Still improved caching: client must have header

Source/Core/src/ca/uqac/lif/jerrydog/CachedRequestCallback.java

@@ -21,6 +21,7 @@
 import java.util.HashSet;
 import java.util.Set;
 
+import com.sun.net.httpserver.Headers;
 import com.sun.net.httpserver.HttpExchange;
 
 /**
@@ -38,9 +39,17 @@ public class CachedRequestCallback extends RequestCallback
   protected Set<String> m_served;
 
   /**
-   * Whether caching is enabled
+   * Whether caching is enabled on the server side; this means that the
+   * server can answer a {@code 304} ("Not Modified") code to a client that
+   * requests a ressource it has already requested in the past.
    */
-  protected boolean m_cachingEnabled = true;
+  protected boolean m_serverCachingEnabled = true;
+
+  /**
+   * The time during which a client is allowed to keep the response of a
+   * request in its local cache before requesting it again.
+   */
+  protected int m_clientCachingInterval = 0;
 
   /**
    * The callback this object wraps around
@@ -65,24 +74,51 @@ public boolean fire(HttpExchange t)
   }
 
   /**
-   * Enables or disables the use of caching
+   * Enables or disables the use of caching  on the server side; this means that the
+   * server can answer a {@code 304} ("Not Modified") code to a client that
+   * requests a ressource it has already requested in the past.
    * @param b Set to {@code true} to enable caching, {@code false} otherwise
    */
   public void setCachingEnabled(boolean b)
   {
-    m_cachingEnabled = b;
+    m_serverCachingEnabled = b;
+  }
+
+  /**
+   * Sets the time during which a client is allowed to keep the response of a
+   * request in its local cache before requesting it again.
+   * @param interval The interval, in seconds
+   */
+  public void setCachingInterval(int interval)
+  {
+	  if (interval >= 0)
+	  {
+		  m_clientCachingInterval = interval;
+	  }
+	  else
+	  {
+		  m_clientCachingInterval = 0;
+	  }
   }
 
   @Override
   public CallbackResponse process(HttpExchange t)
   {
     URI u = t.getRequestURI();
     String path = u.getPath();
-    if (!m_cachingEnabled || !m_served.contains(path))
+    Headers h = t.getRequestHeaders();
+    if (!m_serverCachingEnabled || !m_served.contains(path) || !h.containsKey("If-Modified-Since"))
     {
       m_served.add(path);
-      return m_callback.process(t);
+      CallbackResponse response = m_callback.process(t);
+      if (m_clientCachingInterval > 0)
+      {
+    	  response.enableCaching(m_clientCachingInterval);
+      }
+      return response;
     }
+    // We get here only if 1. caching is enabled; 2. path has already been served;
+    // 3. browser says it has it in cache
     CallbackResponse out = new CallbackResponse(t, CallbackResponse.HTTP_NOT_MODIFIED, "", "");
     return out;
   }

Source/Core/src/ca/uqac/lif/jerrydog/CallbackResponse.java

@@ -115,6 +115,19 @@ public CallbackResponse disableCaching()
 		h.add("Expires", "0");
 		return this;
 	}
+
+	/**
+	 * Enables client-side caching in the HTTP response to be sent
+	 * @param duration The time, in seconds, that the browser can keep the
+	 * contents of the response in its cache
+	 * @return This response
+	 */
+	public CallbackResponse enableCaching(int duration)
+	{
+		Headers h = m_exchange.getResponseHeaders();
+		h.add("Cache-Control", "private, max-age=" + duration);
+		return this;
+	}
 
