Click can support multiple pages elements to enable the automapping of multiple packages.

<click-app>

  <pages package="com.mycorp.banking.page"/>

  <pages package="com.mycorp.common.page"/>

</click-app>

With multiple pages elements, pages are loaded in the order of the page elements, with manual page elements being loaded before automapped pages. Once a page template has been mapped to a Page class it will not be replaced by a subsequent potential match. So pages elements at the top take priority over lower pages elements.

Page automapping will automatically configure application pages using a simple set of rules. This enables you to greatly streamline your configuration file as you only need to define pages which don't fit the automapping rules.

Automapping will attempt to associate each page template (*.htm) and JSP file in the web application (excluding those under WEB-INF) to a Page class. Automapped pages are loaded after the manually defined pages are loaded, and manually defined pages takes preference. When automapping is enabled the page mappings will be logged if Click is running in debug or trace mode.

For example, given the following page path to class mapping:

The above mapping could be configured manually by setting the automapping attribute to false, for example:

<click-app>
  <pages automapping="false">
    <page path="index.htm"                    classname="com.mycorp.page.Home"/>
    <page path="search.htm"                   classname="com.mycorp.page.Search"/>
    <page path="contacts/contacts.htm"        classname="com.mycorp.page.contacts.Contacts"/>
    <page path="security/login.htm"           classname="com.mycorp.page.security.Login"/>
    <page path="security/logout.htm"          classname="com.mycorp.page.security.Logout"/>
    <page path="security/change-password.htm" classname="com.mycorp.page.security.ChangePassword"/>
  </pages>
</click-app>

For an application with many pages, it is cumbersome to manually map each page template to its associated class. This is where automapping comes in.

By setting automapping to true, Click will automatically map page templates to page classes. To map a template to a page class, Click converts the template path to the Page classname. In the example above, Click will convert the template search.htm to the class Search by capitilizing the template name and removing the .htm extension. Of course this is not enough to map the template to the class. what is missing is the class package, com.mycorp.page. To help Click map the page, you can set the base package attribute as shown in the next example.

Below is the full configuration to automatically map the templates to pages (except for index.htm which doesn't automatically map to Home page and has to be mapped manually):

<click-app>
  <pages package="com.mycorp.page" automapping="true">
    <page path="index.htm" classname="com.mycorp.page.Home"/>
  </pages>
</click-app>

Note: automapping is true by default, so it could be omitted.

If a page template is placed in a sub folder of the root web folder, it's associated page class must be placed in an equivalently named sub package of the base package in order for the page to be mapped automatically. In the mapping above the page template security/change-password.htm is located in the security folder under the web root. In order for Click to correctly map the page template to it's class, the class must be located in the security package of the base package com.mycorp.page. The absolute page classname is thus: com.mycorp.page.security.ChangePassword.

The page template name to classname convention is:

During automapping, if a page class cannot be found, Click will add the 'Page' suffix to the classname (if not already present) and attempt to map the page template to this modified classname. For example:

With Page automapping there can be resources where you don't want automapping applied. For example when using a JavaScript library with lots of .htm files, you don't want automapping to try and find Page class for each of these files. In these situations you can use the pages excludes element.

For example if our application uses the TinyMCE JavaScript library we could configure our pages automapping to exclude all .htm files under the /tiny_mce directory.

<click-app>
  <pages package="com.mycorp.page">
    <excludes pattern="/tiny_mce/*"/>
  </pages>
</click-app>

The excludes pattern can specify multiple directories or files using a comma separated notation. For example:

<click-app>
  <pages package="com.mycorp.page">
    <excludes pattern="/dhtml/*, /tiny_mce/*, banner.htm, about.htm"/>
  </pages>
</click-app>

HTM files excluded from Page automapping are handled by an internal Page class with caching headers enabled.

Autobinding is a feature that allows certain page variables to be handled in a special way by the ClickServlet. The autobinding attribute can be configured with one of the following values:

By default all pages have autobinding enabled in default mode.

Please note: we recommend using autobinding only for binding request parameters, not for Controls. It generally leads to code that is difficult to maintain. In a future release we will replace autobinding with a simpler implementation.

With autobinding the ClickServlet will automatically:

For example:

public class EmployeePage extends Page {

    public String employeeDescription;

    // Form does not have a name defined
    public Form employeeForm = new Form();

    // Table defines its own name
    public Table employeeTable = new Table("table");

}

Note in the example above that the employeeDescription variable and the employeeForm and employeeTable controls are not added to the page. Also note that Form name is not defined.

