refactored common methods into a Util class

publicarray · publicarray · commit c4de2bd08608 · 2016-10-18T17:43:24.000+10:00
diff --git a/HttpRequest.java b/HttpRequest.java
@@ -2,6 +2,7 @@
 import java.net.*;
 import java.util.*;
 import java.text.SimpleDateFormat;
+import static SSHelpers.Util.*;
 
 public class HttpRequest {
     /** Help variables */
@@ -102,9 +103,7 @@ public HttpResponse askServerIfvalid(Date lastModified, String etag) {
             headers += "If-None-Match: " + etag + CRLF;
         } if (lastModified != null) {
             // If-Modified-Since: Thu, 13 Oct 2016 00:36:43 GMT\r\n
-            SimpleDateFormat dateFormat = new SimpleDateFormat ("E, dd MMM yyyy HH:mm:ss z");
-            dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
-            headers += "If-Modified-Since: " + dateFormat.format(lastModified) + CRLF;
+            headers += "If-Modified-Since: " + dateToString(lastModified) + CRLF;
         }
 
         headers += "Host: " + host + CRLF;
diff --git a/HttpResponse.java b/HttpResponse.java
@@ -1,9 +1,7 @@
 import java.io.*;
 import java.net.*;
 import java.util.*;
-import java.text.SimpleDateFormat;
-import java.text.ParseException;
-
+import static SSHelpers.Util.*;
 
 public class HttpResponse {
     final static String CRLF = "\r\n";
@@ -228,22 +226,6 @@ public Socket send(Socket host) {
         return host;
     }
 
-    private Date toDate(String dateStr, String format) {
-        try {
-            SimpleDateFormat inFormat = new SimpleDateFormat(format);
-            inFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
-            return inFormat.parse(dateStr);
-        } catch (ParseException e) {
-            System.out.println("Parse date error: " + e + " -- at position:" + e.getErrorOffset());
-        }
-        return null;
-    }
-
-    private Date toDate(String dateStr) {
-        String format = "E, dd MMM yyyy HH:mm:ss z"; // Mon, 13 Jun 2016 21:06:31 GMT
-        return toDate(dateStr, format);
-    }
-
     // check if response is still valid using the (now old) expires header
     public boolean isExpired() {
         if (lastModified != null && expires != null) {
diff --git a/Makefile b/Makefile
@@ -16,7 +16,8 @@ clean:
 docs: *.java
 	$(JDOC) $^ -d docs \
 		-windowtitle $(DOCTITLE) \
-		-doctitle $(DOCTITLE)
+		-doctitle $(DOCTITLE) \
+		-subpackages SSHelpers
 
 docs-clean:
 	$(RM) docs/*
diff --git a/SCache.java b/SCache.java
@@ -3,13 +3,20 @@
 import java.util.*;
 import java.util.HashMap;
 import java.text.SimpleDateFormat;
+import static SSHelpers.Util.*;
 
 public class SCache {
+    // private Helpers helpers = new Helpers();
+
+    // A key value store in memory
     private Map<String, HttpResponse> cacheStore;
+    // A HttpRequest used to send If-None-Match and If-Modified-Since requests to the server
     HttpRequest request;
 
     /**
-     * [SCache description]
+     * This SCache class contains the cache for the proxy.
+     * It provides methods to add, validate and get items from the cache.
+     * The cache uses the URL as a key to lookup items in the cache
      */
     public SCache() {
         // synchronised HasMap prevents data corruption when reading while writing the Map
@@ -18,7 +25,7 @@ public SCache() {
     }
 
     /**
-     * Add the HttpResponse into the HashMap cache with the url as the key.
+     * Adds the HttpResponse into the cache with the url as the key.
      * @param  key   The Url
      * @param  value The HttpResponse
      * @return       The given value HttpResponse
@@ -29,7 +36,8 @@ public HttpResponse put(String key, HttpResponse value) {
     }
 
     /**
-     * Retrieves the HttpResponse from HashMap cache by looking up the url
+     * Retrieves the HttpResponse from cache by looking up the url.
+     * The HttpResponse is checked to make sure it is fresh.
      * @param  key The Url
      * @return     The Cached HttpResponse
      */
@@ -50,9 +58,12 @@ public HttpResponse get(String key) {
         return value;
     }
 
-    // check if response is still valid
     /**
-     * Determine if the Cache HttpResonse is still fresh.
+     * Determines if the cached HttpResonse is still fresh and updates the cache when it is not.
+     * It checks that the response has not expired by checking the Last-Modified and the Expired header
+     * in the response. If no expired header is present the server is asked with If-None-Match and the
+     * If-Modified-Since headers. If the server response status code is not a 304 Not Modified response
+     * than the new response updates the value in the cache.
      * @param  requestURL The key in the cache
      * @param  response   The value in the cache
      * @return            isValid? as in is the item in the cache fresh?
@@ -63,7 +74,6 @@ public boolean isValid(String requestURL, HttpResponse response) {
             return true;
         }
 
