Jsp+Servlet实现文件上传下载文件上传（一）

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