文件上传和下载功能是Java Web必备技能,很实用。
本文使用的是Apache下的著名的文件上传组件
org.apache.commons.fileupload 实现
下面结合最近看到的一些资料以及自己的尝试,先写第一篇文件上传。后续会逐步实现下载,展示文件列表,上传信息持久化等。
废话少说,直接上代码
第一步,引用jar包,设置上传目录
commons-fileupload-1.3.1.jar
commons-io-2.4.jar
上传目录:WEB-INF/tempFiles和WEB-INF/uploadFiles
第二步,编写JSP页面
<%@ page contentType="text/html;
charset=UTF-8" language="java" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <html> <head> <title>文件上传测试</title> </head> <body> <form method="POST" enctype="multipart/form-data" action="<%=request.getContextPath()%>/UploadServlet"> 文件: <input type="file" name="upfile"><br/> <br/> <input type="submit" value="上传"> </form> <c:if test="${
not empty errorMessage}
"> <input type="text" id="errorMessage" value="${
errorMessage}
" style="color:red;
" disabled="disabled"> </c:if> </body> </html>
第三步,编写Servlet,处理文件上传的核心
package servlet;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
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;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Calendar;
import java.util.Iterator;
import java.util.List;
import java.util.UUID;
/** * 处理文件上传 * * @author xusucheng * @create 2017-12-27 **/ @WebServlet("/UploadServlet") public class UploadServlet extends HttpServlet {
@Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置文件上传基本路径 String savePath = this.getServletContext().getRealPath("/WEB-INF/uploadFiles");
//设置临时文件路径 String tempPath = this.getServletContext().getRealPath("/WEB-INF/tempFiles");
File tempFile = new File(tempPath);
if (!tempFile.exists()) {
tempFile.mkdir();
}
//定义异常消息 String errorMessage = "";
//创建file items工厂 DiskFileItemFactory factory = new DiskFileItemFactory();
//设置缓冲区大小 factory.setSizeThreshold(1024 * 100);
//设置临时文件路径 factory.setRepository(tempFile);
//创建文件上传处理器 ServletFileUpload upload = new ServletFileUpload(factory);
//监听文件上传进度 ProgressListener progressListener = new ProgressListener() {
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println("正在读取文件: " + pItems);
if (pContentLength == -1) {
System.out.println("已读取: " + pBytesRead + " 剩余0");
}
else {
System.out.println("文件总大小:" + pContentLength + " 已读取:" + pBytesRead);
}
}
}
;
upload.setProgressListener(progressListener);
//解决上传文件名的中文乱码 upload.setHeaderEncoding("UTF-8");
//判断提交上来的数据是否是上传表单的数据 if (!ServletFileUpload.isMultipartContent(request)) {
//按照传统方式获取数据 return;
}
//设置上传单个文件的大小的最大值,目前是设置为1024*1024字节,也就是1MB upload.setFileSizeMax(1024 * 1024);
//设置上传文件总量的最大值,最大值=同时上传的多个文件的大小的最大值的和,目前设置为10MB upload.setSizeMax(1024 * 1024 * 10);
try {
//使用ServletFileUpload解析器解析上传数据,解析结果返回的是一个List<FileItem>集合,每一个FileItem对应一个Form表单的输入项 List<FileItem> items = upload.parseRequest(request);
Iterator<FileItem> iterator = items.iterator();
while (iterator.hasNext()) {
FileItem item = iterator.next();
//判断jsp提交过来的是不是文件 if (item.isFormField()) {
errorMessage = "请提交文件!";
break;
}
else {
//文件名 String fileName = item.getName();
if (fileName == null || fileName.trim() == "") {
System.out.println("文件名为空!");
}
//处理不同浏览器提交的文件名带路径问题 fileName = fileName.substring(fileName.lastIndexOf("\") + 1);
//文件扩展名 String fileExtension = fileName.substring(fileName.lastIndexOf(".") + 1);
//判断扩展名是否合法 if (!validExtension(fileExtension)) {
errorMessage = "上传文件非法!";
item.delete();
break;
}
//获得文件输入流 InputStream in = item.getInputStream();
//得到保存文件的名称 String saveFileName = createFileName(fileName);
//得到文件保存路径 String realFilePath = createRealFilePath(savePath, saveFileName);
//创建文件输出流 FileOutputStream out = new FileOutputStream(realFilePath);
//创建缓冲区 byte buffer[] = new byte[1024];
int len = 0;
while ((len = in.read(buffer)) > 0) {
//写文件 out.write(buffer, 0, len);
}
//关闭输入流 in.close();
//关闭输出流 out.close();
//删除临时文件 TODO item.delete();
//将上传文件信息保存到附件表中 TODO }
}
}
catch (FileUploadBase.FileSizeLimitExceededException e) {
e.printStackTrace();
request.setAttribute("errorMessage", "单个文件超出最大值!!!");
request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response);
return;
}
catch (FileUploadBase.SizeLimitExceededException e) {
e.printStackTrace();
request.setAttribute("errorMessage", "上传文件的总的大小超出限制的最大值!!!");
request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response);
return;
}
catch (FileUploadException e) {
e.printStackTrace();
request.setAttribute("errorMessage", "文件上传失败!!!");
request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response);
return;
}
request.setAttribute("errorMessage", errorMessage);
request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response);
}
@Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
private boolean validExtension(String fileExtension) {
String[] exts = {
"jpg", "txt", "doc", "pdf"}
;
for (int i = 0;
i < exts.length;
i++) {
if (fileExtension.equals(exts[i])) {
return true;
}
}
return false;
}
private String createFileName(String fileName) {
return UUID.randomUUID().toString() + "_" + fileName;
}
/** * 根据基本路径和文件名称生成真实文件路径,基本路径\年\月\fileName * * @param basePath * @param fileName * @return */ private String createRealFilePath(String basePath, String fileName) {
Calendar today = Calendar.getInstance();
String year = String.valueOf(today.get(Calendar.YEAR));
String month = String.valueOf(today.get(Calendar.MONTH) + 1);
String upPath = basePath + File.separator + year + File.separator + month + File.separator;
File uploadFolder = new File(upPath);
if (!uploadFolder.exists()) {
uploadFolder.mkdirs();
}
String realFilePath = upPath + fileName;
return realFilePath;
}
}
第四步,测试
http://localhost:8080/helloweb/pages/upload/upload.jsp
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。
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