net.sourceforge.stripes.controller

Class DynamicMappingFilter

java.lang.Object

net.sourceforge.stripes.controller.DynamicMappingFilter

All Implemented Interfaces:

Filter

public class DynamicMappingFilter
extends Object
implements Filter

A servlet filter that dynamically maps URLs to ActionBeans. This filter can be used to allow Stripes to dispatch requests to ActionBeans based on their URL binding, even if the URL to which they are bound is not explicitly mapped in web.xml.

One caveat must be observed when using this filter. This filter MUST be the last filter in the filter chain. When it dynamically maps an ActionBean to a URL, the filter chain is interrupted.

StripesFilter and/or DispatcherServlet may be declared in web.xml, but neither is required for this filter to work. If you choose not to declare StripesFilter in web.xml, then this filter should be configured the way you would normally configure StripesFilter. However, some resources, such as JSPs, may require access to the Stripes Configuration through StripesFilter. If you intend to access JSPs directly, then StripesFilter should be explicitly mapped to *.jsp.

This filter takes the following approach to determining when to dispatch an ActionBean:

1. Allow the request to process normally, trapping any HTTP errors that are returned.
2. If no error was returned then do nothing, allowing the request to complete successfully. If any error other than 404 was returned then send the error through. Otherwise ...
3. Check the ActionResolver to see if an ActionBean is mapped to the URL. If not, then send the 404 error through. Otherwise...
4. Invoke StripesFilter and DispatcherServlet

One benefit of this approach is that static resources can be delivered from the same namespace to which an ActionBean is mapped using clean URLs. (For more information on clean URLs, see UrlBinding.) For example, if your UserActionBean is mapped to @UrlBinding("/user/{id}/{$event}") and you have a static file at /user/icon.gif, then your icon will be delivered correctly because the initial request will not have returned a 404 error.

The IncludeBufferSize initialization parameter (optional, default 1024) sets the number of characters to be buffered by DynamicMappingFilter.TempBufferWriter for include requests. See DynamicMappingFilter.TempBufferWriter for more information.

This is the suggested mapping for this filter in web.xml.

  <filter>
      <description>Dynamically maps URLs to ActionBeans.</description>
      <display-name>Stripes Dynamic Mapping Filter</display-name>
      <filter-name>DynamicMappingFilter</filter-name>
      <filter-class>
          net.sourceforge.stripes.controller.DynamicMappingFilter
      </filter-class>
      <init-param>
          <param-name>ActionResolver.Packages</param-name>
          <param-value>com.yourcompany.stripes.action</param-value>
      </init-param>
  </filter>
  
  <filter-mapping>
      <filter-name>DynamicMappingFilter</filter-name>
      <url-pattern>/*</url-pattern>
      <dispatcher>REQUEST</dispatcher>
      <dispatcher>FORWARD</dispatcher>
      <dispatcher>INCLUDE</dispatcher>
  </filter-mapping>
 

Since:

Stripes 1.5

Author:

Ben Gunter

See Also:

UrlBinding

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DynamicMappingFilter.ErrorTrappingResponseWrapper An HttpServletResponseWrapper that traps HTTP errors by overriding sendError(int, ..).
static class	DynamicMappingFilter.TempBufferWriter A Writer that passes characters to a PrintWriter.

Field Summary

Fields

Modifier and Type	Field and Description
static String	CONTEXT_KEY_STRIPES_FILTER The attribute name used to store a reference to StripesFilter in the servlet context.
static String	INCLUDE_BUFFER_SIZE_PARAM The name of the init-param that can be used to set the size of the buffer used by DynamicMappingFilter.TempBufferWriter before it overflows.

Constructor Summary

Constructors

Constructor and Description
DynamicMappingFilter()

Method Summary

Methods

Modifier and Type	Method and Description
protected void	createStripesFilter(FilterConfig config) Create and initialize an instance of StripesFilter with the given configuration.
void	destroy()
void	doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
protected <T> T	eval(String expression, Node source, QName returnType) Evaluate an xpath expression against a DOM Node and return the result.
protected Map<String,String>	getFilterParameters(Node filterNode) Get the initialization parameters for a filter declared in web.xml.
protected List<String>	getFilterUrlPatterns(Node filterNode) Get all the URL patterns to which a filter is mapped in web.xml.
protected String	getRequestURI(HttpServletRequest request) Deprecated. Use HttpUtil.getRequestedPath(HttpServletRequest) instead.
protected StripesFilter	getStripesFilter() Get a reference to StripesFilter.
void	init(FilterConfig config)
protected void	initStripesFilter(HttpServletRequest request, HttpServletResponse response) The servlet spec allows a container to wait until a filter is required to process a request before it initializes the filter.
protected void	issueRequests(List<String> patterns, HttpServletRequest request, HttpServletResponse response) Issue a series of requests in an attempt to force an invocation (and initialization) of StripesFilter in the application context.
protected Document	parseWebXml() Parse the application's web.xml file and return a DOM Document.
void	requestRemotely(HttpServletRequest request, String relativePath) Issue a new request to a path relative to the request's context.

