使用javax.servlet.http.Part类上传文件

使用的是Servlet 3.0 新的特征标注（Annotaion）类描述部署，一些低版本的服务器需要使用标准依赖部署描述文件（web.xml）来部署，另外Part也是Java EE 6.0新增的类，Part是一个接口继承于javax.servlet.http，代表一部分表单项目接收来自multipart/form-data的POST的请求。

!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">

    <head>

        <title>上传文件</title>

    </head>

    <body>

        <div class="container">

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

                <table>

                    <tr>

                        <td><label for="file">上传文件：</label></td>

                        <td><input type="file" id="file" name="picture" value=""/></td>

                    </tr>

                    <tr>

                        <td colspan="2"><input type="submit" value="提交"/></td>

                    </tr>

                </table>

            </form>

        </div>

    </body>

</html>

@MultipartConfig

@WebServlet(name = "UploadServlet", urlPatterns = {"/upload.do"})

public class UploadServlet extends HttpServlet {

    private String contextPath;

    @Override

    public void init() throws ServletException {

        contextPath = getServletContext().getRealPath("/");

    }

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");

        Part part = request.getPart("picture");

        String fileName = getFileName(part);

        writeTo(fileName, part);

        //forward到显示

        request.setAttribute("fileName", fileName);

        request.getRequestDispatcher("show.jsp").forward(request, response);

    }

    //取得上传文件名

    private String getFileName(Part part) {

        String header = part.getHeader("Content-Disposition");

        String fileName = header.substring(header.indexOf("filename=\"") + 10,

                header.lastIndexOf("\""));

        return fileName;

    }

    //存储文件

    private void writeTo(String fileName, Part part) throws IOException, FileNotFoundException {

        InputStream in = part.getInputStream();

        OutputStream out = new FileOutputStream(contextPath + fileName);

        byte[] buffer = new byte[1024];

        int length = -1;

        while ((length = in.read(buffer)) != -1) {

            out.write(buffer, 0, length);

        }

        in.close();

        out.close();

    }

}

<!DOCTYPE html>

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

        <title>JSP Page</title>

    </head>

    <body>

        <h1>图片显示</h1>

        <a href="${fileName}">${fileName}</a>

    </body>

</html>

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使用javax.servlet.http.Part类上传文件

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