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Posted to dev@velocity.apache.org by ge...@apache.org on 2001/03/12 05:03:59 UTC
cvs commit: jakarta-velocity/src/java/org/apache/velocity/servlet VelocityServlet.java
geirm 01/03/11 20:03:59
Modified: src/java/org/apache/velocity/servlet VelocityServlet.java
Log:
A few changes that were in the queue :
0) A bit of javadoc on the class javadoc section, highlighting the
methods a user can overload to get access to useful parts of the
request processing.
1) Added a 'loadConfiguration()' call to allow derived classes to alter
or add to the properties set used to configure the runtime. I moved
the file processing code into this routine, as it seems more generalized
to locate that kind of thing there, and further, it's presumptuous to
assume that the user cares about the file anyway (the could be loading
config info from somewhere else...) or that there even is a file.
2) Changed error() from 'private final' to 'protected' to allow derived
classes to do something more useful in the event of an error. Also
put into the default output that the message was coming from
VelocityServlet (easier for beginners), and also dumped the stacktrace
from the exception to make debugging even more fun and exciting than
debugging normally is.
Anything wrong, I am sure I will hear about it :)
Revision Changes Path
1.24 +115 -25 jakarta-velocity/src/java/org/apache/velocity/servlet/VelocityServlet.java
Index: VelocityServlet.java
===================================================================
RCS file: /home/cvs/jakarta-velocity/src/java/org/apache/velocity/servlet/VelocityServlet.java,v
retrieving revision 1.23
retrieving revision 1.24
diff -u -r1.23 -r1.24
--- VelocityServlet.java 2001/03/05 11:47:25 1.23
+++ VelocityServlet.java 2001/03/12 04:03:59 1.24
@@ -3,7 +3,7 @@
/*
* The Apache Software License, Version 1.1
*
- * Copyright (c) 2001 The Apache Software Foundation. All rights
+ * Copyright (c) 2000-2001 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -56,11 +56,15 @@
import java.io.IOException;
import java.io.PrintWriter;
+import java.io.StringWriter;
import java.io.Writer;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
-import java.util.Stack;
+import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
@@ -95,6 +99,20 @@
* "res" - The HttpServletResponse object
* </pre>
*
+ * There are other methods you can override to access, alter or control
+ * any part of the request processing chain. Please see the javadocs for
+ * more information on :
+ * <ul>
+ * <li> loadConfiguration() : for setting up the Velocity runtime
+ * <li> createContext() : for creating and loading the Context
+ * <li> setContentType() : for changing the content type on a request
+ * by request basis
+ * <li> handleRequest() : you <b>must</b> implement this
+ * <li> mergeTemplate() : the template rendering process
+ * <li> requestCleanup() : post rendering resource or other cleanup
+ * <li> error() : error handling
+ * </ul>
+ * <br>
* If you put a contentType object into the context within either your
* serlvet or within your template, then that will be used to override
* the default content type specified in the properties file.
@@ -104,7 +122,7 @@
* @author Dave Bryson
* @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
* @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
- * $Id: VelocityServlet.java,v 1.23 2001/03/05 11:47:25 jvanzyl Exp $
+ * $Id: VelocityServlet.java,v 1.24 2001/03/12 04:03:59 geirm Exp $
*/
public abstract class VelocityServlet extends HttpServlet
{
@@ -157,7 +175,70 @@
throws ServletException
{
super.init( config );
-
+
+ try
+ {
+ /*
+ * call the overridable method to allow the
+ * derived classes a shot at altering the configuration
+ * before initializing Runtime
+ */
+
+ Properties props = loadConfiguration( config );
+
+ Runtime.init( props );
+
+ defaultContentType =
+ Runtime.getString(Runtime.DEFAULT_CONTENT_TYPE, "text/html");
+
+ encoding = Runtime.getString(Runtime.TEMPLATE_ENCODING, "8859_1");
+ }
+ catch( Exception e )
+ {
+ throw new ServletException("Error configuring the loader: " + e);
+ }
+ }
+
+ /**
+ * Loads the configuration information and returns that
+ * information as a Properties, which will be used to
+ * initialize the Velocity runtime.
