一、实验目的：

掌握Servlet的HttpServletRequest对文件上传的支持；
能够理解文件上传的原理，掌握文件上传与下载的步骤

二、实验要求：

基于Servlet的文件上传。
文件的下载。
熟练使用MYEclipse开发

三、实验内容：

1、单文件上传

uploadHttpOne.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java"  pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
    <title>HttpServletResquest对文件上传的支持</title>
    <meta charset="UTF-8">
</head>
<body>
<form action="uploadHttpOneServlst" method="post" enctype="multipart/form-data">
    <table>
        <tr>
            <td>文件描述：</td>
            <td><input type="text" name="filediscription"></td>
        </tr>
        <tr>
            <td>请选择文件：</td>
            <td><input type="file" name="resPath"></td>

        </tr>
        <tr>
            <td align="right"><input type="reset" value="重填"></td>
            <td><input type="submit" value="上传"></td>
        </tr>
    </table>
</form>
</body>
</html>

UploadHttpOneServlst.java

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;

@MultipartConfig(maxFileSize = 10 * 1024 * 1024)
@WebServlet("/uploadHttpOneServlst")
public class UploadHttpOneServlst extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        request.setCharacterEncoding("UTF-8");
        Part part = request.getPart("resPath");
        String filediscription = request.getParameter("filediscription");
        out.println("输入的文件描述：" + filediscription + "<br/>");
        File uploadFileDir = new File(getServletContext().getRealPath("/uploadFiles"));
        if (!uploadFileDir.exists()) {
            uploadFileDir.mkdir();
        }
        String oldName = MyUtil.getFileName(part);
        out.println("上传文件的原始名：" + oldName + "<br/>");
        out.println("上传文件的大小：" + part.getSize() + "<br/>");
        if (oldName != null) {
            part.write(uploadFileDir + File.separator + oldName);
        }
        out.println("文件上传到：" + uploadFileDir + File.separator + oldName + "<br/>");
    }
}

MyUtil.java

package servlet;

import javax.servlet.http.Part;

public class MyUtil {
    public static String getFileName(Part part) {
        if (part == null)
            return null;
        String fileName = part.getHeader("content-disposition");
        if (fileName.lastIndexOf("=") + 2 == fileName.length() - 1)
            return null;
        return fileName.substring(fileName.lastIndexOf("=") + 2, fileName.length() - 1);
    }
}

运行结果：
在这里插入图片描述

2、多文件上传

UploadHttpMultiServlst.java

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collection;

@MultipartConfig
@WebServlet("/uploadHttpMultiServlst")
public class UploadHttpMultiServlst extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        request.setCharacterEncoding("UTF-8");
        String filediscription1 = request.getParameter("filediscription1");
        out.println("输入的文件1描述：" + filediscription1 + "<br/>");
        String filediscription2 = request.getParameter("filediscription2");
        out.println("输入的文件2描述：" + filediscription2 + "<br/>");
        File uploadFileDir = new File(getServletContext().getRealPath("/uploadFiles"));
        if (!uploadFileDir.exists()) {
            uploadFileDir.mkdir();
        }
        Collection<Part> parts = request.getParts();
        for (Part part : parts) {
            if (part == null || !part.getName().contains("resPat")) {
                continue;
            }
            String oldName = MyUtil.getFileName(part);
            out.println("上传文件的原始名：" + oldName + "<br/>");
            out.println("上传文件的大小：" + part.getSize() + "<br/>");
            if (oldName != null) {
                part.write(uploadFileDir + File.separator + oldName);
            }
            out.println("文件上传到：" + uploadFileDir + File.separator + oldName + "<br/>");
        }
    }
}

MyUtil.java

package servlet;

import javax.servlet.http.Part;

public class MyUtil {
    public static String getFileName(Part part) {
        if (part == null)
            return null;
        String fileName = part.getHeader("content-disposition");
        if (fileName.lastIndexOf("=") + 2 == fileName.length() - 1)
            return null;
        return fileName.substring(fileName.lastIndexOf("=") + 2, fileName.length() - 1);
    }
}

UploadHttpMultiServlst.jsp

<%@ page contentType="text/html;charset=UTF-8" 
language="java" pageEncoding="utf-8" %>
<!DOCTYPE html>
<html>
<head>
    <title>HttpServletResquest对文件上传的支持</title>
    <meta charset="UTF-8">
</head>
<body>
<form action="uploadHttpMultiServlst" method="post" enctype="multipart/form-data">
    <table>
        <tr>
            <td>文件1描述：</td>
            <td><input type="text" name="filediscription1"></td>
        </tr>
        <tr>
            <td>请选择文件1：</td>
            <td><input type="file" name="resPath1"></td>

        </tr>
        <tr>
            <td>文件2描述：</td>
            <td><input type="text" name="filediscription2"></td>
        </tr>
        <tr>
            <td>请选择文件2：</td>
            <td><input type="file" name="resPath2"></td>

        </tr>
        <tr>
            <td align="right"><input type="reset" value="重填"></td>
            <td><input type="submit" value="上传"></td>
        </tr>
    </table>
</form>
</body>
</html>

