使用Servlet实现上传文件功能

Posted 2020-10-01 Dolphin

1.servlet只需加上一个注释和用request.getPart来获取文件的值，这是servlet3.0的API

2.表单需要加上一个属性enctype="multipart/form-data"

 

现在附上代码

表单：

 <form method="POST" action="upload" enctype="multipart/form-data" >
            File:
            <input type="file" name="file" id="file" /> <br/>
            Destination:
            <input type="text" value="f:" name="destination"/>
            <br/>
            <input type="submit" value="Upload" name="upload" id="upload" />
</form>

 

servlet：

在类的声名上加上这两个注释

@WebServlet(name = "FileUploadServlet", urlPatterns = {"/upload"})
@MultipartConfig

自定义的方法：

processRequest方法是获取文件的值的

protected void processRequest(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
　　　　　　request.setCharacterEncoding("utf-8");
　　　　　　
　　　　　//获取路径
        final String path = request.getParameter("destination");
　　　　　//获取文件的值
        final Part filePart = request.getPart("file");
        System.out.println(filePart);
        final String fileName = getFileName(filePart);
　　　　　//使用IO流对文件进行操作
        OutputStream out = null;
        InputStream filecontent = null;
        final PrintWriter writer = response.getWriter();

        try {
            out = new FileOutputStream(new File(path + File.separator
                    + fileName));
            filecontent = filePart.getInputStream();

            int read;
            final byte[] bytes = new byte[1024];

            while ((read = filecontent.read(bytes)) != -1) {
                out.write(bytes, 0, read);
            }
            writer.println("New file " + fileName + " created at " + path);
            LOGGER.log(Level.INFO, "File {0} being uploaded to {1}",
                    new Object[]{fileName, path});

        } catch (FileNotFoundException fne) {
            writer.println("You either did not specify a file to upload or are "
                    + "trying to upload a file to a protected or nonexistent "
                    + "location.");
            writer.println("<br/> ERROR: " + fne.getMessage());

            LOGGER.log(Level.SEVERE, "Problems during file upload. Error: {0}",
                    new Object[]{fne.getMessage()});
        } finally {
            if (out != null) {
                out.close();
            }
            if (filecontent != null) {
                filecontent.close();
            }
            if (writer != null) {
                writer.close();
            }
        }
    }

 

getFileName方法是获取文件名的

private String getFileName(final Part part) {
final String partHeader = part.getHeader("content-disposition");
LOGGER.log(Level.INFO, "Part Header = {0}", partHeader);
for (String content : part.getHeader("content-disposition").split(";")) {
if (content.trim().startsWith("filename")) {
return content.substring(
content.indexOf(\'=\') + 1).trim().replace("\\"", "");
}
}
return null;
}

 

最后在doPost方法里写

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

到这里就全部完成了，长传成功的效果，如图：