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groovy.servlet
Class TemplateServlet

java.lang.Object
  extended by javax.servlet.GenericServlet
      extended by javax.servlet.http.HttpServlet
          extended by groovy.servlet.AbstractHttpServlet
              extended by groovy.servlet.TemplateServlet
All Implemented Interfaces:
ResourceConnector, Serializable, Servlet, ServletConfig
public class TemplateServlet
extends AbstractHttpServlet

A generic servlet for serving (mostly HTML) templates.

It delegates work to a groovy.text.TemplateEngine implementation processing HTTP requests.

Usage

helloworld.html is a headless HTML-like template 

  <html>
    <body>
      <% 3.times { %>
        Hello World!
      <% } %>
      <br>
    </body>
  </html>
Minimal web.xml example serving HTML-like templates 

 <web-app>
   <servlet>
     <servlet-name>template</servlet-name>
     <servlet-class>groovy.servlet.TemplateServlet</servlet-class>
   </servlet>
   <servlet-mapping>
     <servlet-name>template</servlet-name>
     <url-pattern>*.html</url-pattern>
   </servlet-mapping>
 </web-app>

Template engine configuration

By default, the TemplateServer uses the SimpleTemplateEngine which interprets JSP-like templates. The init parameter template.engine defines the fully qualified class name of the template to use: 

   template.engine = [empty] - equals groovy.text.SimpleTemplateEngine
   template.engine = groovy.text.SimpleTemplateEngine
   template.engine = groovy.text.GStringTemplateEngine
   template.engine = groovy.text.XmlTemplateEngine

Servlet Init Parameters

Logging and extra-output options

This implementation provides a verbosity flag switching log statements. The servlet init parameter name is: 

   generated.by = true(default) | false

Groovy Source Encoding Parameter

The following servlet init parameter name can be used to specify the encoding TemplateServlet will use to read the template groovy source files: 

   groovy.source.encoding

Version:
2.0
Author:
Christian Stein, Guillaume Laforge
See Also:
AbstractHttpServlet.setVariables(ServletBinding), Serialized Form

Field Summary
 
Fields inherited from class groovy.servlet.AbstractHttpServlet
CONTENT_TYPE_TEXT_HTML, encoding, INC_PATH_INFO, INC_REQUEST_URI, INC_SERVLET_PATH, reflection, resourceNameMatcher, resourceNameReplaceAll, resourceNameReplacement, servletContext, verbose
 
Constructor Summary
TemplateServlet()
          Create new TemplateSerlvet.
 
Method Summary
protected  Template getTemplate(File file)
          Gets the template created by the underlying engine parsing the request.
 void init(ServletConfig config)
          Initializes the servlet from hints the container passes.
protected  TemplateEngine initTemplateEngine(ServletConfig config)
          Creates the template engine.
 void service(HttpServletRequest request, HttpServletResponse response)
          Services the request with a response.
 
Methods inherited from class groovy.servlet.AbstractHttpServlet
getResourceConnection, getScriptUri, getScriptUriAsFile, setVariables
 
Methods inherited from class javax.servlet.http.HttpServlet
doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service
 
Methods inherited from class javax.servlet.GenericServlet
destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

TemplateServlet

public TemplateServlet()
Create new TemplateSerlvet.

Method Detail

getTemplate

protected Template getTemplate(File file)
                        throws ServletException
Gets the template created by the underlying engine parsing the request.

This method looks up a simple (weak) hash map for an existing template object that matches the source file. If the source file didn't change in length and its last modified stamp hasn't changed compared to a precompiled template object, this template is used. Otherwise, there is no or an invalid template object cache entry, a new one is created by the underlying template engine. This new instance is put to the cache for consecutive calls.

Parameters:
file - The HttpServletRequest.
Returns:
The template that will produce the response text.
Throws:
ServletException - If the request specified an invalid template source file

init

public void init(ServletConfig config)
          throws ServletException
Initializes the servlet from hints the container passes.

Delegates to sub-init methods and parses the following parameters:

Specified by:
init in interface Servlet
Overrides:
init in class AbstractHttpServlet
Parameters:
config - Passed by the servlet container.
Throws:
ServletException - if this method encountered difficulties
See Also:
initTemplateEngine(ServletConfig)

initTemplateEngine

protected TemplateEngine initTemplateEngine(ServletConfig config)
Creates the template engine. Called by init(ServletConfig) and returns just new groovy.text.SimpleTemplateEngine() if the init parameter template.engine is not set by the container configuration.

Parameters:
config - Current serlvet configuration passed by the container.
Returns:
The underlying template engine or null on error.

service

public void service(HttpServletRequest request,
                    HttpServletResponse response)
             throws ServletException,
                    IOException
Services the request with a response.

First the request is parsed for the source file uri. If the specified file could not be found or can not be read an error message is sent as response.

Overrides:
service in class HttpServlet
Parameters:
request - The http request.
response - The http response.
Throws:
IOException - if an input or output error occurs while the servlet is handling the HTTP request
ServletException - if the HTTP request cannot be handled
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