Quick question about Spring/Struts Controller comparison

[crazeinc]

In Struts if you want to have mulitple return views in Struts, you just add more lines to your struts-config.xml for instance:
<forward name="success" path="/WEB-INF/results/result1.jsp"/>
<forward name="baddata" path="/WEB-INF/results/result2.jsp"/>

But in the Spring examples I've seen, I've only seen a success view written in the action-servlet.xml like:
<property name="successView"><value>index.jsp</value></property>

Is there a way to specify the "error" views in Spring the xml without having to hard-code them in the Controller class?

Thanks,
PJ

[mraible]

You could add an errorView property to your controller and associated get/setErrorView methods. Then add this as a property in your context XML file.

HTH,

Matt

[crazeinc]

Matt you're everywhere, this is the same guy that asked you about the ldap stuff this past weekend I have it implemented using a LdapDAO, but it's not quite as slick as I'd like it to be just yet. I'll probably post a thread about it later this evening in the Architecture Discussion forum here if you're curious. Thanks for the response BTW.

-PJ

[jpwinans]

Hey PJ,

I'm just becoming familiar with Spring myself, but here is what I've learned from my first app...
There are a couple of things you can do. First, you can define an ExceptionResolver in your servlet context file:

<bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
		<property name="exceptionMappings">
			<props>
				<prop key="org.springframework.dao.DataAccessException">dataAccessFailure</prop>
				<prop key="org.springframework.transaction.TransactionException">dataAccessFailure</prop>
			</props>
		</property>
</bean>

Then, depending on how you set up your ViewResolver, you just set the URL of the dataAccessFailure view. If you're using ResourceBundleViewResolver, your views.properties file would contain something like the following:

dataAccessFailure.class=org.springframework.web.servlet.view.JstlView
dataAccessFailure.url=/WEB-INF/jsp/dataAccessFailure.jsp

Using this method, you can "catch" any RuntimeException and "throw" it to a specific view, jsp page in this case.

As a second point, if the "baddata" you are refering to is the failure to pass a validator, then the same view will be redisplayed. If you've bound in any error messages, they would then appear. Here is an example using jsp. It is a simple form field expecting an IP address:

<B>IP Address&#58;</B>
<spring&#58;bind path="command.ip">
  <FONT color="red">
    <B><c&#58;out value="$&#123;status.errorMessage&#125;"/></B>
  </FONT>
  <INPUT type="text" maxlength="30" size="30" name="ip" value="<c&#58;out value="$&#123;status.value&#125;"/>" >
</spring&#58;bind>
<P>

If on validation, the controller throws a validation error, this jsp will display that error message.

The other thing I've seen is to have your controller handle specific data by returning a Redirection view...

public ModelAndView computerHandler(HttpServletRequest request, HttpServletResponse response) throws ServletException {
   		Computer computer = getApplicationFacade()
               .loadComputer(RequestUtils.getIntParameter(request, "computerId", 0));
   		if (computer == null) {
   			return new ModelAndView("findComputersRedirect");
   		}
   		Map model = new HashMap();
   		model.put("computer", computer);
   		return new ModelAndView("computerView", "model", model);
 }

In this case, the controller looks for a QueryString called computerId, and uses it to look up a computer in the database. If it doesn't return a computer, the controller then redirects it to the view called "findComputersRedirect".

Like I said, I'm by no means an expert at Spring yet, but I hope this helps you a bit.

Take care,
James

[crazeinc]

All very helpful, thanks James. One question I did have, though, concerning your "findComputersRedirect" view. Would you specify that in action-servlet.xml with something along these lines?

<property name="findComputersRedirect"><value>foo.jsp</value></property>

[jpwinans]

Hey,

"findComputersRedirect" is actually a view name that is defined, in this case, within the views.properties file:

findComputersRedirect.class=org.springframework.web.servlet.view.RedirectView
findComputersRedirect.url=findComputers.htm

The reason is to resend, in this case, http://host/appName/findComputers.htm which is then re-handled by the servlet's mappings. It is in the servlet's mappings that findComputers.htm is handed over to the corresponding controller bean:

<bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
		<property name="mappings">
			<props>
				<prop key="/findComputers.htm">findComputersForm</prop>
			</props>
		</property>
	</bean

<bean id="findComputersForm" class = "application.web.spring.FindComputersForm">
		<property name="formView"><value>findComputersForm</value></property>
		<property name="selectView"><value>selectComputerView</value></property>
		<property name="successView"><value>computerRedirect</value></property>
</bean>

-James