-        // HttpRequest check = new HttpRequest(request); // deep copy
         request.setHost(getHost(requestURL));
         request.setPort(getPort(requestURL));
         request.URL = getLocation(requestURL);
@@ -72,7 +82,6 @@ public boolean isValid(String requestURL, HttpResponse response) {
         if (newResponse == null) { // if error
             return true; // use the cached response if new response has an unrecoverable error.
         }
-        // HttpResponse r = new HttpRequest(request, response.lastModified, response.etag).send(); // ask server
         if (newResponse.status == 304) { // Not modified, so still valid
             System.out.println("SCACHE: 304 Not modified");
             return true;
@@ -81,89 +90,5 @@ public boolean isValid(String requestURL, HttpResponse response) {
             put(requestURL, newResponse); // save the new response
             return false;
         }
-
-        // return false;
-    }
-
-    /**
-     * From a url string get the hostname
-     * @param  url The Url (http://example.com/foo)
-     * @return     The Hostname (example.com)
-     */
-    public static String getHost(String url) {
-        if (url == null || url.length() <= 0) {
-            return "";
-        }
-
-        int start = url.indexOf("//");
-        if (start == -1) {
-            return "";
-        }
-        start += 2;
-
-        int end = url.indexOf('/', start);
-        if (end == -1) {
-            return "";
-        }
-
-        return url.substring(start, end);
-    }
-
-    /**
-     * From a utl string get the port number
-     * @param  url The Url (http://example.com:50/foo)
-     * @return     The Port number (50)
-     */
-    public static int getPort(String url) {
-        if (url == null || url.length() <= 0) {
-            return 80;
-        }
-
-        int start = url.indexOf("//");
-        if (start == -1) {
-            return 80;
-        }
-
-        start += 2;
-
-        int end = url.indexOf('/', start);
-        if (end == -1) {
-            return 80;
-        }
-
-        int port = url.indexOf(':', start);
-        if (port == -1) {
-            return 80;
-        }
-
-        if (port < end) {
-            end = port;
-        }
-
-        return Integer.parseInt(url.substring(port, end));
-    }
-
-    /**
-     * From a url string get the location
-     * @param  url The Url (http://example.com/foo)
-     * @return     The location (/foo)
-     */
-    public static String getLocation(String url) {
-        if (url == null || url.length() <= 0) {
-            return "";
-        }
-
-        int start = url.indexOf("//");
-        if (start == -1) {
-            return "";
-        }
-        start += 2;
-
-        int end = url.indexOf('/', start);
-        if (end == -1) {
-            return "";
-        }
-
-        return url.substring(end);
     }
 }
diff --git a/SSHelpers/Util.java b/SSHelpers/Util.java
@@ -0,0 +1,116 @@
+package SSHelpers;
+
+import java.util.Date;
+import java.util.TimeZone;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+
+public class Util {
+    /**
+     * From a url string get the host-name
+     * @param  url The Url E.g. http://example.com/foo
+     * @return     The Hostname E.g. example.com
+     */
+    public static String getHost(String url) {
+        if (url == null || url.length() <= 0) {
+            return "";
+        }
+
+        int start = url.indexOf("//");
+        if (start == -1) {
+            return "";
+        }
+        start += 2;
+
+        int end = url.indexOf('/', start);
+        if (end == -1) {
+            return "";
+        }
+
+        return url.substring(start, end);
+    }
+
+    /**
+     * From a url string get the port number
+     * @param  url The Url E.g. http://example.com:50/foo
+     * @return     The Port number E.g. 50
+     */
+    public static int getPort(String url) {
+        if (url == null || url.length() <= 0) {
+            return 80;
+        }
+
+        int start = url.indexOf("//");
+        if (start == -1) {
+            return 80;
+        }
+
+        start += 2;
+
+        int end = url.indexOf('/', start);
+        if (end == -1) {
+            return 80;
+        }
+
+        int port = url.indexOf(':', start);
+        if (port == -1) {
+            return 80;
+        }
+
+        if (port < end) {
+            end = port;
+        }
+
+        return Integer.parseInt(url.substring(port, end));
+    }
+
+    /**
+     * From a url string get the location
+     * @param  url The Url  E.g. http://example.com/foo
+     * @return     The location E.g. /foo
+     */
+    public static String getLocation(String url) {
+        if (url == null || url.length() <= 0) {
+            return "";
+        }
+
+        int start = url.indexOf("//");
+        if (start == -1) {
+            return "";
+        }
+        start += 2;
+
+        int end = url.indexOf('/', start);
+        if (end == -1) {
+            return "";
+        }
+
+        return url.substring(end);
+    }
+
+    public static Date toDate(String dateStr, String format) {
+        try {
+            SimpleDateFormat inFormat = new SimpleDateFormat(format);
+            inFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
+            return inFormat.parse(dateStr);
+        } catch (ParseException e) {
+            System.out.println("Parse date error: " + e + " -- at position:" + e.getErrorOffset());
+        }
+        return null;
+    }
+
+    public static Date toDate(String dateStr) {
+        String format = "E, dd MMM yyyy HH:mm:ss z"; // Mon, 13 Jun 2016 21:06:31 GMT
+        return Util.toDate(dateStr, format);
+    }
+
+    public static String dateToString(Date date, String format) {
+        SimpleDateFormat dateFormat = new SimpleDateFormat (format);
+        dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
+        return dateFormat.format(date);
+    }
+
+    public static String dateToString(Date date) {
+        return Util.dateToString(date, "E, dd MMM yyyy HH:mm:ss z");
+    }
+}