When autobinding is enabled, ClickServlet will create a new Page and add the bindable variables and controls to the page. Following the example above the employeeDescription, employeeForm and employeeTable will be added to the page, which is equivalent to the following statements: addModel("employeeDescription", employeeDescription), addControl(employeeForm) and addControl(employeeTable).

Furthermore, controls that do not have a name defined will have their name set to their instance variable name. In this case the Form name will be set to employeeForm while the Table name won't be altered since it already has a name defined.

The above example is a shorthand way of writing the following:

public class EmployeePage extends Page {

    private String employeeDescription;

    private Form employeeForm = new Form();

    private Table employeeTable = new Table("table");

    public void onInit() {
        employeeForm.setName("employeeForm");
        addControl(employeeForm);

        addControl(myTable);
    }
}

Note that we did not show where employeeDescription is added to the page model. The reason for that is because autobinding handles non controls slightly differently. Non control variables are added to the model just before the page response is written. This allows the value of the variable to be set anywhere in the page. For example:

public class EmployeePage extends Page {

    private String employeeDescription;

    private Form employeeForm = new Form();

    private Table employeeTable = new Table("table");

    ...

    public boolean onSaveClick {
        if (employeeForm.isValid()) {
            // employeeDescription is added to the page model just before the
            // response is written
            employeeDescription = employee.getDescription();
        }
    }
} 

employeeDescription will be added to the page model and can be referenced in the page template as $employeeDescription.

Autobinding can be turned off by setting the autobinding attribute to none as shown below:

<click-app>
  <pages package="com.mycorp.page" autobinding="none"/>
</click-app>

Click provides the Bindable annotation which enables autobinding of Page variables The Bindable annotation can bind private, protected and public Page variables.

By default, Click's autobinding feature operates on both public and @Bindable variables. To instruct Click to operate only on @Bindable annotated variables, you can set the autobinding attribute to annotation, for example:

<click-app>
  <pages package="com.mycorp.page" autobinding="annotation"/>
</click-app>

Click won't autobind public variables anymore.

Below is an example using the @Bindable annotation:

public class EmployeePage extends Page {

    @Bindable protected Form employeeForm = new Form();

    @Bindable protected Table myTable = new Table();

}

Headers are typically used to switch off browser caching. By default Click will use the following no caching header values if you don't define a headers element in your application:

<click-app>
  <pages>
     ..
  </pages>
  <headers>
    <header name="Pragma" value="no-cache"/>
    <header name="Cache-Control"
            value="no-store, no-cache, must-revalidate, post-check=0, pre-check=0"/>
    <header name="Expires" value="1" type="Date"/>
  </headers>
</click-app>

Alternatively you can define your headers individually in pages or for all application pages by setting header values. For example, to switch off caching in the Login page, set the following page cache control headers:

<pages package="com.mycorp.page">
  <page path="login.htm" classname="com.mycorp.page.Login">
    <header name="Pragma" value="no-cache"/>
    <header name="Expires" value="1" type="Date"/>
  </page>
</pages>

Note: the value for a Date type should be a long number value.

If you wanted to enable caching for a particular page you could set the following page cache control header. This will mark the page as cachable for a period of 1 hour after which it should be reloaded.

<pages package="com.mycorp.page">
  <page path="home.htm" classname="com.mycorp.page.Home">
    <header name="Cache-Control" value="max-age=3600, public, must-revalidate"/>
  </page>
</pages>

To apply header values globally define header values in the headers element. For example:

<click-app>
  <pages>
     ..
  </pages>
  <headers>
    <header name="Pragma" value="no-cache"/>
    <header name="Cache-Control"
               value="no-store, no-cache, must-revalidate, post-check=0, pre-check=0"/>
    <header name="Expires" value="1" type="Date"/>
  </headers>
</click-app>

When Page Auto Loading is enabled any new page templates and classes will be automatically loaded at runtime. These pages are loaded using the Page Automapping rules.

Page auto loading is a very handy feature for rapid development as you do not have to restart you application server to pick up new pages.

The Click and Velocity runtimes use LogService for logging messages. The default LogService implementation is ConsoleLogService which will send messages to the console [System.out]. For example the following logging output is for a HomePage request when the application mode is trace:

Any unhandled Throwable errors are logged by the ClickServlet.

Note that Click Extras also provide log adaptors for Log4J and the JDK Logging API.

When an application is not in production mode the error page displays detailed debugging information. When the application mode is production no debug information is displayed to prevent sensitive information being revealed. This behaviour can be changed by modifying the deployed click/error.htm page template.