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Different Ways of Defining Components in Java Drawer UPC-A Supplement 2 in Java Different Ways of Defining Components

3. use j2ee upc code writer togenerate upc a in java Oracle Reports Let"s see what has h jdk UPC Code appened here. In the code of the Start page, we have used an injected instance of the Another page to set a message on it. Then we asked Tapestry to show the Another page which, as we"ve seen before, would normally mean wiping out the message (perhaps by sending the instance we have just used back to the pool) and displaying a fresh empty instance of the Another page, perhaps just taken from the pool.

However, before sending the first instance back to the pool, Tapestry will check whether the Another page uses the activation context by implementing the pair of methods, onActivate and onPassivate. As it does, Tapestry will invoke the onPassivate method of that instance, which is like asking "Hey, instance of the Another page, is there anything you want me to pass to another instance of your page that will continue your work ". You can see from the code that the onPassivate method will report the contents of the message we have just set, and Tapestry will remember its answer.

As soon as it uses another instance of the Another page, it will pass the stored message as a parameter to the onActivate method of the new instance, and this way we shall be able to see the message properly displayed on the page. But how will Tapestry remember the message if it does not create a session Have a look at the URL used to display the Another page:. http://localhost:808 0/t5first/another/hi+there%21. The message was reco j2ee UPC Code rded into the URL while redirecting the user"s browser to the Another page, and so Tapestry was able to restore the message without ever creating a session. This also means that the Another page can now be bookmarked, and it will show you the message successfully, even if you come to read it after a few months! Now imagine that this page was used to display a product from an online catalog, and you will appreciate the benefits of using the activation context. This was another way of passing information from one page to another.

Now let"s return to how we define components on the pages there are a few different ways to do that too.. Different Ways of Defining Components <t:textfield t:value="message"/> So far, we have seen just one approach to defining a component on a page by using an XML element in the Tapestry namespace, like this:. [ 67 ]. The Foundations of Tapestry However, this simple javabean UPC-A approach has a downside. If we preview the Start page template in a web browser, we"ll see something similar to this:. It is not a problem that the values to be inserted into the page are replaced by expansions. This is a static preview, after all. What is worse, some components have simply disappeared.

We do not see the link to the Another page, and there is no text box. This means that when we are declaring components as shown above, we are losing the ability to preview the page template in a web browser and to continue editing it using common HTML editors like Dreamweaver. This might not be a big deal if you are creating both templates and page classes on your own and if the design of the page is not too complicated.

However, web applications are often developed by a mixed team where designers work on templates while developers concentrate on page classes. Also, it is often easier to start developing a page from its HTML mock up, discussed and agreed upon with the customer. In these cases, Tapestry"s ability to make its instrumentation invisible becomes very important.

Change the TextField declaration to look like this:.
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