Multiple submits
On the detail page (detail.jsp) there are 4 different actions,
all implemented through submit-buttons. This
leaves us with a problem since only one action is specified
in the <html:form> tag. In order for us to
distinguish the 4 actions from each other I've added an onclick
event to each button, for example:
onclick="go('update')"
where "go" is a JavaScript function that inserts the parameter in
a hidden form field called "action":
function go(action) {
document.forms[0].action.value=action;
}
The action used on the detail page is called "process" and its
Action class simply acts as a relay to the
proper command:
// extract the value of the hidden "action" field
return (mapping.findForward(request.getParameter("action")));
Since there are 4 possible action-values we must also define 4
forwards for the "process" action in the
struts-config.xml file.
The struts-config.xml file
The global-forwards section
This section, which I did not mention in my first article, is
used to define the "forwards" that are
global to the application. Obvious candidates are of course
"system error"-pages, which may be used by
many actions, but in the DVD application I've also defined global
forwards to the Detail and the List pages.
These should only be used where there's no doubt about how the
flow from one page to another should be.
The "list" action is an example. It must go to the List page.
<global-forwards>
<forward name="error" path="/error.jsp"/>
<forward name="list" path="/list.jsp"/>
<forward name="detail" path="/detail.jsp"/>
</global-forwards> |
The form-beans section
This section only contains the DetailForm class:
<form-beans>
<form-bean name="detailForm"
type="hansen.playground.DetailForm"/>
</form-beans> |
The action-mappings section
This section contains the 7 actions--plus the "process" action.
Click
here
to display the section in a separate window.
<action-mappings>
<action path="/list"
type="hansen.playground.ListDVDAction"
parameter="d:\\dvds.xml">
</action>
<action path="/detail"
type="hansen.playground.DetailDVDAction"
name="detailForm"
validate="false"
scope="request">
</action>
<action path="/save"
type="hansen.playground.SaveDVDAction">
</action>
<action path="/process"
type="hansen.playground.ProcessDVDAction"
name="detailForm"
scope="request"
validate="false">
<forward name="create" path="/create.do"/>
<forward name="update" path="/update.do"/>
<forward name="delete" path="/delete.do"/>
<forward name="cancel" path="/cancel.do"/>
</action>
<action path="/create"
type="hansen.playground.CreateDVDAction"
name="detailForm"
input="/detail.jsp"
scope="request">
<forward name="OK" path="/detail.jsp"/>
</action>
<action path="/update"
type="hansen.playground.UpdateDVDAction"
name="detailForm"
input="/detail.jsp"
scope="request">
<forward name="OK" path="/detail.jsp"/>
</action>
<action path="/delete"
type="hansen.playground.DeleteDVDAction"
name="detailForm"
scope="request"
validate="false">
<forward name="OK" path="/list.jsp"/>
</action>
<action path="/cancel"
forward="/list.jsp">
</action> |
Some comments to these definitions:
|
action |
comments |
|
list |
The "parameter" keyword can be used to transfer data to the Action
class. In this example we give the name
of the xml file to read.
The Action class may retrieve the value like this:
String filename = mapping.getParameter();
|
|
detail |
The "DetailDVDAction" class fills data in the "DetailForm"
instance for detail.jsp to display.
The detail command is given as a hyperlink:
<a href="detail.do?index=<%=i%>">
An "index" member variable is therefore added to the
"DetailForm" class.
The hyperlink acts precisely as a form submit with method=get.
|
|
save |
Is implemented without a submit. A button with an onclick event
is used to invoke the save action. |
|
process |
Since the process action is defined in an HTML form we need an
ActionForm. The ProcessDVDAction does not use
it however. |
|
create and update |
"validate" defaults to "true". Note that by defining the "forward"
with the action we can change the target
page without having to recompile the Action class. |
|
cancel |
Since "cancel" only directs the browser to the List page we use
"forward" instead of "type" to avoid defining
an Action class. |
Here's
the complete struts-config.xml file.
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