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Creating Custom Components in Java Encode UCC - 12 in Java Creating Custom Components




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Creating Custom Components generate, create none none in none projects Code 128 Code Set C This is already c none for none loser to a real life application, but all those "quick and dirty" links that connect pages to each other are not a proper means for navigation. We need a navigation menu..

Adding a Navigation Menu Let me admit from none none the very beginning that I am not going to show a production quality menu. That would require a serious use of styles, and I don"t want to create such a distraction for you. We are going to use a simple table for layout, and a set of links.

This will provide a decent foundation, and you can add any kind of styling to it when you have time. All work will concentrate on the Border component template. Here is what we want to see when the application is rendered on the AddCelebrity page:.

[ 200 ]. 8 . And here are the additions to the Border.tml template that we need to make to achieve this:. <html xmlns:t= none for none "http://tapestry.apache.org/schema/tapestry_5_0_0.

xsd"> <head> <title>Celebrity Collector</title> <link rel="stylesheet" href="${asset:context:/assets/styles.css}" type="text/css"/> </head> <body> <p align="right"> <img src="${asset:context:/assets/flag.gif}" align="middle"/> <t:actionlinkt:id="switchlocale"> ${localeLabel} </t:actionlink> </p> <table width="100%"> <tr> <td width="100" valign="top"> <br/> <br/> <br/> <t:pagelink t:page="Start">Home</t:pagelink><br/> <t:pagelink t:page="Registration"> Registration</t:pagelink><br/> <t:pagelink t:page="ShowAll"> All Celebrities</t:pagelink><br/> <t:pagelink t:page="AddCelebrity"> Add New</t:pagelink> </td> <td> <t:body/> </td> </tr> </table> </body> </html>.

[ 201 ]. Creating Custom Components Now we can easily navigate from page to page, although we shall not be able to see the ShowAll page until we log in properly. This navigation menu however, is far from being perfect. There are at least two enhancements that we might want to add: 1.

There is no need to display the navigation menu on the Start page, at least until the user hasn"t logged in. 2. There is no need to link a page to itself, for example when we are at the ShowAll page, the All Celebrities link could be disabled.

For any of these tasks, the Border component will need to know which page renders it at that moment. We can easily find the class name of the page that contains the component using the already familiar ComponentResources class, like this:. @Inject private C none for none omponentResources resources; private String getPageName() { Component page = resources.getContainer(); return page.getClass().

getName(); }. We can also provi de a few simple methods that will check if the current page is the Start page, the Registration and so on as many methods as there are links in the navigation menu:. public boolean is none for none NotStart() { return !getPageName().equals(Start.class.

getName()); } public boolean isRegistration() { return getPageName().equals(Registration.class.

getName()); } public boolean isShowAll() { return getPageName().equals(ShowAll.class.

getName()); } public boolean isAddCelebrity() { return getPageName().equals(AddCelebrity.class.

getName()); }. [ 202 ]. 8 . Finally, we can s urround the links with an If component that will hide the menu when the displayed page is the Start page, and add a disabled parameter to the PageLink components:. <t:if t:test=" none for none notStart"> <t:pagelink t:page="Start"> Home</t:pagelink><br/> <t:pagelink t:page="Registration" t:disabled="registration"> Registration</t:pagelink><br/> <t:pagelink t:page="ShowAll" t:disabled="showAll"> All Celebrities</t:pagelink><br/> <t:pagelink t:page="AddCelebrity" t:disabled="addCelebrity"> Add New</t:pagelink> </t:if>. When a PageLink"s disabled parameter is set to true, the text surrounded by the component will be rendered, but there will be no link associated with it exactly as we wanted. Run the application and make sure that it works properly. There is still one problem about the Border component however.

The browser title bar displays the same title Celebrity Collector for all the pages. This might not be a big deal for human users, but search engines expect each page of a web application to have a unique title, corresponding to the page"s content, and we need to ensure that..

Using a Parameter The most natural solution for displaying a page-specific title is to pass this title to the Border component as a parameter, and this is very easy to do. First of all, let"s prepare the component"s template to display the title:. <head> < none none title>Celebrity Collector: ${pageTitle}</title> title>Celebrity <link rel="stylesheet" href="${asset:context:/assets/styles.css}" type="text/css"/> </head> . [ 203 ].
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