Methods inherited from class java.lang.Object

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

Field Detail

INCLUDE_BUFFER_SIZE_PARAM

public static final String INCLUDE_BUFFER_SIZE_PARAM

The name of the init-param that can be used to set the size of the buffer used by DynamicMappingFilter.TempBufferWriter before it overflows.

See Also:

Constant Field Values

CONTEXT_KEY_STRIPES_FILTER

public static final String CONTEXT_KEY_STRIPES_FILTER

The attribute name used to store a reference to StripesFilter in the servlet context.

Constructor Detail

DynamicMappingFilter

public DynamicMappingFilter()

Method Detail

init

public void init(FilterConfig config)
          throws ServletException

Specified by:

init in interface Filter

Throws:

ServletException

destroy

public void destroy()

Specified by:

destroy in interface Filter

doFilter

public void doFilter(ServletRequest request,
            ServletResponse response,
            FilterChain chain)
              throws IOException,
                     ServletException

Specified by:

doFilter in interface Filter

Throws:

IOException

ServletException

getRequestURI

@Deprecated
protected String getRequestURI(HttpServletRequest request)

Deprecated. Use HttpUtil.getRequestedPath(HttpServletRequest) instead.

Get the context-relative URI of the current include, forward or request.

getStripesFilter

protected StripesFilter getStripesFilter()

Get a reference to StripesFilter. The first time this method is called, the reference will be looked up in the servlet context and cached in the stripesFilter field.

initStripesFilter

protected void initStripesFilter(HttpServletRequest request,
                     HttpServletResponse response)
                          throws ServletException

The servlet spec allows a container to wait until a filter is required to process a request before it initializes the filter. Since we need to get a reference to StripesFilter from the servlet context, we really need StripesFilter to have been initialized at the time we process our first request. If that didn't happen automatically, this method does its best to force it to happen.

Parameters:

request - The current request

response - The current response

Throws:

ServletException - If anything goes wrong that simply can't be ignored.

parseWebXml

protected Document parseWebXml()
                        throws SAXException,
                               IOException,
                               ParserConfigurationException

Parse the application's web.xml file and return a DOM Document.

Throws:

ParserConfigurationException - If thrown by the XML parser

IOException - If thrown by the XML parser

SAXException - If thrown by the XML parser

eval

protected <T> T eval(String expression,
         Node source,
         QName returnType)
          throws XPathExpressionException

Evaluate an xpath expression against a DOM Node and return the result.

Parameters:

expression - The expression to evaluate

source - The node against which the expression will be evaluated

returnType - One of the constants defined in XPathConstants

Returns:

The result returned by XPath.evaluate(String, Object, QName)

Throws:

XPathExpressionException - If the xpath expression is invalid

getFilterUrlPatterns

protected List<String> getFilterUrlPatterns(Node filterNode)
                                     throws XPathExpressionException

Get all the URL patterns to which a filter is mapped in web.xml. This includes direct mappings using filter-mapping/url-pattern and indirect mappings using filter-mapping/servlet-name and servlet-mapping/url-pattern.

Parameters:

filterNode - The DOM (<filter>) Node containing the filter declaration from web.xml

Returns:

A list of all the patterns to which the filter is mapped

Throws:

XPathExpressionException - In case of failure evaluating an xpath expression

getFilterParameters

protected Map<String,String> getFilterParameters(Node filterNode)
                                          throws XPathExpressionException

Get the initialization parameters for a filter declared in web.xml.

Parameters:

filterNode - The DOM (<filter>) Node containing the filter declaration from web.xml

Returns:

A map of parameter names to parameter values

Throws:

XPathExpressionException - In case of failure evaluation an xpath expression

createStripesFilter

protected void createStripesFilter(FilterConfig config)
                            throws ServletException

Create and initialize an instance of StripesFilter with the given configuration.

Parameters:

config - The filter configuration

Throws:

ServletException - If initialization of the filter fails

issueRequests

protected void issueRequests(List<String> patterns,
                 HttpServletRequest request,
                 HttpServletResponse response)

Issue a series of requests in an attempt to force an invocation (and initialization) of StripesFilter in the application context. All patterns will be requested first with an internal forward, then an include and finally with a brand new request to the address and port returned by ServletRequest.getLocalAddr() and ServletRequest.getLocalPort(), respectively.

Parameters:

patterns - The list of patterns to request, as specified by url-pattern elements in web.xml

request - The current request, required to process a forward or include

response - The current response, required to process a forward or include

requestRemotely

public void requestRemotely(HttpServletRequest request,
                   String relativePath)

Issue a new request to a path relative to the request's context. The connection is made to the address and port returned by ServletRequest.getLocalAddr() and ServletRequest.getLocalPort(), respectively.

Parameters:

request - The current request

relativePath - The context-relative path to request