Spring MVC—拦截器，文件上传，中文乱码处理，Rest风格，异常处理机制

• 拦截器
• 文件上传
• -中文乱码解决
• rest风格
• 异常处理机制

---

拦截器

Spring MVC可以使用拦截器对请求进行拦截处理，用户可以自定义拦截器来实现特定的功能，自定义的拦截器必须实现HandlerInterceptor接口，重写以下3个方法。

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
            Object handler) throws Exception {
        // TODO Auto-generated method stub
        String a = request.getParameter("a");
        if(a.equals("10")){
            //通过
            return true;
        }else{
            //不通过
            response.sendRedirect("../inter2.jsp");
        }
        return false;
    }

    /**
     * 在渲染View之后被调用，可以用来释放资源
     */
    @Override
    public void afterCompletion(HttpServletRequest arg0,
            HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        // TODO Auto-generated method stub

    }

    /**
     * 在调用目标方法之后，在渲染界面之前被启用
     * 可以对模型及数据进行调整
     */
    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1,
            Object arg2, ModelAndView arg3) throws Exception {
        // TODO Auto-generated method stub

    }

---

文件上传

导包

commons-fileupload-1.2.jar

import java.io.File;
import java.io.IOException;

import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.multipart.MultipartFile;

@Controller
@RequestMapping("/upload")
public class UploadController {

    @RequestMapping("/l1")
    public String upload(MultipartFile file,HttpSession session) throws IllegalStateException, IOException{
        //验证文件是否为空
        if(!file.isEmpty()) {
            //文件命名:当前时间毫秒数+原图的名字
            String fileName=System.currentTimeMillis()+file.getOriginalFilename();
            //服务器的上传路径
            String location=session.getServletContext().getRealPath("upload");
            //上传文件
            file.transferTo(new File(location+"/"+fileName));
        } 
        return "success";
    }

}

---

-中文乱码解决

在web.xml中进行配置。

  <filter>
   <filter-name>EncodingFilter</filter-name>
   <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
   <init-param>
   <param-name>encoding</param-name>
   <param-value>utf-8</param-value>
   </init-param>
  </filter>
  <filter-mapping>
   <filter-name>EncodingFilter</filter-name>
   <url-pattern>/*</url-pattern>
  </filter-mapping>

---

rest风格：

一种互联网软件架构。
HTTP协议的四种基本操作：

• GET获取资源
• POST新建资源
• PUT更新资源
• DELETE删除资源

rest风格的URL配置：

import java.io.PrintWriter;
import javax.servlet.http.HttpServletRequest;
import org.springframework.http.HttpMethod;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("/rest")
public class RestController {

    @RequestMapping("/r1")
    public void r1(HttpServletRequest request,PrintWriter pw){
        System.out.println(request.getMethod());
        switch (request.getMethod()) {
        //获取数据
        case "GET":
            //...
            System.out.println("获取数据");
            break;
        //添加数据
        case "POST":
            //...
            System.out.println("添加数据");
            break;
        //更新数据
        case "PUT":
            //...
            System.out.println("更新数据");
            break;
        //删除数据
        case "DELETE":
            //...
            System.out.println("删除数据");
            break;
        }

    }

}

在web.xml中进行rest风格组件相关配置

 <!-- rest风格支持组件(支持表单向提交PUT/DELETE方法) -->
  <filter>
    <filter-name>hidden</filter-name>
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>hidden</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

---

异常处理机制

异常处理机制：将遇到的错误进行封装。

在servlet.xml中配置错误处理解析器。

    <!-- 错误处理解析器 -->
    <!-- <bean
        id="exceptionResolver"
        class="com.jredu.exception.MyExceptionHandler"/> -->

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import com.jredu.entity.User;

@Controller
@RequestMapping("/error")
public class ErrorController {

    @RequestMapping("/e1")
    public String e1(){
        User user=null;
        System.out.println(user.getPwd());
        return "hello";
    }

}

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

/**
 * 异常处理捕获监听器
 * @author Administrator
 *
 */
public class MyExceptionHandler implements HandlerExceptionResolver{

    @Override
    public ModelAndView resolveException(HttpServletRequest request,
            HttpServletResponse response, Object handler, Exception ex) {
        // TODO Auto-generated method stub
        ModelAndView mav=new ModelAndView("exception");
        return mav;
    }

}