Java Web Application Development With Click Framework/Quick Start

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This section discusses how to get a Click web application up quickly. This section will not discuss how to configure your build system or IDE, but will focus on all the basic pieces you need to get a Click application running.

The following topics are covered:

Web Application Structure[edit]

First up add a click.xml and web.xml configuration file to your applications WEB-INF directory:

Click application configuration files
  • WEB-INF/click.xml - Application Configuration
  • WEB-INF/web.xml - Servlet Configuration

click.xml[edit]

Your click.xml file should contain:

<?xml version="1.0" encoding="UTF-8"?>
<click-app>
 
  <pages package="com.quickstart.page"/>
 
</click-app>

web.xml[edit]

Your web.xml file should contain:

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
 
  <servlet>
    <servlet-name>click-servlet</servlet-name>
    <servlet-class>net.sf.click.ClickServlet</servlet-class>
    <load-on-startup>0</load-on-startup>
  </servlet>
 
  <servlet-mapping>
    <servlet-name>click-servlet</servlet-name>
    <url-pattern>*.htm</url-pattern>
  </servlet-mapping>
 
  <welcome-file-list>
    <welcome-file>redirect.html</welcome-file>
  </welcome-file-list>
 
</web-app>

JAR Files[edit]

Add the following JAR files to your application WEB-INF/lib:

  • click-1.x.jar
  • click-extras-1.x.jar

You can obtain these files from the Click distribution dist directory.

Welcome File[edit]

To ensure default application requests (e.g. http://localhost:8080/quickstart/) are sent to your applications home page we will add a redirect.html file to the web root directory. This file should contain:

<html>
<head><meta http-equiv="Refresh" content="0;URL=home.htm"></head>
</html>

This redirect.html file is configured in our web.xml, and any default requests will be served this file:

When the browser processes the redirect.html it will redirect to the applications home.htm page.

Home Page[edit]

Now we are ready to add our first Click page which will be our applications home page.

First we define a HomePage class, and ensure the class file is published to our web applications WEB-INF/classes directory:

package com.quickstart.page;
 
import net.sf.click.Page;
 
public class HomePage extends Page 
{
 
}

Next we add a corresponding Home page home.htm in the web root directory:

<html>
<head>
  <title>Home</title>
  <link rel="stylesheet" type="text/css" href="style.css" title="Style"/>
</head>
 
<body>
 
  <div id="header">
    <span id="title">Home</span>
  </div>
 
  <div id="container">
    <b>Welcome</b> to Home page your application starting point.
  </div>
 
</body>
</html>

Next add a style.css file to your web root directory:

 body {
 	font-family: Arial;
 	font-size: 11pt;
 	margin: 0;
 	padding: 0;
 }
 
 #header {
 	background: #FDE3B5 url(/click-quickstart/assets/banner.png) top left no-repeat;
 	border-bottom: 1px solid black;
 	height: 51px;
 	position: relative;
 	width: 100%;
 }
 
 #title {
 	color: white;
 	font-size: 24px;
 	font-weight: bolder;
 	position: absolute;
 	left: 15px;
 	top: 10px;
 }
 
 #container {
 	padding-top: 1em;
 	padding-left: 1.5em;
 	position: relative;
 	z-index: 0;
 }
 
 h3.title {
 	margin-top: 0em;
 	margin-bottom: 1em;
 }

You should now have the following web files:

Click application web files

Now, if your web application is deployed to the context path quickstart you should now be able to make the request:

http://localhost:8080/quickstart/

Your browser should be redirected to your HomePage and you should see your page rendered as:

Home

Welcome to Home page your application starting point.

In this example the Click automatically maps the home.htm request to our HomePage class and uses this class to process the request.

Border Template[edit]

Now we want to create a page border template so application pages will have a common look and feel.

First create a border-template.htm file in the web root directory. In this file include the HTML content:

<html>
<head>
<title>Click Quickstart - $title</title>
<link rel="stylesheet" type="text/css" href="$context/assets/style.css" title="Style"/>
</head>
 
<body>
 
  <div id="header">
    <span class="title">Quick Start :: $title</span>
  </div>
 
  <div id="container">
    #parse($path)
  </div>
 
</body>
</html>

Now we define a BorderPage class which specifies its template as the new border-template.htm file:

package com.quickstart.page;
 
import net.sf.click.Page;
 
public class BorderPage extends Page 
{
   public String getTemplate() 
   {
      return "border-template.htm";
   }
 
}

Note we named the template file border-template.htm so that it is not automatically mapped by Click to our BorderPage class.

Now we are going to modify our HomePage class to extend BorderPage and define a title value.

package com.quickstart.page;
 
public class HomePage extends BorderPage 
{
    public String title = "Home";
}

Next we modify our home.htm to remove the page border and only include the specific Home page content.

<b>Welcome</b> to Home page your application starting point.

You should now have the following web files:

Click application web files

Now if you make browser request to your updated home page you should see identical HTML content being rendered.

Home

Welcome to Home page your application starting point.

Logging[edit]

Click has some handy logging features which will show you how your page templates are being automatically mapped to you page classes. To enable debug logging add a mode value of "debug" to your click.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<click-app>
 
  <pages package="com.quickstart.page"/>
 
  <mode value="debug"/>
 
</click-app>

When the Click application starts up it will write out the following logging messages:

[Click] [debug] automapped pages:
[Click] [debug] /border-template.htm -> CLASS NOT FOUND
[Click] [debug] /home.htm -> com.quickstart.page.HomePage
[Click] [info ] initialized in debug mode

Click is telling us here that the border-template.htm template is not mapped to any Page class, while the home.htm template is mapped to our HomePage class. We are also informed that Click is running in debug mode.

When making a request to our home page we may get the following output:

[Click] [debug] GET http://localhost:8080/quickstart/home.htm
[Click] [info ] renderTemplate: /home.htm,border-template.htm - 46 ms
[Click] [info ] handleRequest:  /home.htm - 62 ms

This is telling us the HTTP request that the ClickServlet received. Then we can see that it is rendering the page path home.htm and template border-template.htm files in 46 milliseconds. Finally we can see that the total time to handle this request was 62 milliseconds

If you need more detailed debugging information change the application mode to trace. Now if we make the browser request:

http://localhost:8080/quickstart/home.htm?user=malcolm&password=secret

We will see the request parameters logged. This can be very handy for debugging form posts.

[Click] [debug] GET http://localhost:8080/quickstart/home.htm
[Click] [trace]    request param: password=secret
[Click] [trace]    request param: user=malcolm
[Click] [trace]    invoked: HomePage.<<init>>
[Click] [trace]    invoked: HomePage.onSecurityCheck() : true
[Click] [trace]    invoked: HomePage.onInit()
[Click] [trace]    invoked: HomePage.onGet()
[Click] [trace]    invoked: HomePage.onRender()
[Click] [info ]    renderTemplate: /user/home.htm,border-template.htm - 6 ms
[Click] [trace]    invoked: HomePage.onDestroy()
[Click] [info ] handleRequest:  /home.htm - 24 ms

What's Next[edit]

After you have the Quick Start application up and running you might be wondering, where do I go from here? There are lot of good code examples and patterns you can lift into your application:

  1. Add a Menu control to your border-template.htm to provide application wide navigation.
  2. Integrate J2EE Security into your application.

Use the Menu $menu.isUserInRoles() method in your menu rendering macro to only display a user's authorized menu options.