servlet+jsp上传过程（学习记录）

前段jsp代码（简单的表单）：

<form action="${pageContext.request.contextPath}/Upload" enctype="multipart/form-data" method="post">        上传用户：<input type="text" name="username"><br>        上传文件：<input type="file" name="filename"><br>        <input type="submit" value="上传"><br>    </form>

后台servlet代码

需要导入commoms-fileupload和commoms-io包.

---

package lxb.upload;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
* Servlet implementation class Upload
*/
public class Upload extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException        {    //设置编码格式    response.setCharacterEncoding("utf-8");    response.setContentType("text/html ; charset=utf-8");    try {        //设置上传文件类型        List<String> allowList = Arrays.asList(".jpg", ".avi", ".MOV");        DiskFileItemFactory factory = new DiskFileItemFactory();        //设置缓冲大小和缓冲目录        factory.setSizeThreshold(1024*1024);        factory.setRepository(new File("d:\\2345\\"));        //创建上传解析器        ServletFileUpload upload = new ServletFileUpload(factory);        //判断文件是否为普通文件        if (!upload.isMultipartContent(request)) {            return;        }        //设置最大文件上传        upload.setSizeMax(1024*1024*5);        //设置上传文件监听器        upload.setProgressListener(new ProgressListener() {            private int count = 0;            public void update(long pBytesRead, long pContentLength, int pItems) {                if (pBytesRead / (1024 * 1024) > count) {                    count++;                    System.out.println("已经解析了：" + count + "m了");                }            }        });        //解决文件名乱码问题        upload.setHeaderEncoding("UTF-8");        //解析上传文件        List<FileItem> list = upload.parseRequest(request);        //得到表单上传的每个文件        for (FileItem file : list) {            //判断是否为普通表单类型            if (file.isFormField()) {                String name = file.getFieldName();                //对表单传来的中文解析，解决乱码问题                //value = new String(value.getBytes("iso8859-1"), "UTF-8");(这种也可以)                String value = file.getString("UTF-8");                System.out.println(name+".........."+value);            }else{                //得到文件名                String fileName = file.getName();                //判断是否支持文件类型                if (!allowList.contains(fileName.substring(fileName.lastIndexOf(".")))) {                    PrintWriter out = response.getWriter();                    out.println("不支持文件类型");                    return;                }                //生成随机目录和随机文件名                String path = makeName(fileName);                //文件流的传输，                InputStream is = file.getInputStream();                OutputStream os = new FileOutputStream(new File(path));                int len = 0;                byte[] buff = new byte[1024];                while ((len = is.read(buff)) > 0) {                    os.write(buff, 0, len);                    os.flush();                }                //关流很重要，输入流也要关，要不然删不掉临时文件，卡了很久才发现，                is.close();                os.close();                //删除临时文件                file.delete();            }        }        //提示        request.getRequestDispatcher("/message.jsp").forward(request, response);    } catch (FileUploadException e) {        request.getRequestDispatcher("message.jsp").forward(request, response);    } catch (UnsupportedEncodingException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    } catch (ServletException e) {        e.printStackTrace();    }}//生成随机文件路径和文件名private String makeName(String fileName) {    int one = fileName.hashCode();    one = one & 15;    int two = fileName.hashCode();    two = (two >> 4) & 15;    String path = "d:\\2345\\" + one + File.separator + two + File.separator;    File file = new File(path);    if (!file.exists()) {        file.mkdirs();    }    return path + File.separator + UUID.randomUUID().toString() + fileName;}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    doGet(request, response);}

}

总结

自己写代码才会发现很多问题，看着很简单的一个功能写了一天多，总算把功能基本写出来了。
不过还是有个问题没有解决，在设置了上传文件限制为5M后，如果上传超过5M的文件会提示访问页面出错，并且会发送多次请求，后台也不报错，先做一下记录，以后有能力在解决吧。