Class VelocityLayoutServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

org.apache.velocity.tools.view.VelocityViewServlet

org.apache.velocity.tools.view.VelocityLayoutServlet

All Implemented Interfaces:

Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public class VelocityLayoutServlet
extends VelocityViewServlet

Extension of the VelocityViewServlet to perform "two-pass" layout rendering and allow for a customized error screen.

Version:

$Id$

Author:

Nathan Bubna

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final String	DEFAULT_DEFAULT_LAYOUT	The default filename for the servlet's default layout
static final String	DEFAULT_ERROR_TEMPLATE	The default error template's filename.
static final String	DEFAULT_LAYOUT_DIR	The default layout directory
protected String	defaultLayout
protected String	errorTemplate
static final String	KEY_ERROR_CAUSE	The context key that holds the Throwable that broke the rendering of the requested screen.
static final String	KEY_ERROR_INVOCATION_EXCEPTION	The context key that holds the MethodInvocationException that broke the rendering of the requested screen.
static final String	KEY_ERROR_STACKTRACE	The context key that holds the stack trace of the error that broke the rendering of the requested screen.
static final String	KEY_LAYOUT	The context/parameter key used to specify an alternate layout to be used for a request instead of the default layout.
static final String	KEY_SCREEN_CONTENT	The context key that will hold the content of the screen.
protected String	layoutDir
static final String	PROPERTY_DEFAULT_LAYOUT	The velocity.properties key for specifying the servlet's default layout template's filename.
static final String	PROPERTY_DYNAMIC_LAYOUT	The velocity.properties key for specifying whether dynamic layout change is allowed
static final String	PROPERTY_ERROR_TEMPLATE	The velocity.properties key for specifying the servlet's error template.
static final String	PROPERTY_LAYOUT_DIR	The velocity.properties key for specifying the relative directory holding layout templates.

Fields inherited from class VelocityViewServlet

BUFFER_OUTPUT_PARAM

Constructor Summary

Constructors

Constructor	Description
VelocityLayoutServlet()

Method Summary

Modifier and Type	Method	Description
protected void	error(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, Throwable e)	Overrides VelocityViewServlet to display user's custom error template
protected void	fillContext(org.apache.velocity.context.Context ctx, javax.servlet.http.HttpServletRequest request)	Overrides VelocityViewServlet to check the request for an alternate layout
protected String	findLayout(javax.servlet.http.HttpServletRequest request)	Searches for a non-default layout to be used for this request.
void	init(javax.servlet.ServletConfig config)	Initializes Velocity, the view servlet and checks for changes to the initial layout configuration.
protected void	mergeTemplate(org.apache.velocity.Template template, org.apache.velocity.context.Context context, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)	Overrides VelocityViewServlet.mergeTemplate to do a two-pass render for handling layouts

Methods inherited from class VelocityViewServlet

createContext, doGet, doPost, doRequest, findInitParameter, getLog, getOutputWriter, getTemplate, getTemplate, getVelocityProperty, getVelocityView, handleRequest, initRequest, manageResourceNotFound, mergeTemplate, requestCleanup, setContentType, setVelocityView

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

PROPERTY_ERROR_TEMPLATE

public static final String PROPERTY_ERROR_TEMPLATE

The velocity.properties key for specifying the servlet's error template.

See Also:

• Constant Field Values

PROPERTY_LAYOUT_DIR

public static final String PROPERTY_LAYOUT_DIR

The velocity.properties key for specifying the relative directory holding layout templates.

See Also:

• Constant Field Values

PROPERTY_DEFAULT_LAYOUT

public static final String PROPERTY_DEFAULT_LAYOUT

The velocity.properties key for specifying the servlet's default layout template's filename.

See Also:

• Constant Field Values

DEFAULT_ERROR_TEMPLATE

public static final String DEFAULT_ERROR_TEMPLATE

The default error template's filename.

See Also:

• Constant Field Values

DEFAULT_LAYOUT_DIR

public static final String DEFAULT_LAYOUT_DIR

The default layout directory

See Also:

• Constant Field Values

DEFAULT_DEFAULT_LAYOUT

public static final String DEFAULT_DEFAULT_LAYOUT

The default filename for the servlet's default layout

See Also:

• Constant Field Values

KEY_SCREEN_CONTENT

public static final String KEY_SCREEN_CONTENT

The context key that will hold the content of the screen. This key ($screen_content) must be present in the layout template for the current screen to be rendered.

See Also:

• Constant Field Values

KEY_LAYOUT

public static final String KEY_LAYOUT

The context/parameter key used to specify an alternate layout to be used for a request instead of the default layout.

See Also:

• Constant Field Values

KEY_ERROR_CAUSE

public static final String KEY_ERROR_CAUSE

The context key that holds the Throwable that broke the rendering of the requested screen.

See Also:

• Constant Field Values

KEY_ERROR_STACKTRACE

public static final String KEY_ERROR_STACKTRACE

The context key that holds the stack trace of the error that broke the rendering of the requested screen.

See Also:

• Constant Field Values

KEY_ERROR_INVOCATION_EXCEPTION

public static final String KEY_ERROR_INVOCATION_EXCEPTION

The context key that holds the MethodInvocationException that broke the rendering of the requested screen. If this value is placed in the context, then $error_cause will hold the error that this invocation exception is wrapping.

See Also:

• Constant Field Values

PROPERTY_DYNAMIC_LAYOUT

public static final String PROPERTY_DYNAMIC_LAYOUT

The velocity.properties key for specifying whether dynamic layout change is allowed

See Also:

• Constant Field Values

errorTemplate

protected String errorTemplate

layoutDir

protected String layoutDir

defaultLayout

protected String defaultLayout

Constructor Details

VelocityLayoutServlet

public VelocityLayoutServlet()

Method Details

init

public void init(javax.servlet.ServletConfig config)
          throws javax.servlet.ServletException

Initializes Velocity, the view servlet and checks for changes to the initial layout configuration.

Specified by:

init in interface javax.servlet.Servlet

Overrides:

init in class VelocityViewServlet

Parameters:

config - servlet configuration parameters

Throws:

javax.servlet.ServletException

fillContext

protected void fillContext(org.apache.velocity.context.Context ctx,
 javax.servlet.http.HttpServletRequest request)

Overrides VelocityViewServlet to check the request for an alternate layout

Overrides:

fillContext in class VelocityViewServlet

Parameters:

ctx - context for this request

request - client request

findLayout

protected String findLayout(javax.servlet.http.HttpServletRequest request)

Searches for a non-default layout to be used for this request. This implementation checks the request parameters and attributes.

Parameters:

request - servlet request

Returns:

layout name or null

mergeTemplate

protected void mergeTemplate(org.apache.velocity.Template template,
 org.apache.velocity.context.Context context,
 javax.servlet.http.HttpServletRequest request,
 javax.servlet.http.HttpServletResponse response)
                      throws IOException

Overrides VelocityViewServlet.mergeTemplate to do a two-pass render for handling layouts

Overrides:

mergeTemplate in class VelocityViewServlet

Parameters:

template - Template object

context - Velocity context

request - servlet request

response - servlet response

Throws:

IOException

error

protected void error(javax.servlet.http.HttpServletRequest request,
 javax.servlet.http.HttpServletResponse response,
 Throwable e)

Overrides VelocityViewServlet to display user's custom error template

Overrides:

error in class VelocityViewServlet

Parameters:

request - servlet request

response - servlet response

e - thrown error