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Groovy 1.7.0
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groovy.servlet
Class TemplateServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          groovy.servlet.AbstractHttpServlet
              groovy.servlet.TemplateServlet

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

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
see:
TemplateServlet#setVariables(ServletBinding)
author:
Christian Stein
author:
Guillaume Laforge
version:
2.0

Nested Class Summary
class TemplateServlet.TemplateCacheEntry

Simple cache entry that validates against last modified and length attributes of the specified file.

 
Field Summary
 
Fields inherited from class AbstractHttpServlet
encoding, reflection, resourceNameMatcher, resourceNameReplaceAll, resourceNameReplacement, servletContext, verbose
 
Constructor Summary
TemplateServlet()

 
Method Summary
def TemplateServlet()

Create new TemplateSerlvet.

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 AbstractHttpServlet
getResourceConnection, getScriptUri, getScriptUriAsFile, init, setVariables
 
Methods inherited from class HttpServlet
service, log, log, init, init, destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, wait, wait, wait, hashCode, getClass, equals, toString, notify, notifyAll
 
Methods inherited from class GenericServlet
log, log, init, init, destroy, service, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, wait, wait, wait, hashCode, getClass, equals, toString, notify, notifyAll
 
Methods inherited from class Object
wait, wait, wait, hashCode, getClass, equals, toString, notify, notifyAll
 

Constructor Detail

TemplateServlet

TemplateServlet()

 
Method Detail

TemplateServlet

public def TemplateServlet()
Create new TemplateSerlvet.

getTemplate

protected Template getTemplate(File file)
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.

return:
The template that will produce the response text.
param:
file The HttpServletRequest.
throws:
ServletException If the request specified an invalid template source file

init

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

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

param:
config Passed by the servlet container.
throws:
ServletException if this method encountered difficulties
see:
TemplateServlet#initTemplateEngine(ServletConfig)

initTemplateEngine

protected TemplateEngine initTemplateEngine(ServletConfig config)
Creates the template engine. Called by TemplateServlet#init(ServletConfig) and returns just new groovy.text.SimpleTemplateEngine() if the init parameter template.engine is not set by the container configuration.
param:
config Current serlvet configuration passed by the container.
return:
The underlying template engine or null on error.

service

public void service(HttpServletRequest request, HttpServletResponse response)
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.

param:
request The http request.
param:
response The http response.
throws:
IOException if an input or output error occurs while the servlet is handling the HTTP request
throws:
ServletException if the HTTP request cannot be handled

 

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