how does Spring know from the jsp what controller to use? - spring

Question

I have this in web.xml:
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<!-- Dispatching handled by StaticFilter -->
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
I have this in dispatcher-servlet.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.1.xsd">
<context:annotation-config/>
<!-- Activates scanning of #Repository -->
<context:component-scan base-package="com.pronto.mexp" />
<!-- View Resolver for JSPs -->
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="requestContextAttribute" value="rc"/>
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
<property name="prefix" value="/"/>
<property name="suffix" value=".jsp"/>
</bean>
</beans>
I have this in AlertsController:
#Controller
public class AlertsController {
protected final Log logger = LogFactory.getLog(getClass());
#Autowired
private AlertManager alertManager;
#RequestMapping("/alerts")
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// display in view
logger.info("Returning alerts view");
List<Alert> alerts = alertManager.getAlerts();
request.setAttribute("alerts", alerts);
return new ModelAndView();
}
public void setAlertManager(AlertManager alertManager) {
this.alertManager = alertManager;
}
}
And I have this in alerts.jsp:
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%# taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<h3>ALERTS</h3>
<table border="1">
<c:forEach var="alert" items="${alerts}">
<tr>
<td>${alert.hostname}</td>
<td>${alert.message}</td>
<td>${alert.program}</td>
<td><fmt:formatDate value="${alert.date}" dateStyle="medium"/></td>
</tr>
</c:forEach>
</table>
But when I start the app up and point my browser to localhost:8080/alerts.jsp, I get only the header "ALERTS" and nothing else. It's like Spring doesn't know to use the AlertsController. I know I'm leaving out some key config but I can't see it.

Answer 1

You're doing it opposite of what you're supposed to. It's not the JSP that knows which controller to use, but the Controller knows which view (JSP) to render. The controller is executed by it's url mapping, which is defined in the #RequestMapping attribute. When you access your JSP directly like that, you're not going through Spring at all. So try using the url http://localhost:8080/context/alerts instead, replacing context with the context path of the web application.

Answer 2

One line Answer : you are calling it in wrong way you have to call /alerts not alerts.jsp
but why you are getting this empty page, because you are calling jsp direct without setting values by controller, you are putting Jsp files under root
<property name="prefix" value="/"/>
so that it is accessible it is better to put it in WEB-INF to prevent direct access
<property name="prefix" value="/WEB-INF/jsps/"/>

Answer 3

My coworker pointed out my dispatcher-servlet.xml was also missing the mvc instruction to scan for annotations in my Controllers:
<!-- Configures the #Controller programming model -->
<mvc:annotation-driven/>
So even when I pointed my browser at localhost:8080/alerts (since I have no context path configured), it was still failing. Once I added the mvc instruction, the controller was invoked, and the dynamic content was sent to the jsp.