On 3/9/06, Tom Ziemer <[EMAIL PROTECTED]> wrote: > > Hi Craig, > > sorry, if this is totally OT, but I just posted a similar question in > the sun forum: Where would you actually place the code you mentioned > within a JSF component? I mean beginEncode() is called each time the > page is requested so what can I do, if I only want to add a component > once? I don't think that implementing NamingContainer and calling > findComponent() is a really nice solution ...
I can point you at a real example, if you prefer :-). You know how most databases come with some sort of client application that lets you type in SELECT statements and then dynamically creates a table (based on the column names returned by the query) to display the responses? I've got just such an example app (shale-sql-browser) in the Shale nightly builds[1]. Drop the war file onto your favorite servlet container, and type "select * from zip_codes" into the query field and submit the form. Although this particular example uses Shale's "prerender()" callback method, it is still easy to understand when you'd do this in terms of the standard JSF lifecycle: * RESTORE VIEW - JSF sees the incoming request and restores the previous component tree * APPLY REQUEST VALUES - JSF updates the local values of any input components, based on the request parameters. In this case, it notices the values of the "query" parameter, which will contain the SELECT statement to execute. * PROCESS VALIDATIONS - JSF checks any validations. None in this example. * UPDATE MODEL VALUES - JSF pushes values into the model. In this case, it pushes the local value of the "query" parameter into the "query" property of the backing bean (Query.java). * INVOKE APPLICATION - Grab the query string and actually execute it, creating a ResultSet. Find the table component, and clear its old children. Grab the ResultSetMetaData for the result set. Dynamically construct child components for all of the database columns that were returned. * RENDER RESPONSE - Display the resulting component tree, which was partially created from the JSP page (it has an empty <h:table> component for the response data) and partially created by dynamic component creation. So, you'd typically operate on the input data during the action method that is called when the form is submitted, setting up the data to be used later. If you are going to redisplay the same page, you can also do the component creation at that point in time -- if you're navigating to a different page, you will need a phase listener listening for a "before render response" event, because you need the second page's component tree to have been created already. If you're doing that, though, just go ahead and use Shale and stick the component creation into the prerender() method. That way you won't have to worry about what the heck a "phase listener" is. Thanks, > Tom Craig [1] http://cvs.apache.org/builds/struts/nightly/struts-shale/ Craig McClanahan wrote: > > On 3/9/06, Rivka Shisman <[EMAIL PROTECTED]> wrote: > >> Hi friends, > >> > >> > >> > >> I need to dynamically build an input form that may contain various > >> html:fields (i.e. html:text, html:select, html:radio etc). > >> > >> The type and name of the html:field will be determined at runtime (from > >> DB table). > >> > >> How can I do it using Struts and JSP? > > > > > > Basically, you can not do this sort of thing with the Struts HTML tags > ... > > but you could easily do it with JavaServer Faces components. A quick > > snapshot to give you the idea of how it works: > > > > HtmlForm form = ...; // Acquire a reference to the parent form > component > > > > HtmlOutputLabel label1 = new HtmlOutputLabel(); // Label for > username > > field > > label1.setValue("Username:"); > > > > HtmlInputText username = new HtmlInputText(); // Username field > > username.setId("username"); > > > > HtmlOutputLabel label2 = new HtmlOutputLabel(); // Label for > password > > field > > label2.setValue("Password:"); > > > > HtmlInputSecret password = new HtmlInputSecret(); // Password field > > password.setId("password"); > > > > HtmlCommandButton submit = new HtmlCommandButton(); // Submit button > > submit.setId("logon"); > > > > List children = form.getChildren(); > > children.add(label1); > > children.add(username); > > children.add(label2); > > children.add(password); > > children.add(submit); > > > > There's lots more you can do, but this gives the basic flavor of > dynamically > > creating component hierarchies. > > > > Thanks > >> Rivka > > > > > > Craig > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > >
