Java学习笔记-全栈-web开发-12-文件上传和下载

@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet{
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException,IOException {

        //1.判断是否为文件上传表单
        if(ServletFileUpload.isMultipartContent(req)){
            //2.创建个文件工厂
            FileItemFactory factory = new DiskFileItemFactory();
            //3.创建文件上传对象
            ServletFileUpload fileUpload = new ServletFileUpload(factory);

            //4.解析请求
            try{
                List<FileItem> items = fileUpload.parseRequest(req);
                for(FileItem item : items){
                    if(item.isFormField()){//普通表单字段
                        processFormField(item);
                    }else{//文件字段
                        processFile(item);
                    }
                }
            }catch (FileUploadException fue){
                fue.printStackTrace();
            }

        }

    }

    private void processFile(FileItem item) {
        String fieldName = item.getFieldName();
        String fieldValue = item.getString();
        //1.获取文件扩展名
        String suffix = item.getName().split("\\.")[1];
        String saveFileName = UUID.randomUUID().toString() + "." + suffix;
        System.out.println(saveFileName +  ":" + item.getContentType());

        //2.创建文件保存的文件夹
        String folderPath = this.getServletContext().getRealPath("/WEB-INF/upload");//获取项目真实路径
        System.out.println("保存的路径:" + folderPath);
        File file = new File(folderPath);
        if(!file.exists()){
            file.mkdirs();
        }

        //3.保存文件
        //文件完整保存路径
        String filePath = folderPath + "/" + saveFileName;
        try {
            item.write(new File(filePath));
item.delete();//删除临时文件
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void processFormField(FileItem item) {
        String fieldName = item.getFieldName();
        String fieldValue = item.getString();
        System.out.println(fieldName + ":" + fieldValue);
    }
}

<form action="/UploadServlet"  method="post" enctype="multipart/form-data">
    用户名:<input type="text" name="username" placeholder="请输入用户名"><br>
    密码：<input type="password" name="password" placeholder="请输入密码"><br>
    <div id="div1">
        <div>
            <input type="file" name="photo" /><input type="button" value="添加" onclick="addFile()"/><br />
        </div>
    </div>
    <input type="submit" value="提交">
</form>

<script type="text/javascript">
    function addFile(){
        //得到div容器
        var div1 = document.getElementById("div1");
        div1.innerHTML +=  "<div><input type='file' name='photo' /><input type='button' value='删除' οnclick='delFile(this)'/><br /></div>";
    }

    function delFile(input){
        //使用input对象的爷爷删除他的爸爸
        input.parentNode.parentNode.removeChild(input.parentNode);
    }
</script>

@WebServlet("/DownloadServlet")
public class DownloadServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        //1.文件下载的位置
		//此处可通过获取客户端参数然后在数据库中查找是否存在文件
        String filePath = "C:/test.jpg";

        //2.文件名
        String fileName = "img.jpg";
        fileName = URLEncoder.encode(fileName,"UTF-8");//中文名文件需要进行URL编码
        //3.设置响应头
        resp.setHeader("Content-Disposition","attachment;filename=" + fileName);
        resp.setContentType("application/octet-stream");

        //4.响应文件
        File file = new File(filePath);
        InputStream is = new FileInputStream(file);
        byte[] bytes = new byte[1024 * 8];
        int len;
        OutputStream os = resp.getOutputStream();
        while((len = is.read(bytes)) != -1){
            os.write(bytes,0,len);
        }

        //5.关闭流
        is.close();
        os.close();
    }
}