First cut of the AJAX framework

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@3327 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/web/app/servlet/ajax/AjaxCommand.java

@@ -0,0 +1,37 @@
+package org.alfresco.web.app.servlet.ajax;
+
+import java.io.IOException;
+
+import javax.faces.context.FacesContext;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * Interface for all Ajax commands executed by this servlet.
+ * 
+ * The method is responsible for invoking the underlying managed bean 
+ * and dealing with the response.
+ * 
+ * @author gavinc
+ */
+public interface AjaxCommand
+{
+   /**
+    * Invokes the relevant method on the bean represented by the given
+    * expression. Parameters required to call the method can be retrieved
+    * from the request. 
+    * 
+    * Currently the content type of the response will always be text/html, in the 
+    * future sublcasses may provide a mechanism to allow the content type to be set
+    * dynamically.
+    * 
+    * @param facesContext FacesContext
+    * @param expression The binding expression
+    * @param request The request
+    * @param response The response
+    */
+   public abstract void execute(FacesContext facesContext, String expression,
+         HttpServletRequest request, HttpServletResponse response) 
+         throws ServletException, IOException;
+}

source/java/org/alfresco/web/app/servlet/ajax/AjaxServlet.java

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+package org.alfresco.web.app.servlet.ajax;
+
+import java.io.IOException;
+import java.util.Enumeration;
+import java.util.StringTokenizer;
+
+import javax.faces.context.FacesContext;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.alfresco.error.AlfrescoRuntimeException;
+import org.alfresco.web.app.servlet.AuthenticationStatus;
+import org.alfresco.web.app.servlet.BaseServlet;
+import org.alfresco.web.app.servlet.FacesHelper;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+/**
+ * Servlet responsible for processing AJAX requests.
+ * 
+ * The URL to the servlet should be in the form:
+ * <pre>/alfresco/ajax/command/Bean.binding.expression</pre>
+ * <p>
+ * where 'command' is one of 'invoke', 'get' or 'set'.
+ * <p>
+ * TODO: Explain what the commands do...
+ * <p>
+ * Like most Alfresco servlets, the URL may be followed by a valid 'ticket' argument for authentication:
+ * ?ticket=1234567890
+ * 
+ * @author gavinc
+ */
+public class AjaxServlet extends BaseServlet
+{
+   public static final String AJAX_LOG_KEY = "alfresco.ajax";
+   
+   protected enum Command { invoke, get, set};
+   
+   private static final long serialVersionUID = -7654769105419391840L;
+   private static Log logger = LogFactory.getLog(AJAX_LOG_KEY);
+   private static Log headersLogger = LogFactory.getLog(AJAX_LOG_KEY + ".headers");
+   
+   /**
+    * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
+    */
+   protected void service(HttpServletRequest request, HttpServletResponse response)
+      throws ServletException, IOException
+   {
+      try
+      {
+         String uri = request.getRequestURI();
+         
+         if (logger.isDebugEnabled())
+         {
+            String queryString = request.getQueryString();
+            logger.debug("Processing URL: " + uri + 
+                  ((queryString != null && queryString.length() > 0) ? ("?" + queryString) : ""));
+         }
+         
+         // dump the request headers
+         if (headersLogger.isDebugEnabled())
+         {
+            Enumeration headers = request.getHeaderNames();
+            while (headers.hasMoreElements())
+            {
+               String name = (String)headers.nextElement();
+               headersLogger.debug(name + ": " + request.getHeader(name));
+            }
+         }
+         
+         // ************
+         // TODO: Need to send in a flag to method to stop it from redirecting
+         //       to login page, we can then throw an error in here!!
+         
+         AuthenticationStatus status = servletAuthenticate(request, response);
+         if (status == AuthenticationStatus.Failure)
+         {
+            return;
+         }
+         
+         uri = uri.substring(request.getContextPath().length());
+         StringTokenizer t = new StringTokenizer(uri, "/");
+         int tokenCount = t.countTokens();
+         if (tokenCount < 3)
+         {
+            throw new AlfrescoRuntimeException("Servlet URL did not contain all required args: " + uri); 
+         }
+         
+         // skip the servlet name
+         t.nextToken();
+         
+         // retrieve the command from the URL
+         String commandName = t.nextToken();
+         
+         // retrieve the binding expression from the URL
+         String expression = t.nextToken();
+         
+         // setup the faces context
+         FacesContext facesContext = FacesHelper.getFacesContext(request, response, getServletContext());
+         
+         // instantiate the relevant command
+         AjaxCommand command = null;
+         if (Command.invoke.toString().equals(commandName))
+         {
+            command = new InvokeCommand();
+         }
+         else if (Command.get.toString().equals(commandName))
+         {
+            command = new GetCommand();
+         }
+//         else if (Command.set.toString().equals(commandName))
+//         {
+//            command = new SetCommand();
+//         }
+         else
+         {
+            throw new AlfrescoRuntimeException("Unrecognised command received: " + commandName);
+         }
+         
+         // execute the command
+         command.execute(facesContext, expression, request, response);
+      }
+      catch (RuntimeException error)
+      {
+         handleError(response, error);
+      }
+   }
+   
+   /**
+    * Handles any error that occurs during the execution of the servlet
+    * 
+    * @param response The response
+    * @param cause The cause of the error
+    */
+   protected void handleError(HttpServletResponse response, RuntimeException cause)
+      throws ServletException, IOException
+   {
+      // if we can send back the 500 error with the error from the top of the 
+      // stack as the error status message.
+      
+      // NOTE: if we use the built in support for generating error pages for
+      //       500 errors we can tailor the output for AJAX calls so that the
+      //       body of the response can be used to show the error details.
+      
+      if (!response.isCommitted())
+      {
+         // dump the error if debugging is enabled
+         if (logger.isDebugEnabled())
+         {
+            logger.error(cause);
+            Throwable theCause = cause.getCause();
+            if (theCause != null)
+            {
+               logger.error("caused by: ", theCause);
+            }
+         }
+            
+         // extract a message from the exception
+         String msg = cause.getMessage();
+         if (msg == null)
+         {
+            msg = cause.toString();
+         }
+         
+         // send the error
+         response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, msg);
+      }
+      else
+      {
+         // the response has already been comitted, not much we can do but
+         // let the error through and let the container deal with it
+         throw cause;
+      }
+   }
+}