+ * <br><br>
+ * Currently, this method gets the initialization parameter
+ * VelocityServlet.INIT_PROPS_KEY, which should be a file containing
+ * the configuration information.
+ * <br><br>
+ * To configure your Servlet Spec 2.2 compliant servlet runner to pass this
+ * to you, put the following in your WEB-INF/web.xml file
+ * <br>
+ * <pre>
+ * <servlet >
+ * <servlet-name> YourServlet </servlet-name>
+ * <servlet-class> your.package.YourServlet </servlet-class>
+ * <init-param>
+ * <param-name> properties </param-name>
+ * <param-value> velocity.properties </param-value>
+ * </init-param>
+ * </servlet>
+ * </pre>
+ *
+ * Derived classes may do the same, or take advantage of this code to do the loading for them via :
+ * <pre>
+ * Properties p = super.loadConfiguration( config );
+ * </pre>
+ * and then add or modify the configuration values from the file.
+ * <br>
+ *
+ * @param config ServletConfig passed to the servlets init() function
+ * Can be used to access the real path via ServletContext (hint)
+ * @return java.util.Properties loaded with configuration values to be used
+ * to initialize the Velocity runtime.
+ * @throws FileNotFoundException if a specified file is not found.
+ * @throws IOException I/O problem accessing the specified file, if specified.
+ */
+ protected Properties loadConfiguration(ServletConfig config )
+ throws IOException, FileNotFoundException
+ {
String propsFile = config.getInitParameter(INIT_PROPS_KEY);
/*
@@ -169,6 +250,8 @@
* if this will break other servlet engines, but it probably
* shouldn't since WAR files are the future anyways.
*/
+
+ Properties p = new Properties();
if ( propsFile != null )
{
@@ -178,23 +261,13 @@
{
propsFile = realPath;
}
- }
- try
- {
- Runtime.init(propsFile);
-
- defaultContentType =
- Runtime.getString(Runtime.DEFAULT_CONTENT_TYPE, "text/html");
-
- encoding = Runtime.getString(Runtime.TEMPLATE_ENCODING, "8859_1");
- }
- catch( Exception e )
- {
- throw new ServletException("Error configuring the loader: " + e);
+ p.load( new FileInputStream(propsFile) );
}
+
+ return p;
}
-
+
/**
* Handles GET - calls doRequest()
*/
@@ -265,7 +338,12 @@
}
catch (Exception e)
{
- error ( response, e.getMessage());
+ /*
+ * call the error handler to let the derived class
+ * do something useful with this failure.
+ */
+
+ error( request, response, e);
}
}
@@ -350,8 +428,8 @@
}
/**
- * returns a context suitable to pass to the handleRequest() method
- *
+ * Returns a context suitable to pass to the handleRequest() method
+ * <br><br>
* Default implementation will create a VelocityContext object,
* put the HttpServletRequest and HttpServletResponse
* into the context accessable via the keys VelocityServlet.REQUEST and
@@ -409,16 +487,28 @@
protected abstract Template handleRequest( Context ctx );
/**
- * Send an error message to the client.
+ * Invoked when there is an error thrown in any part of doRequest() processing.
+ * <br><br>
+ * Default will send a simple HTML response indicating there was a problem.
+ *
+ * @param request original HttpServletRequest from servlet container.
+ * @param response HttpServletResponse object from servlet container.
+ * @param cause Exception that was thrown by some other part of process.
*/
- private final void error( ServletResponse response, String message )
+ protected void error( HttpServletRequest request, HttpServletResponse response, Exception cause )
throws ServletException, IOException
{
StringBuffer html = new StringBuffer();
html.append("<html>");
html.append("<body bgcolor=\"#ffffff\">");
- html.append("<h2>Error processing the template</h2>");
- html.append(message);
+ html.append("<h2>VelocityServlet : Error processing the template</h2>");
+ html.append( cause );
+ html.append("<br>");
+
+ StringWriter sw = new StringWriter();
+ cause.printStackTrace( new PrintWriter( sw ) );
+
+ html.append( sw.toString() );
html.append("</body>");
html.append("</html>");
response.getOutputStream().print( html.toString() );