注解驱动的spring mvc(二)

四：视图名的确定。

spring mvc可以通过可以通过多种方式确定视图名，在前面的例子中，方法无返回值，视图名更具请求参数确定。Controller方法还是返回一个String类型的值作为视图名。

@RequestMapping("/user/list.htm")
public String listAllUser(){
    return "user/list-user";
}

@RequestMapping("/user/list.htm")
public String listAllUser(){
	return "user/list-user";
}

那么该例子的视图文件就为/WEB-INF/jsp/user/list-user.jsp

五：视图模型参数的传递。

在spring mvc中可以通过ModelMap对象传递模型参数到视图进行处理。在Controller方法中声明一个ModelMap参数，spring会创建一个ModelMap对象，并传入方法，方法处理完成后自动传递到视图进行处理。

@RequestMapping("/user/list.htm")
public String listAllUser(ModelMap model){
    List<User> users = new ArrayList<User>();
    User user = new User();
    user.setPassword("user1");
    user.setPassword("pwd");
    user.setAge(20);
    users.add(user);

    user = new User();
    user.setPassword("user2");
    user.setPassword("pwd2");
    user.setAge(22);
    users.add(user);

    model.addAttribute("users", users);
    return "user/list-user";
}

	@RequestMapping("/user/list.htm")
	public String listAllUser(ModelMap model){
		List<User> users = new ArrayList<User>();
		User user = new User();
		user.setPassword("user1");
		user.setPassword("pwd");
		user.setAge(20);
		users.add(user);
		
		user = new User();
		user.setPassword("user2");
		user.setPassword("pwd2");
		user.setAge(22);
		users.add(user);
		
		model.addAttribute("users", users);
		return "user/list-user";
	}

model中的参数默认是添加在request作用域中的，该例中视图可以通过request.getAttribute("users")获得user列表。在视图中使用jstl输出

<c:forEach var="user" items="${requestScope.users}">
    ${user.username }
    ${user.password }
    ${user.age }
</c:forEach>

<c:forEach var="user" items="${requestScope.users}">
	${user.username }
	${user.password }
	${user.age }
</c:forEach>

还可以通过在Controller方法返回一个ModelMap对象，这种情况下，视图名由请求Url确定。

@RequestMapping("/user/list-user.htm")
public ModelMap listAllUser() {
    List<User> users = new ArrayList<User>();
    //.........
    ModelMap model = new ModelMap();
    model.addAttribute("users", users);
    return model;
}

	@RequestMapping("/user/list-user.htm")
	public ModelMap listAllUser() {
		List<User> users = new ArrayList<User>();
		//.........
		ModelMap model = new ModelMap();
		model.addAttribute("users", users);
		return model;
	}

另外可以通过在Controller上添加@SessionAttributes注解指定某个model参数为session作用域的

六：特殊输入参数

spring mvc还可以往Controller方法传入request，session等特殊的参数。

@Controller
public class RequestController {

    @RequestMapping("/handleRequest.htm")
    public void handleRequest(HttpServletRequest request,
            HttpServletResponse response, HttpSession session)
            throws IOException {
        String param = (String) request.getParameter("param");
        if (param != null) {
            session.setAttribute("param", param);
        }
        PrintWriter out = response.getWriter();
        out.println("<h1>" + session.getAttribute("param") + "</h1>");
        out.flush();
        out.close();
    }
}

@Controller
public class RequestController {

	@RequestMapping("/handleRequest.htm")
	public void handleRequest(HttpServletRequest request,
			HttpServletResponse response, HttpSession session)
			throws IOException {
		String param = (String) request.getParameter("param");
		if (param != null) {
			session.setAttribute("param", param);
		}
		PrintWriter out = response.getWriter();
		out.println("<h1>" + session.getAttribute("param") + "</h1>");
		out.flush();
		out.close();
	}
}

 如果在Controller方法中直接使用了response输入，方法应该返回void，不再使用视图。

七：处理文件上传

在前面的例子中配置了multipartResolver bean。该bean对http请求中的mutipart form data进行处理。spring mvc默认支持common fileupload 和 cos 所以需要把相应的jar包放入lib中。

@Controller
public class FileUploadController {
    @RequestMapping("/fileupload.htm")
    public void upload(MultipartHttpServletRequest request,
            HttpServletResponse response) throws IOException {
        MultipartFile file = request.getFile("file");
        byte[] buffer = new byte[1024];
        int len = -1;
        InputStream in = file.getInputStream();
        String contextPath = request.getRealPath("/");
        String path = contextPath + "\\" + file.getOriginalFilename();
        OutputStream out = new FileOutputStream(path);
        while ((len = in.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
        in.close();
        out.close();
        response.getWriter().println("Upload Success!");
    }
}

@Controller
public class FileUploadController {
	@RequestMapping("/fileupload.htm")
	public void upload(MultipartHttpServletRequest request,
			HttpServletResponse response) throws IOException {
		MultipartFile file = request.getFile("file");
		byte[] buffer = new byte[1024];
		int len = -1;
		InputStream in = file.getInputStream();
		String contextPath = request.getRealPath("/");
		String path = contextPath + "\\" + file.getOriginalFilename();
		OutputStream out = new FileOutputStream(path);
		while ((len = in.read(buffer)) != -1) {
			out.write(buffer, 0, len);
		}
		in.close();
		out.close();
		response.getWriter().println("Upload Success!");
	}
}

 MultipartHttpServletRequest可以获得多个上传文件，同时可以获得传入的其他Http参数。

八：异常处理

<bean id="exceptionResolver"
 class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
      <property name="defaultErrorView">
          <value>/exception/error</value>
      </property>
      <property name="exceptionMappings">
          <props>
              <prop key="java.sql.SQLException">
                 /exception/dberror
             </prop>
         </props>
     </property>
</bean>

   <bean id="exceptionResolver"  
    class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">  
         <property name="defaultErrorView">  
             <value>/exception/error</value>  
         </property>  
         <property name="exceptionMappings">  
             <props>  
                 <prop key="java.sql.SQLException">  
                    /exception/dberror  
                </prop>  
            </props>  
        </property>  
   </bean>