参考链接：
FileUpload – Home
Commons IO – Commons IO Overview
一、不推荐的上传文件的逻辑（代码繁琐逻辑简单）
index15_upload.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>upload</title>
</head>
<body>
<%--<form action="servlet14_Upload" method="get">--%>
<%--<form action="servlet14_Upload" method="post">--%>
<form action="servlet14_Upload" method="post" enctype="multipart/form-data">
<input type="file" name="file">
<input type="submit" value="提交上传的文件">
</form>
<p>可以提交文件、图片等文件</p>
<p>如果提交的txt文件后台直接读取txt文件中的字符串</p>
</body>
</html>Servlet14_Upload.java
package com.test.app;
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.*;
/**
* @author:
* @date:2022/1/18
* @description:
*/
@WebServlet("/servlet14_Upload")
public class Servlet14_Upload extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//String file=req.getParameter("file");
// file==null 原因是以字符串形式去取取文本是取不到的，应该以流的形式去取
//字节流
InputStream inputStream = req.getInputStream();
/*
//这里先注释掉，否则后面读取不到inputStream
int temp = 0;
while ((temp = inputStream.read()) != -1) {
//读取图片的二进制流---打印出来显示的都是数字
System.out.println(temp);
}
*/
//InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
//Reader reader = new InputStreamReader(inputStream);//不加UTF-8乱码但是后续写入文件就不乱码了
Reader reader = new InputStreamReader(inputStream,"UTF-8");
BufferedReader bufferedReader = new BufferedReader(reader);
//通过输出流将数据输出到本地硬盘存储起来
//获取文件夹绝对路径--out的绝对路径相关
//String path = req.getServletContext().getRealPath("/file/copy.jpg");
String path = req.getServletContext().getRealPath("/file/copy.txt");
OutputStream outputStream = new FileOutputStream(path);
//WebDemo\out\artifacts\ServeletPractice_war_exploded\file\copy.txt (系统找不到指定的路径。)
//需要提前创建好文件夹file
Writer writer = new OutputStreamWriter(outputStream);
BufferedWriter bufferedWriter = new BufferedWriter(writer);
String str = "";
while ((str = bufferedReader.readLine()) != null) {
System.out.println(str);//打印
bufferedWriter.write(str);//输出保存
}
/*String str_reaad = "";
while ((str_reaad=bufferedReader.readLine())!=null) {
System.out.println(str_reaad);
}
String str_write = "";
while ((str_write=bufferedReader.readLine())!=null) {
System.out.println(str_write);
}*/
bufferedWriter.close();
writer.close();
bufferedReader.close();
reader.close();
inputStream.close();
//
//
}
}
二、推荐的upload file逻辑
下载commons-fileupload-1.4.jar和commons-io-2.11.0.jar引用到工程中
Servlet14_Upload.java
package com.test.app;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
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.*;
import java.util.List;
/**
* @author:
* @date:2022/1/18
* @description:
*/
@WebServlet("/servlet14_Upload")
public class Servlet14_Upload extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
try {
DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();
ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);
List<FileItem> fileItemList = servletFileUpload.parseRequest(req);
System.out.println(fileItemList);
for (FileItem fileItem : fileItemList) {
System.out.println(fileItem.getName());
System.out.println(fileItem.getFieldName());//获取表单提交时候的name属性值
//如果fileItem.isFormField()==true表示它是一个文本，浏览器中可能体现为一个输入框
if (fileItem.isFormField()) {
String name = fileItem.getFieldName();
String value = fileItem.getString("UTF-8");
System.out.println(name + "\t" + value);
//如果fileItem.isFormField()==true表示它是一个文件
} else {
//1、整行读取是读不出换行符号的
//2、按字节读取可以读出换行符
//3、按字符读取的时候如果遇到图片文件，由于不是按照字节读取，图片数据的内部结构被破坏。
String fileName = fileItem.getName();
long size = fileItem.getSize();
System.out.println(fileName + ":" + size + "Byte");
String path = req.getServletContext().getRealPath("file/" + fileName);
InputStream inputStream = fileItem.getInputStream();
OutputStream outputStream = new FileOutputStream(path);
int temp = 0;
while ((temp = inputStream.read()) != -1) {
outputStream.write(temp);
}
outputStream.close();
inputStream.close();
System.out.println("上传成功");
/**
String fileName = fileItem.getName();
long size = fileItem.getSize();
System.out.println(fileName + ":" + size + "Byte");
String path = req.getServletContext().getRealPath("file/" + fileName);
InputStream inputStream = fileItem.getInputStream();
OutputStream outputStream = new FileOutputStream(path);
Reader reader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(reader);
Writer writer = new OutputStreamWriter(outputStream);
BufferedWriter bufferedWriter = new BufferedWriter(writer);
String temp = null;
while ((temp = bufferedReader.readLine()) != null) {
bufferedWriter.write(temp);
}
//整行读取是读不出换行符号的
//按字节读取可以读出换行符
bufferedWriter.close();
writer.close();
outputStream.close();
bufferedReader.close();
reader.close();
inputStream.close();
System.out.println("上传成功");
*/
}
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
protected void doPost_not_recommened(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//String file=req.getParameter("file");
// file==null 原因是以字符串形式去取取文本是取不到的，应该以流的形式去取
//字节流
InputStream inputStream = req.getInputStream();
/*
int temp = 0;
while ((temp = inputStream.read()) != -1) {
//读取图片的二进制流---打印出来显示的都是数字
System.out.println(temp);
}
*/
//InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
//Reader reader = new InputStreamReader(inputStream);//不加UTF-8乱码但是后续写入文件就不乱码了
Reader reader = new InputStreamReader(inputStream, "UTF-8");
BufferedReader bufferedReader = new BufferedReader(reader);
//通过输出流将数据输出到本地硬盘存储起来
//获取文件夹绝对路径--out的绝对路径相关
//String path = req.getServletContext().getRealPath("/file/copy.jpg");
String path = req.getServletContext().getRealPath("/file/copy.txt");
OutputStream outputStream = new FileOutputStream(path);
//WebDemo\out\artifacts\ServeletPractice_war_exploded\file\copy.txt (系统找不到指定的路径。)
//需要提前创建好文件夹file
Writer writer = new OutputStreamWriter(outputStream);
BufferedWriter bufferedWriter = new BufferedWriter(writer);
String str = "";
while ((str = bufferedReader.readLine()) != null) {
System.out.println(str);
bufferedWriter.write(str);
}
/*String str_reaad = "";
while ((str_reaad=bufferedReader.readLine())!=null) {
System.out.println(str_reaad);
}
String str_write = "";
while ((str_write=bufferedReader.readLine())!=null) {
System.out.println(str_write);
}*/
bufferedWriter.close();
writer.close();
bufferedReader.close();
reader.close();
inputStream.close();
//
//
}
}
index15_upload.jsp
<%--
Created by IntelliJ IDEA.
User: Admin
Date: 2022/1/18
Time: 15:38
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>upload</title>
</head>
<body>
<%--<form action="servlet14_Upload" method="get">--%>
<%--<form action="servlet14_Upload" method="post">--%>
<form action="servlet14_Upload" method="post" enctype="multipart/form-data">
上传文件：<input type="file" name="file"> <br/>
上传图片：<input type="file" name="img"> <br/>
上传文本：<input type="file" name="text"> <br/>
上传desc：<input type="text" name="desc"> <br/>
<input type="submit" value="提交上传的文件"> <br/>
</form>
<p>可以提交文件、图片等文件</p>
<p>如果提交的txt文件后台直接读取txt文件中的字符串</p>
</body>
</html>
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