spring的上传下载

package com.pk.web.controller;
 
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import java.io.*;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
 
@Controller
@RequestMapping("file")
public class UploadController {
    @RequestMapping("/upload.do")
    public String upload(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
               // 这里我用到了jar包
        CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver(
                request.getSession().getServletContext());
        if (multipartResolver.isMultipart(request)) {
            MultipartHttpServletRequest multiRequest = (MultipartHttpServletRequest) request;
 
            Iterator<String> iter = multiRequest.getFileNames();
            while (iter.hasNext()) {
                MultipartFile file = multiRequest.getFile((String) iter.next());
                if (file != null) {
                    String fileName = file.getOriginalFilename();
 
                    String path1 = Thread.currentThread()
                            .getContextClassLoader().getResource("").getPath()
                            + "download" + File.separator;
 
                    //  下面的加的日期是为了防止上传的名字一样
                    String path = path1
                            + new SimpleDateFormat("yyyyMMddHHmmss")
                                    .format(new Date()) + fileName;
 
                    File localFile = new File(path);
 
                    file.transferTo(localFile);
                }
 
            }
 
        }
        return "uploadSuccess";
 
    }
    @RequestMapping("/toUpload.do")
    public String toUpload() {
        return "upload";
    }
 
    @RequestMapping("/download")
    public String download(String fileName, HttpServletRequest request,
            HttpServletResponse response) {
        response.setCharacterEncoding("utf-8");
        response.setContentType("multipart/form-data");
        response.setHeader("Content-Disposition", "attachment;fileName="
                + fileName);
        try {
            String path = Thread.currentThread().getContextClassLoader()
                    .getResource("").getPath()
                    + "download";//这个download目录为啥建立在classes下的
            InputStream inputStream = new FileInputStream(new File(path
                    + File.separator + fileName));
 
            OutputStream os = response.getOutputStream();
            byte[] b = new byte[2048];
            int length;
            while ((length = inputStream.read(b)) > 0) {
                os.write(b, 0, length);
            }
 
             // 这里主要关闭。
            os.close();
 
            inputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
            //  返回值要注意，要不然就出现下面这句错误！
            //java+getOutputStream() has already been called for this response
        return null;
    }
}
还有 上传 配置文件注意






    <!-- mvc注解驱动 -->


    <mvc:annotation-driven/>


    <!-- 扫描器已经有了上面这个mvc注解驱动的功能了，所有不需要了 -->


    <context:component-scan base-package="com.pk.web.controller" />






    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">


        <property name="defaultEncoding" value="utf-8" />


        <property name="maxUploadSize" value="104857600"/>


        <property name="maxInMemorySize" value="4096"/>


    </bean>














    <!-- 前缀+ viewName +后缀 -->


    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">


        <!-- webroot到某一指定的文件夹的路径 -->


        <property name="prefix" value="/WEB-INF/jsp/"></property>


      <!--  自己在你的 /WEB-INF/jsp下建立给jsp见面吧。或者该我上面的配置 -->


        <!-- 视图名称的后缀 -->


        <property name="suffix" value=".jsp"></property>


    </bean>


这里是html 点击下载，这里就写死了（你可以修改成你自己放的文件）。可以修改的。


  <a href="file/download.do?fileName=map.txt">下载1 </a><br />


下面这里是上传代码




   <form action="file/upload.do" method="post" enctype="multipart/form-data">


            选择文件<input type="file" name="file">


            <input type="submit" value="上传">


        </form>






web.xml 配置文件


<servlet>


        <servlet-name>springmvc</servlet-name>


        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>


        <load-on-startup>1</load-on-startup>






    </servlet>






    <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>


        <init-param>


            <param-name>forceEncoding</param-name>


            <param-value>true</param-value>


        </init-param>


    </filter>






    <filter-mapping>


        <filter-name>encodingFilter</filter-name>


        <url-pattern>/*</url-pattern>


    </filter-mapping>






    <servlet-mapping>


        <servlet-name>springmvc</servlet-name>


        <!-- struts习惯使用/*，在springmvc不管用 -->


        <url-pattern>*.do</url-pattern>


    </servlet-mapping>






每个方法都返回的是一个ActionForward对象，而response是ActionForward对象参数，所以就会使response冲突！ 
所以处理上传的action返回null就可以了


最终我把action里的最后 “return SUCCESS ” 改成了 “return null ”   成功了 ！！！