前言：
本文内容：文件传输原理及介绍、文件上传
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文件传输原理及介绍
文件传输原理流程图
准备工作
-
文件上传的jar包下载
- commons-io
- commons-fileUpload
-
把jar包导入项目
-
使用类介绍
【文件上传的注意事项】
- 为了保证服务器安全，上传文件应该放在外界无法直接访问的目录下，例如WEB-INF目录下
- 为了防止文件覆盖的现象发生，上传文件应生成唯一的文件名
- 要限制上传文件的最大值
- 可以限制上传文件的类型，再收到上传文件名时，判断后缀名是否合法
【需要用到的类】
ServletFileUpload负责处理上传的文件数据，并将表单中每个输入项封装成一个FileItem对象，再使用ServletFileUpload对象解析请求时需要DiskFileItemFactory对象。- 我们需要在进行解析工作前构造好
DiskFileItemFactory对象，通过ServletFileUpload对象的构造方法或setFileItemFactory()方法设置ServletFileUpload对象的FileItemFactory属性
-
准备工作完成
文件上传
FileItem类
在Html页面input必须要有name<input type="file" name="file1">
表单如果包含一个文件上传输入，则这个表单的enctype属性必须设置为multipart/form-data
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| <%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>文件上传</title>
</head>
<body>
<%-- 通过表单上传--%>
<form action="${pageContext.request.contextPath}/upload.do" method="post" enctype="multipart/form-data">
<%-- get有上传大小限制--%>
<input type="file" name="file1"><br>
<input type="file" name="file2"><br>
<input type="submit">
<input type="reset">
</form>
</body>
</html>
|
ServletFileUpload类
ServletFileUpload负责处理上传的文件数据，并将表单中每个输入法封装成一个FileItem对象中，使用parseRequest(HttpServletRequest)方法可以通过表单当中每一个HTML标签提交的数据封装为一个FileItem对象，然后以List列表的形式返回，使用该方法处理文件上传。
FileUpload.java
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| package com.jokerdig.servlet;
import org.apache.commons.fileupload.FileItem;
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.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.List;
import java.util.UUID;
public class FileUpload extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
if(!ServletFileUpload.isMultipartContent(req)){
return ;
}
String uploadPath = this.getServletContext().getRealPath("/WEB-INF/upload");
File uploadFile = new File(uploadPath);
if(!uploadFile.exists()){
uploadFile.mkdir();
}
String tmpPath = this.getServletContext().getRealPath("/WEB-INF/tmp");
File tmpFile = new File(tmpPath);
if(!tmpFile.exists()){
tmpFile.mkdir();
}
DiskFileItemFactory factory = getDiskFileItemFactory(tmpFile);
ServletFileUpload upload = getServletFileUpload(factory);
String msg = getParseRequest(upload,req,uploadPath);
req.setAttribute("msg",msg);
req.getRequestDispatcher("info.jsp").forward(req,resp);
}
public static DiskFileItemFactory getDiskFileItemFactory(File file){
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(1024*1024);
factory.setRepository(file);
return factory;
}
public static ServletFileUpload getServletFileUpload(DiskFileItemFactory factory) {
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setProgressListener(new ProgressListener() {
@Override
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println("总大小："+pContentLength+"已上传："+pBytesRead);
}
});
upload.setHeaderEncoding("utf-8");
upload.setFileSizeMax(1024*1024*10);
upload.setSizeMax(1024*1024*10);
return upload;
}
public static String getParseRequest(ServletFileUpload upload,HttpServletRequest req,String uploadPath){
List<FileItem> fileItems = null;
String msg = null;
try {
fileItems = upload.parseRequest(req);
for (FileItem fileItem : fileItems) {
if(fileItem.isFormField()){
String name = fileItem.getFieldName();
String value = fileItem.getString("utf-8");
System.out.println(name+":"+value);
}else{
String uploadFileName = fileItem.getName();
if(uploadFileName.trim().equals("")||uploadFileName==null){
continue;
}
String fileName = uploadFileName.substring(uploadFileName.lastIndexOf("/")+1);
String fileExtName = uploadFileName.substring(uploadFileName.lastIndexOf(".")+1);
String uuidPath = UUID.randomUUID().toString();
String realPath = uploadPath+"/"+uuidPath;
File realPathFile = new File (realPath);
if(!realPathFile.exists()){
realPathFile.mkdir();
}
InputStream inputStream = fileItem.getInputStream();
FileOutputStream os = new FileOutputStream(realPath+"/"+fileName);
byte[] buffer = new byte[1024*1024];
int len = 0;
while((len=inputStream.read(buffer))>0){
os.write(buffer,0,len);
}
os.close();;
inputStream.close();
msg="文件上传成功";
fileItem.delete();
}
}
} catch (Exception e) {
e.printStackTrace();
}
return msg;
}
}
|
web.xml
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<servlet>
<servlet-name>FileUpload</servlet-name>
<servlet-class>com.jokerdig.servlet.FileUpload</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileUpload</servlet-name>
<url-pattern>/upload.do</url-pattern>
</servlet-mapping>
|
上传文件成功
