A typical request handler in Spring MVC is based on the @Controller and @RequestMapping annotations. Create a Java class, org.jboss.springmvc.controller.CatalogController, annotated with the @Controller annotation, which makes the class auto-detectable for injection by Spring. In the springmvcsrcmainwebappWEB-INFjboss-as-spring-mvc-context.xml context file, which is listed and discussed later in the chapter, the component scanning for the org.jboss.springmvc.mvc base package is configured, as follows:

<context:component-scan base-package="org.jboss.springmvc.controller" />

BeanFactory injects a catalogController bean when the CatalogController class is required to handle a request. The handler class creates a model Map with data and selects a view name to be rendered. The createAndDisplayCatalog method takes the servlet request sent by DispatcherServlet and returns an org.springframework.web.servlet.ModelAndView object, which is a holder for Model and View in the Spring MVC framework. Map the servlet request onto the createAndDisplayCatalog handler method using the @RequestMapping annotation. Specify the path mapping URI as /catalog.

Autowire the org.jboss.springmvc.data.CatalogDao DAO interface to Spring's dependency injection mechanism using the @AutoWire annotation. A catalogDaoImpl bean is injected on startup as, by default, the application context pre-instantiates all singleton (the default scope in Spring) beans at startup. The createAndDisplayCatalog method gets the request parameter values and creates a Catalog object. The Catalog object is stored using the autowired DAO object's persist method. Having created a model Map, the createAndDisplayCatalog method returns a org.springframework.web.servlet.ModelAndView object with the View catalog and the catalogDao model. The org.springframework.web.servlet.ModelAndView object is returned to DispatcherServlet for the servlet to render the response. The view ID is resolved using the view resolver specified in the jboss-as-spring-mvc-context.xml context file. The Map model is made available to the view template. The controller class is listed in the following code:

package org.jboss.springmvc.controller;

import org.jboss.springmvc.data.*;
import org.jboss.springmvc.model.*;
import javax.servlet.http.HttpServletRequest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class CatalogController {
  @Autowired
  private CatalogDao catalogDao;
  
  @RequestMapping(value = "/catalog")
  public ModelAndView createAndDisplayCatalog(HttpServletRequest request) {
    // Handle a new catalog (if any):
    String journal = request.getParameter("journal");
    String publisher = request.getParameter("publisher");
    String edition = request.getParameter("edition");
    String title = request.getParameter("title");
    String author = request.getParameter("author");
    if (journal != null && publisher != null && edition != null
    && title != null && author != null) {
      Catalog catalog = new Catalog();
      catalog.setJournal(journal);
      catalog.setPublisher(publisher);
      catalog.setEdition(edition);
      catalog.setTitle(title);
      catalog.setAuthor(author);
      catalogDao.persist(catalog);
    }
    // Prepare the result view (catalog):
    return new ModelAndView("catalog", "catalogDao", catalogDao);
  }
}

The model, DAO, and controller classes are shown in Project Explorer in the following screenshot: