org.apache.velocity.tools.view

Class VelocityLayoutServlet

java.lang.Object

HttpServlet

org.apache.velocity.tools.view.VelocityViewServlet

org.apache.velocity.tools.view.VelocityLayoutServlet

Direct Known Subclasses:

VelocityLayoutServlet

public class VelocityLayoutServlet
extends VelocityViewServlet

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

Version:

$Id: VelocityLayoutServlet.java 823236 2009-10-08 17:24:48Z nbubna $

Author:

Nathan Bubna

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	DEFAULT_DEFAULT_LAYOUT The default filename for the servlet's default layout
static java.lang.String	DEFAULT_ERROR_TEMPLATE The default error template's filename.
static java.lang.String	DEFAULT_LAYOUT_DIR The default layout directory
protected java.lang.String	defaultLayout
protected java.lang.String	errorTemplate
static java.lang.String	KEY_ERROR_CAUSE The context key that holds the Throwable that broke the rendering of the requested screen.
static java.lang.String	KEY_ERROR_INVOCATION_EXCEPTION The context key that holds the MethodInvocationException that broke the rendering of the requested screen.
static java.lang.String	KEY_ERROR_STACKTRACE The context key that holds the stack trace of the error that broke the rendering of the requested screen.
static java.lang.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 java.lang.String	KEY_SCREEN_CONTENT The context key that will hold the content of the screen.
protected java.lang.String	layoutDir
static java.lang.String	PROPERTY_DEFAULT_LAYOUT The velocity.properties key for specifying the servlet's default layout template's filename.
static java.lang.String	PROPERTY_ERROR_TEMPLATE The velocity.properties key for specifying the servlet's error template.
static java.lang.String	PROPERTY_LAYOUT_DIR The velocity.properties key for specifying the relative directory holding layout templates.
private static long	serialVersionUID serial version id

Fields inherited from class org.apache.velocity.tools.view.VelocityViewServlet

BUFFER_OUTPUT_PARAM

Constructor Summary

Constructors

Constructor and Description
VelocityLayoutServlet()

Method Summary

Methods

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

Methods inherited from class org.apache.velocity.tools.view.VelocityViewServlet

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

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

serial version id

See Also:

Constant Field Values

PROPERTY_ERROR_TEMPLATE

public static final java.lang.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 java.lang.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 java.lang.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 java.lang.String DEFAULT_ERROR_TEMPLATE

The default error template's filename.

See Also:

Constant Field Values

DEFAULT_LAYOUT_DIR

public static final java.lang.String DEFAULT_LAYOUT_DIR

The default layout directory

See Also:

Constant Field Values

DEFAULT_DEFAULT_LAYOUT

public static final java.lang.String DEFAULT_DEFAULT_LAYOUT

The default filename for the servlet's default layout

See Also:

Constant Field Values

KEY_SCREEN_CONTENT

public static final java.lang.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 java.lang.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 java.lang.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 java.lang.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 java.lang.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

errorTemplate

protected java.lang.String errorTemplate

layoutDir

protected java.lang.String layoutDir

defaultLayout

protected java.lang.String defaultLayout

Constructor Detail

VelocityLayoutServlet

public VelocityLayoutServlet()

Method Detail

init

public void init(ServletConfig config)
          throws ServletException

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

Overrides:

init in class VelocityViewServlet

Parameters:

config - servlet configuration parameters

Throws:

ServletException

fillContext

protected void fillContext(Context ctx,
               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 java.lang.String findLayout(HttpServletRequest request)

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

mergeTemplate

protected void mergeTemplate(Template template,
                 Context context,
                 HttpServletResponse response)
                      throws java.io.IOException

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

Overrides:

mergeTemplate in class VelocityViewServlet

Throws:

java.io.IOException

error

protected void error(HttpServletRequest request,
         HttpServletResponse response,
         java.lang.Throwable e)

Overrides VelocityViewServlet to display user's custom error template

Overrides:

error in class VelocityViewServlet

Parameters:

request - original HttpServletRequest from servlet container.

response - HttpServletResponse object from servlet container.

e - Exception that was thrown by some other part of process.