Implemented SessionlessForm to workaround Wicket's stateful nature

diff --git a/src/com/gitblit/wicket/SessionlessForm.java b/src/com/gitblit/wicket/SessionlessForm.java
new file mode 100644 (file)
index 0000000..484e85e
--- /dev/null
+++ b/src/com/gitblit/wicket/SessionlessForm.java
@@ -0,0 +1,148 @@
+/*
+ * Copyright 2012 gitblit.com.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.gitblit.wicket;
+
+import java.text.MessageFormat;
+
+import org.apache.wicket.Component;
+import org.apache.wicket.PageParameters;
+import org.apache.wicket.markup.ComponentTag;
+import org.apache.wicket.markup.MarkupStream;
+import org.apache.wicket.markup.html.form.StatelessForm;
+import org.apache.wicket.protocol.http.WicketURLDecoder;
+import org.apache.wicket.protocol.http.request.WebRequestCodingStrategy;
+import org.apache.wicket.util.string.AppendingStringBuffer;
+import org.apache.wicket.util.string.Strings;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.gitblit.wicket.pages.BasePage;
+
+/**
+ * This class is used to create a stateless form that can POST or GET to a
+ * bookmarkable page regardless of the pagemap and even after session expiration
+ * or a server restart.
+ * 
+ * The trick is to embed "wicket:bookmarkablePage" as a hidden field of the form.
+ * Wicket already has logic to extract this parameter when it is trying
+ * to determine which page should receive the request.
+ * 
+ * The parameters of the containing page can optionally be included as hidden
+ * fields in this form.  Note that if a page parameter's name collides with any 
+ * child's wicket:id in this form then the page parameter is excluded.
+ * 
+ * @author James Moger
+ *
+ */
+public class SessionlessForm<T> extends StatelessForm<T> {
+       
+       private static final long serialVersionUID = 1L;
+
+       private static final String HIDDEN_DIV_START = "<div style=\"width:0px;height:0px;position:absolute;left:-100px;top:-100px;overflow:hidden\">";
+       
+       private final Class<? extends BasePage> pageClass;
+       
+       private final PageParameters pageParameters;
+       
+       private final Logger log = LoggerFactory.getLogger(SessionlessForm.class);
+
+       /**
+        * Sessionless forms must have a bookmarkable page class.  A bookmarkable
+        * page is defined as a page that has only a default and/or a PageParameter
+        * constructor.
+        * 
+        * @param id
+        * @param bookmarkablePageClass
+        */
+       public SessionlessForm(String id, Class<? extends BasePage> bookmarkablePageClass) {
+               this(id, bookmarkablePageClass, null);
+       }
+
+       /**
+        * Sessionless forms must have a bookmarkable page class.  A bookmarkable
+        * page is defined as a page that has only a default and/or a PageParameter
+        * constructor.
+        * 
+        * @param id
+        * @param bookmarkablePageClass
+        * @param pageParameters
+        */
+       public SessionlessForm(String id, Class<? extends BasePage> bookmarkablePageClass,
+                       PageParameters pageParameters) {
+               super(id);
+               this.pageClass = bookmarkablePageClass;
+               this.pageParameters = pageParameters;
+       }
+
+       
+       /**
+        * Append an additional hidden input tag that forces Wicket to correctly
+        * determine the destination page class even after a session expiration or
+        * a server restart.
+        * 
+        * @param markupStream
+        *            The markup stream
+        * @param openTag
+        *            The open tag for the body
+        */
+       @Override
+       protected void onComponentTagBody(final MarkupStream markupStream, final ComponentTag openTag)
+       {
+               // render the hidden bookmarkable page field
+               AppendingStringBuffer buffer = new AppendingStringBuffer(HIDDEN_DIV_START);
+               buffer.append("<input type=\"hidden\" name=\"")
+                       .append(WebRequestCodingStrategy.BOOKMARKABLE_PAGE_PARAMETER_NAME)
+                       .append("\" value=\":")
+                       .append(pageClass.getName())
+                       .append("\" />");
+
+               // insert the page parameters, if any, as hidden fields as long as they
+               // do not collide with any child wicket:id of the form.
+               if (pageParameters != null) {
+                       for (String key : pageParameters.keySet()) {
+                               Component c = get(key);
+                               if (c != null) {
+                                       // this form has a field id which matches the
+                                       // parameter name, skip embedding a hidden value
+                                       log.warn(MessageFormat.format("Skipping page parameter \"{0}\" from sessionless form hidden fields because it collides with a form child wicket:id", key));
+                                       continue;
+                               }
+                               String value = pageParameters.getString(key);
+                               buffer.append("<input type=\"hidden\" name=\"")
+                               .append(recode(key))
+                               .append("\" value=\"")
+                               .append(recode(value))
+                               .append("\" />");
+                       }
+               }
+
+               buffer.append("</div>");
+               getResponse().write(buffer);
+               super.onComponentTagBody(markupStream, openTag);
+       }
+       
+       /**
+        * Take URL-encoded query string value, unencode it and return HTML-escaped version
+        * 
+        * @param s
+        *            value to reencode
+        * @return reencoded value
+        */
+       private String recode(String s) {
+               String un = WicketURLDecoder.QUERY_INSTANCE.decode(s);
+               return Strings.escapeMarkup(un).toString();
+       }
+}