source/java/org/alfresco/web/app/servlet/ajax/BaseAjaxCommand.java

@@ -0,0 +1,19 @@
+package org.alfresco.web.app.servlet.ajax;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+/**
+ * Base class for all Ajax based commands
+ * 
+ * @author gavinc
+ */
+public abstract class BaseAjaxCommand implements AjaxCommand
+{
+   protected static Log logger = LogFactory.getLog(AjaxServlet.AJAX_LOG_KEY);
+   
+   public String makeBindingExpression(String expression)
+   {
+      return "#{" + expression + "}";
+   }
+}

source/java/org/alfresco/web/app/servlet/ajax/GetCommand.java

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+package org.alfresco.web.app.servlet.ajax;
+
+import java.io.IOException;
+
+import javax.faces.context.FacesContext;
+import javax.faces.el.ValueBinding;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.transaction.UserTransaction;
+
+import org.alfresco.error.AlfrescoRuntimeException;
+import org.alfresco.web.bean.repository.Repository;
+
+/**
+ * Command that executes the given value binding expression.
+ * <p>
+ * This command is intended to be used for calling existing managed 
+ * bean methods. The result of the value binding is added to
+ * the response as is i.e. by calling toString(). 
+ * The content type of the response is always text/html.
+ * 
+ * @author gavinc
+ */
+public class GetCommand extends BaseAjaxCommand
+{
+   public void execute(FacesContext facesContext, String expression,
+         HttpServletRequest request, HttpServletResponse response)
+         throws ServletException, IOException
+   {
+      // create the JSF binding expression
+      String bindingExpr = makeBindingExpression(expression);
+      
+      if (logger.isDebugEnabled())
+         logger.debug("Retrieving value from value binding: " + bindingExpr);
+      
+      UserTransaction tx = null;
+      try
+      {
+         // create the value binding
+         ValueBinding binding = facesContext.getApplication().
+               createValueBinding(bindingExpr);
+         
+         if (binding != null)
+         {
+            // setup the transaction
+            tx = Repository.getUserTransaction(facesContext, true);
+            tx.begin();
+            
+            // get the value from the value binding
+            Object value = binding.getValue(facesContext);
+            response.getWriter().write(value.toString());
+            
+            // commit
+            tx.commit();
+         }
+      }
+      catch (Throwable err)
+      {
+         // rollback the transaction
+         try { if (tx != null) {tx.rollback();} } catch (Exception ex) {}
+         
+         throw new AlfrescoRuntimeException("Failed to retrieve value: " + err.getMessage(), err);
+      }
+   }
+}

