Spring MVC实现文件上传和下载

<!--文件上传-->
<dependency>
 <groupid>commons-fileupload</groupid>
 <artifactid>commons-fileupload</artifactid>
 <version>1.3.3</version>
</dependency>
<!--servlet-api导入高版本的-->
<dependency>
 <groupid>javax.servlet</groupid>
 <artifactid>javax.servlet-api</artifactid>
 <version>4.0.1</version>
</dependency>

<!--文件上传配置-->
<bean id="multipartresolver" class="org.springframework.web.multipart.commons.commonsmultipartresolver">
 <!-- 请求的编码格式，必须和jsp的pageencoding属性一致，以便正确读取表单的内容，
 默认为iso-8859-1 -->
 <property name="defaultencoding" value="utf-8"/>
 <!-- 上传文件大小上限，单位为字节（10485760=10m） -->
 <property name="maxuploadsize" value="10485760"/>
 <property name="maxinmemorysize" value="40960"/>
</bean>

@restcontroller
public class filecontroller {
    //@requestparam("file") 将name=file控件得到的文件封装成 commonsmultipartfile 对象

    //批量上传 commonsmultipartfile 则为数组即可
    @requestmapping("/upload")
    public string fileupload(@requestparam("file") commonsmultipartfile file, httpservletrequest request) throws ioexception {
        //获取文件名 : file.getoriginalfilename();
        string uploadfilename = file.getoriginalfilename();
        //如果文件名为空，直接回到首页！
        if ("".equals(uploadfilename)) {
            return "redirect:/index.jsp";
        }
        system.out.println("上传文件名 : " + uploadfilename);
        //上传路径保存设置
        string path = request.getservletcontext().getrealpath("/upload");
        //如果路径不存在，创建一个
        file realpath = new file(path);
        if (!realpath.exists()) {
            realpath.mkdir();
        }
        system.out.println("上传文件保存地址：" + realpath);
        inputstream is = file.getinputstream(); //文件输入流
        outputstream os = new fileoutputstream(new file(realpath, uploadfilename)); //文件输出流
        //读取写出
        int len = 0;
        byte[] buffer = new byte[1024];
        while ((len = is.read(buffer)) != -1) {
            os.write(buffer, 0, len);
            os.flush();
        }
        os.close();
        is.close();
        return "redirect:/index.jsp";
    }

    /*
     * 采用file.transto 来保存上传的文件
     */
    @requestmapping("/upload2")
    public string fileupload2(@requestparam("file") commonsmultipartfile file, httpservletrequest request) throws ioexception {
        //上传路径保存设置
        string path = request.getservletcontext().getrealpath("/upload");
        file realpath = new file(path);
        if (!realpath.exists()) {
            realpath.mkdir();
        }
        system.out.println("上传文件保存地址：" + realpath);
        //通过commonsmultipartfile的方法直接写文件（注意这个时候）
        file.transferto(new file(realpath + "/" + file.getoriginalfilename()));
        return "redirect:/index.jsp";
    }
}

@requestmapping(value = "/download")
public string downloads(httpservletresponse response, httpservletrequest request) throws exception {
    //要下载的图片地址
    string path = request.getservletcontext().getrealpath("/upload");
    string filename = "基础语法.jpg";

    //1、设置response 响应头
    response.reset(); //设置页面不缓存,清空buffer
    response.setcharacterencoding("utf-8"); //字符编码
    response.setcontenttype("multipart/form-data"); //二进制传输数据
    //设置响应头
    response.setheader("content-disposition", "attachment;filename=" + urlencoder.encode(filename, "utf-8"));
    file file = new file(path, filename);
    //2、 读取文件--输入流
    inputstream input = new fileinputstream(file);
    //3、 写出文件--输出流
    outputstream out = response.getoutputstream();
    byte[] buff = new byte[1024];
    int index = 0;
    //4、执行 写出操作
    while ((index = input.read(buff)) != -1) {
        out.write(buff, 0, index);
        out.flush();
    }
    out.close();
    input.close();
    return null;
}