运行结果：
在这里插入图片描述

3、上传文件的大小限定

对多文件上传实例文件大小进行限定！
仅仅在UploadHttpMultiServlst.Java中加上限制条件——@MultipartConfig(maxFileSize = 10 * 1024 * 1024)//设置上传文件的最大值为10MB,其他代码不用变！
UploadHttpMultiServlst.Java

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collection;

@MultipartConfig(maxFileSize = 10 * 1024 * 1024)//设置上传文件的最大值为10MB
@WebServlet("/uploadHttpMultiServlst")
public class UploadHttpMultiServlst extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        request.setCharacterEncoding("UTF-8");
        String filediscription1 = request.getParameter("filediscription1");
        out.println("输入的文件1描述：" + filediscription1 + "<br/>");
        String filediscription2 = request.getParameter("filediscription2");
        out.println("输入的文件2描述：" + filediscription2 + "<br/>");
        File uploadFileDir = new File(getServletContext().getRealPath("/uploadFiles"));
        if (!uploadFileDir.exists()) {
            uploadFileDir.mkdir();
        }
        Collection<Part> parts = request.getParts();
        for (Part part : parts) {
            if (part == null || !part.getName().contains("resPat")) {
                continue;
            }
            String oldName = MyUtil.getFileName(part);
            out.println("上传文件的原始名：" + oldName + "<br/>");
            out.println("上传文件的大小：" + part.getSize() + "<br/>");
            if (oldName != null) {
                part.write(uploadFileDir + File.separator + oldName);
            }
            out.println("文件上传到：" + uploadFileDir + File.separator + oldName + "<br/>");
        }
    }
}

运行结果：
当其中一个文件大小大于10MB时，无法上传文件数据：
在这里插入图片描述

当文件小于10MB时，能够正常上传：

4、实现文件的下载功能，并解决下载乱码问题

实验代码和运行结果如下：
导包：在这里插入图片描述
ShowDownServlet.java

package servlet;

import javax.servlet.RequestDispatcher;
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.IOException;

@WebServlet("/showDownServlet")
public class ShowDownServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //指定从服务器uploadFiles目录中下载文件
        File downLoadFileDir = new File(getServletContext().getRealPath("/uploadFiles"));
        //获得目录中的文件
        File[] list = downLoadFileDir.listFiles();
        request.setAttribute("fileList", list);
        RequestDispatcher dis = request.getRequestDispatcher("showInfo.jsp");
        dis.forward(request, response);

    }
}

MyUtil.java

package servlet;

import javax.servlet.http.Part;
import java.io.UnsupportedEncodingException;

public class MyUtil {
    public static String getFileName(Part part) {
        if (part == null)
            return null;
        String fileName = part.getHeader("content-disposition");
        if (fileName.lastIndexOf("=") + 2 == fileName.length() - 1)
            return null;
        return fileName.substring(fileName.lastIndexOf("=") + 2, fileName.length() - 1);
    }

    //处理乱码问题
    public static String toUTF8String(String str) {
        StringBuffer sb = new StringBuffer();
        int len = str.length();
        for (int i = 0; i < len; i++) {
            char c = str.charAt(i);
            if (c >= 0 && c <= 255) {
                sb.append(c);
            } else {
                byte b[];
                try {
                    b = Character.toString(c).getBytes("UTF-8");
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                    b = null;
                }
                for (int j = 0; j < b.length; j++) {
                    int k = b[j];
                    if (k < 0) {
                        k &= 255;
                    }
                    sb.append("&" + Integer.toHexString(k).toUpperCase());
                }
            }
        }
        return sb.toString();
    }

}

DownloadServlet.java

package servlet;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.FileInputStream;
import java.io.IOException;

@WebServlet("/downloadServlet")
public class DownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        File downLoadFileDir = new File(getServletContext().getRealPath("/uploadFiles"));
        String aFileName = null;
        FileInputStream in = null;
        ServletOutputStream out = null;
        try {
            aFileName = request.getParameter("resPath");
            response.setHeader("Content-Type", "application/x-msdownload");
            response.setHeader("Content-Dissposition", "attachment;filename=" + MyUtil.toUTF8String(aFileName));
            in = new FileInputStream(downLoadFileDir + File.separator + aFileName);
            out = response.getOutputStream();
            out.flush();
            int aRead = 0;
            byte b[] = new byte[1024];
            while ((aRead = in.read(b)) != -1 & in != null) {
                out.write(b, 0, aRead);
            }
            out.flush();
            in.close();
            out.close();
        } catch (Throwable e) {
            e.printStackTrace();
        }

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

showInfo.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" pageEncoding="utf-8" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
    <title>显示下载文件</title>
    <meta charset="UTF-8">
</head>
<body>
<form action="uploadHttpMultiServlst" method="post" enctype="multipart/form-data">
    <table border="1">
        <tr bgcolor="#90ee90">
            <th>文件名称</th>
            <th>下载课件</th>
        </tr>
        <c:forEach var="afile" items="${fileList}">
            <tr>
                <td>${afile.name}</td>
                <td align="center"><a href="downloadServlet?resPath=${afile.name}"
                                      style="text-decoration: yellow">下载</a></td>
            </tr>
        </c:forEach>
    </table>
</form>
</body>
</html>