source/java/org/alfresco/web/app/servlet/ajax/InvokeCommand.java

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+package org.alfresco.web.app.servlet.ajax;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+
+import javax.faces.FactoryFinder;
+import javax.faces.component.UIViewRoot;
+import javax.faces.context.FacesContext;
+import javax.faces.context.ResponseWriter;
+import javax.faces.el.MethodBinding;
+import javax.faces.render.RenderKit;
+import javax.faces.render.RenderKitFactory;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.transaction.UserTransaction;
+
+import org.alfresco.error.AlfrescoRuntimeException;
+import org.alfresco.repo.content.MimetypeMap;
+import org.alfresco.web.bean.repository.Repository;
+
+/**
+ * Command that invokes the method represented by the expression.
+ * <p>
+ * The managed bean method called is responsible for writing the response
+ * by getting hold of the JSF ResponseWriter. Parameters can also be 
+ * retrieved via the JSF ExternalContext object.
+ * <p>
+ * In a future release (if required) annotations may be used to state
+ * what content type to use for the response.
+ * 
+ * @author gavinc
+ */
+public class InvokeCommand extends BaseAjaxCommand
+{
+   public void execute(FacesContext facesContext, String expression,
+         HttpServletRequest request, HttpServletResponse response)
+         throws ServletException, IOException
+   {
+      // setup the JSF response writer.
+      
+      // NOTE: it doesn't seem to matter what the content type of the response is (at least with Dojo), 
+      // it determines it's behaviour from the mimetype specified in the AJAX call on the client,
+      // therefore, for now we will always return a content type of text/html.
+      // In the future we may use annotations on the method to be called to specify what content
+      // type should be used for the response.
+      
+      OutputStream os = response.getOutputStream();
+      UIViewRoot viewRoot = facesContext.getViewRoot();
+      RenderKitFactory renderFactory = (RenderKitFactory)FactoryFinder.
+            getFactory(FactoryFinder.RENDER_KIT_FACTORY);
+      RenderKit renderKit = renderFactory.getRenderKit(facesContext, 
+            viewRoot.getRenderKitId());
+      ResponseWriter writer = renderKit.createResponseWriter(
+            new OutputStreamWriter(os), MimetypeMap.MIMETYPE_HTML, "UTF-8");
+      facesContext.setResponseWriter(writer);
+      response.setContentType(writer.getContentType());
+      
+      // create the JSF binding expression
+      String bindingExpr = makeBindingExpression(expression);
+      
+      if (logger.isDebugEnabled())
+         logger.debug("Invoking method represented by " + bindingExpr);
+      
+      UserTransaction tx = null;
+      try
+      {
+         // create the method binding from the expression
+         MethodBinding binding = facesContext.getApplication().createMethodBinding(
+               bindingExpr, new Class[] {});
+         
+         if (binding != null)
+         {
+            // setup the transaction
+            tx = Repository.getUserTransaction(facesContext);
+            tx.begin();
+            
+            // invoke the method
+            binding.invoke(facesContext, new Object[] {});
+            
+            // commit
+            tx.commit();
+         }
+      }
+      catch (Throwable err)
+      {
+         // rollback the transaction
+         try { if (tx != null) {tx.rollback();} } catch (Exception ex) {}
+         
+         throw new AlfrescoRuntimeException("Failed to execute method: " + err.getMessage(), err);
+      }
+
+      // force the output back to the client
+      writer.close();
+   }
+}

source/java/org/alfresco/web/bean/ajax/BaseAjaxBean.java

@@ -0,0 +1,51 @@
+package org.alfresco.web.bean.ajax;
+
+import java.io.IOException;
+
+import javax.faces.context.FacesContext;
+import javax.faces.context.ResponseWriter;
+
+/**
+ * Base class for all Ajax managed beans.
+ * 
+ * It is not necessary to extend this bean but it provides 
+ * helper methods.
+ * 
+ * @author gavinc
+ */
+public abstract class BaseAjaxBean
+{
+   private ResponseWriter writer;
+   
+   /**
+    * Writes the given string to the response writer for this bean
+    * 
+    * @param str The string to send back to the client
+    */
+   public void write(String str)
+   {
+      try
+      {
+         getWriter().write(str);
+      }
+      catch (IOException ioe)
+      {
+         // not much we can do here, ignore
+      }
+   }
+   
+   /**
+    * Returns the ResponseWriter for this bean
+    * 
+    * @return The JSF ResponseWriter
+    */
+   public ResponseWriter getWriter()
+   {
+      if (this.writer == null)
+      {
+         this.writer = FacesContext.getCurrentInstance().getResponseWriter();
+      }
+      
+      return this.writer;
+   }
+}