Section 5.10. Editing a Car | JBoss at Work: A Practical Guide

5.10. Editing a Car

To edit an existing car, we'll add another set of links on the viewCarList page in Figure 5-4.

Figure 5-4. Editing cars

The Edit links each contain the ID of the displayed car. They call the ControllerServlet using the editCar action. Example 5-21 shows the JSP code.

Example 5-21. carList.jsp

 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <html> <head>   <link rel="stylesheet" type="text/css" href="default.css"> </head> <body>   <p><a href="controller?action=addCar">[Add Car]</a></p>   <table>       <tr>           <th>Action</th>           <th>Make</th>           <th>Model</th>           <th >Model Year</th>       </tr>       <c:forEach items='${carList}' var='car'>       <tr>           <td><a href="controller?action=editCar&id=${car.id}">Edit</a></td>           <td>${car.make}</td>           <td>${car.model}</td>           <td >${car.modelYear}</td>       </tr>       </c:forEach>   </table> </body> </html>

The ControllerServlet in Example 5-22 catches the request, queries the requested CarDTO out of the database using the ID, places it in the Request scope, and finally redirects to the carForm.jsp.

Example 5-22. ControllerServlet.java

 // perform action         if(VIEW_CAR_LIST_ACTION.equals(actionName))         {             CarDAO carDAO = new HibernateCarDAO(  );             request.setAttribute("carList", carDAO.findAll(  ));             destinationPage = "/carList.jsp";         }         else if(ADD_CAR_ACTION.equals(actionName))         {             request.setAttribute("car", new CarDTO(  ));             destinationPage = "/carForm.jsp";         }         else if(EDIT_CAR_ACTION.equals(actionName))         {             int id = Integer.parseInt(request.getParameter("id"));             CarDAO carDAO = new HibernateCarDAO(  );             request.setAttribute("car", carDAO.findById(id));             destinationPage = "/carForm.jsp";         }         else if(SAVE_CAR_ACTION.equals(actionName))         {             //build the car from the request parameters             CarDTO car = new CarDTO(  );             car.setMake(request.getParameter("make"));             car.setModel(request.getParameter("model"));             car.setModelYear(request.getParameter("modelYear"));             //save the car             CarDAO carDAO = new HibernateCarDAO(  );             carDAO.create(car);             //prepare the list             request.setAttribute("carList", carDAO.findAll(  ));             destinationPage = "/carList.jsp";         }         else         {             String errorMessage = "[" + actionName + "] is not a valid action.";             request.setAttribute(ERROR_KEY, errorMessage);         }

This time having a filled-in CarDTO in Request scope allows us to populate the form in Figure 5-5 with the appropriate data.

Figure 5-5. carForm.jsp used to edit a CarDTO

The "Save" button still sends the form data back to the ControllerServlet using the saveCar action, only this time the ID value is a positive integer. (Recall that CarDTO.id is initialized to "-1" unless you provide a specific value.) This allows us to reuse the saveCar method for both inserts and updates. Example 5-23 shows the modified method in ControllerServlet.

Example 5-23. ControllerServlet.java

 // perform action         if(VIEW_CAR_LIST_ACTION.equals(actionName))         {             CarDAO carDAO = new HibernateCarDAO(  );             request.setAttribute("carList", carDAO.findAll(  ));             destinationPage = "/carList.jsp";         }         else if(ADD_CAR_ACTION.equals(actionName))         {             request.setAttribute("car", new CarDTO(  ));             destinationPage = "/carForm.jsp";         }         else if(EDIT_CAR_ACTION.equals(actionName))         {             int id = Integer.parseInt(request.getParameter("id"));             CarDAO carDAO = new HibernateCarDAO(  );             request.setAttribute("car", carDAO.findById(id));             destinationPage = "/carForm.jsp";         }         else if(SAVE_CAR_ACTION.equals(actionName))         {             //build the car from the request parameters             CarDTO car = new CarDTO(  );             car.setId(Integer.parseInt(request.getParameter("id")));             car.setMake(request.getParameter("make"));             car.setModel(request.getParameter("model"));             car.setModelYear(request.getParameter("modelYear"));             //save the car             CarDAO carDAO = new HibernateCarDAO(  );             if(car.getId(  ) =  = -1)             {                 carDAO.create(car);             }             else             {                 carDAO.update(car);             }             //prepare the list             request.setAttribute("carList", carDAO.findAll(  ));             destinationPage = "/carList.jsp";         }         else         {             String errorMessage = "[" + actionName + "] is not a valid action.";             request.setAttribute(ERROR_KEY, errorMessage);         }

Which, of course, brings us back to the DAO. Example 5-24 shows what the update code looks like in JDBCCarDAO.

Example 5-24. JDBCCarDAO.java

 public void update(CarDTO car)     {         DataSource dataSource = null;         Connection conn = null;         PreparedStatement pstmt = null;         String insertSql =                "update CAR set MAKE=?, MODEL=?, MODEL_YEAR=? where id=?";         try         {             dataSource = ServiceLocator.getDataSource(DATA_SOURCE);             conn = dataSource.getConnection(  );             pstmt = conn.prepareStatement(insertSql);             pstmt.setString(1, car.getMake(  ));             pstmt.setString(2, car.getModel(  ));             pstmt.setString(3, car.getModelYear(  ));             pstmt.setInt(4, car.getId(  ));             pstmt.executeUpdate(  );         }         catch (Exception e)         {             System.out.println(e);         }         finally         {             try             {                 if(pstmt != null){pstmt.close(  );}                 if(conn != null){conn.close(  );}             }             catch(Exception e)             {                 System.out.println(e);             }         }     }

And Example 5-25 shows the corresponding reduced code in HibernateCarDAO.

Example 5-25. HibernateCarDAO.java

     public void update(CarDTO car)     {         Session session = null;         Transaction tx = null;         try         {             session =               ServiceLocator.getHibernateSession(HIBERNATE_SESSION_FACTORY);             tx = session.beginTransaction(  );             session.update(car);             tx.commit(  );         }         catch (Exception e)         {             try{tx.rollback(  );}             catch(Exception e2){System.out.println(e2);}             System.out.println(e);         }         finally         {             try             {                 if (session != null) {session.close(  );}             }             catch (Exception e)             {                 System.out.println(e);             }         }     }

Type ant in the root directory of 05c-edit to build the project.
Shut down JBoss.
Type ant colddeploy.
Start JBoss back up.
Visit http://localhost:8080/jaw in a web browser.

Use the web interface to make changes to the cars in the database.