 	/**
 	 * Sets the HTTP response code

Source/Core/src/ca/uqac/lif/jerrydog/InnerFileServer.java

@@ -27,131 +27,154 @@
  */
 public class InnerFileServer extends Server
 {
-  protected String m_resourceFolder;
-
-  protected static final String s_resourceFolderDefaultName = "resource";
-
-  protected Class<? extends InnerFileServer> m_referenceClass;
-
-  public InnerFileServer(Class<? extends InnerFileServer> reference, boolean caching_enabled)
-  {
-    super();
-    m_resourceFolder = s_resourceFolderDefaultName;
-    InnerFileCallback ifc = new InnerFileCallback(m_resourceFolder, this.getClass());
-    if (caching_enabled)
-    {
-    	CachedRequestCallback crc = new CachedRequestCallback(ifc);
-    	registerCallback(0, crc);
-    }
-    else
-    {
-    	registerCallback(0, ifc);
-    }
-    m_referenceClass = this.getClass();    
-  }
-
-  protected InnerFileServer(Class<? extends InnerFileServer> c)
-  {
-    super();
-    m_resourceFolder = s_resourceFolderDefaultName;
-    registerCallback(0, new InnerFileCallback(m_resourceFolder, c));
-    m_referenceClass = c;
-  }
-
-  public InputStream getResourceAsStream(String path)
-  {
-    return m_referenceClass.getResourceAsStream(path);
-  }
-
-  public String getResourceFolderName()
-  {
-    return m_resourceFolder;
-  }
-
-  public static byte[] readBytes(InputStream is)
-  {
-    int nRead;
-    ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-    byte[] data = new byte[2048];
-    try
-    {
-      while ((nRead = is.read(data, 0, data.length)) != -1)
-      {
-        buffer.write(data, 0, nRead);
-      }
-      buffer.flush();
-    }
-    catch (IOException e)
-    {
-      e.printStackTrace();
-    }
-    return buffer.toByteArray();
-  }
-
-  static class PackageFileReader
-  {
-    public static String readPackageFile(Class<?> c, String path)
-    {
-      InputStream in = c.getResourceAsStream(path);
-      String out;
-      try
-      {
-        out = readPackageFile(in);
-      }
-      catch (IOException e)
-      {
-        e.printStackTrace();
-        return null;
-      }
-      return out;
-    }
-
-    public static byte[] readPackageFileToBytes(Class<?> c, String path)
-    {
-      InputStream in = getResourceAsStream(c, path);
-      byte[] file_contents = null;
-      if (in != null)
-      {
-        file_contents = InnerFileServer.readBytes(in);
-      }
-      return file_contents;
-    }
-
-    public static InputStream getResourceAsStream(Class<?> c, String path)
-    {
-      InputStream in = c.getResourceAsStream(path);
-      return in;
-    }
-
-    /**
-     * Reads a file and puts its contents in a string
-     * @param in The input stream to read
-     * @return The file's contents, and empty string if the file
-     * does not exist
-     */
-    public static String readPackageFile(InputStream in) throws IOException
-    {
-      if (in == null)
-      {
-        throw new IOException();
-      }
-      java.util.Scanner scanner = null;
-      StringBuilder out = new StringBuilder();
-      try
-      {
-        scanner = new java.util.Scanner(in, "UTF-8");
-        while (scanner.hasNextLine())
-        {
-          String line = scanner.nextLine();
-          out.append(line).append(System.getProperty("line.separator"));
-        }
-      }
-      finally
-      {
-        if (scanner != null)
-          scanner.close();
-      }
-      return out.toString();
-    }
-  }
+	/**
+	 * The name for the "resource" folder, where files will be fetched
+	 */
+	protected String m_resourceFolder;
+
+	/**
+	 * The default name for the "resource" folder, where files will be fetched
+	 */
+	protected static final String s_resourceFolderDefaultName = "resource";
+
+	/**
+	 * The class used as a reference for fetching files. All paths
+	 * will be relative to the location of this class in the project.
+	 */
+	protected Class<? extends InnerFileServer> m_referenceClass;
+
+	/**
+	 * Instantiates a new server with all caching disabled
+	 * @param reference The class used as a reference for fetching files. All
+	 * paths will be relative to the location of this class in the project.
+	 */
+	public InnerFileServer(Class<? extends InnerFileServer> reference)
+	{
+		this(reference, false, 0);
+	}
+
+	/**
+	 * Instantiates a new server
+	 * @param reference The class used as a reference for fetching files. All
+	 * paths will be relative to the location of this class in the project.
+	 * @param server_caching Sets whether the server caches past requests and
+	 * issues 304 codes for them
+	 * @param caching_interval The interval (in seconds) during which a client 
+	 * is allowed to locally cache the responses of past requests. Set to 0 
+	 * to disable client-side caching. 
+	 */
+	public InnerFileServer(Class<? extends InnerFileServer> reference, boolean server_caching, int caching_interval)
+	{
+		super();
+		m_resourceFolder = s_resourceFolderDefaultName;
+		InnerFileCallback ifc = new InnerFileCallback(m_resourceFolder, this.getClass());
+		if (server_caching)
+		{
+			CachedRequestCallback crc = new CachedRequestCallback(ifc);
+			crc.setCachingInterval(caching_interval);
+			registerCallback(0, crc);
+		}
+		else
+		{
+			registerCallback(0, ifc);
+		}
+		m_referenceClass = reference;    
+	}
+
+	public InputStream getResourceAsStream(String path)
+	{
+		return m_referenceClass.getResourceAsStream(path);
+	}
+
+	public String getResourceFolderName()
+	{
+		return m_resourceFolder;
+	}
+
+	public static byte[] readBytes(InputStream is)
+	{
+		int nRead;
+		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+		byte[] data = new byte[2048];
+		try
+		{
+			while ((nRead = is.read(data, 0, data.length)) != -1)
+			{
+				buffer.write(data, 0, nRead);
+			}
+			buffer.flush();
+		}
+		catch (IOException e)
+		{
+			e.printStackTrace();
+		}
+		return buffer.toByteArray();
+	}
+
+	static class PackageFileReader
+	{
+		public static String readPackageFile(Class<?> c, String path)
+		{
+			InputStream in = c.getResourceAsStream(path);
+			String out;
+			try
+			{
+				out = readPackageFile(in);
+			}
+			catch (IOException e)
+			{
+				e.printStackTrace();
+				return null;
+			}
+			return out;
+		}
+
+		public static byte[] readPackageFileToBytes(Class<?> c, String path)
+		{
+			InputStream in = getResourceAsStream(c, path);
+			byte[] file_contents = null;
+			if (in != null)
+			{
+				file_contents = InnerFileServer.readBytes(in);
+			}
+			return file_contents;
+		}
+
+		public static InputStream getResourceAsStream(Class<?> c, String path)
+		{
+			InputStream in = c.getResourceAsStream(path);
+			return in;
+		}
+
+		/**
+		 * Reads a file and puts its contents in a string
+		 * @param in The input stream to read
+		 * @return The file's contents, and empty string if the file
+		 * does not exist
+		 */
+		public static String readPackageFile(InputStream in) throws IOException
+		{
+			if (in == null)
+			{
+				throw new IOException();
+			}
+			java.util.Scanner scanner = null;
+			StringBuilder out = new StringBuilder();
+			try
+			{
+				scanner = new java.util.Scanner(in, "UTF-8");
+				while (scanner.hasNextLine())
+				{
+					String line = scanner.nextLine();
+					out.append(line).append(System.getProperty("line.separator"));
+				}
+			}
+			finally
+			{
+				if (scanner != null)
+					scanner.close();
+			}
+			return out.toString();
+		}
+	}
 }