    /*
-     * Checks if the container supports usage of the 'sendfile' primitive.
-     * 
-     * For now, we only support the Tomcat-specific 'sendfile' implementation.
-     * See: http://tomcat.apache.org/tomcat-7.0-doc/aio.html#Asynchronous_writes
-     */
-    private static boolean supportsSendfile(HttpServletRequest request) {
-        return Boolean.TRUE.equals(request.getAttribute("org.apache.tomcat.sendfile.support"));
-    }
-
 }