jsp+servlet实现简单的上传功能下载

学了才知道，其实，上传与下载并没与我想象中那么难，要想实现上传与下载必须导入下面的包

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前端代码

    下载D:/hello.jsp
    

<%--上传表单必须是post请求方式,必须有enctype="multipart/form-data" --%>

    
    

servlet代码

package Servlet;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.sql.SQLException;

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 javax.servlet.jsp.JspFactory;

import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;

/**
 * Servlet implementation class FileServlet
 */
@WebServlet("/FileServlet")
public class FileServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public FileServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        //获取前台传入的option的值
        String option = request.getParameter("option");
        if("download".equals(option)){
            download(request, response);
        }else if("upload".equals(option)){
            upload(request, response);
        }

        
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
    
    protected void download(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /**
         * 下载
         */
        //方法一：
        /*String fileName = request.getParameter("fileName");
        System.out.println(fileName);
        //拷贝的文件
        String path = "d:/"+fileName;
        Reader fr = new FileReader(path);
        Writer out = response.getWriter();
        //通过设置响应头，告知准备回复给客户端的本次响应的处理方式和格式、大小等附加信息
        response.setHeader("Content-Disposition", "attachment;filename=\""+fileName+"\"");
        response.setHeader("Content-Type", "text/plain");
        int data = fr.read();
        while(data!=-1){
            out.write(data);
            data = fr.read();
            out.flush();
        }
        out.close();
        fr.close();*/
        //方法二：
        String fileName = request.getParameter("fileName");
//      拷贝的文件
        String path = "d:/"+fileName;
//      读取文件
        FileInputStream in = new FileInputStream(path);
//      输出文件
        OutputStream out = response.getOutputStream();
        //通过设置响应头，告知准备回复给客户端的本次响应的处理方式和格式、大小等附加信息
                response.setHeader("Content-Disposition", "attachment;filename=\""+fileName+"\"");
                response.setHeader("Content-Type", "text/plain");
        int n;
        while((n=in.read())!=-1){
            out.write(n);
        }
        in.close();
        out.close();
    }

    protected void upload(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /**
         * 上传
         */
         //使用smartupload类实现上传
        SmartUpload  su = new SmartUpload();
        //获取请求页面的资料，初始化上传信息（pageContext）
        // pageContext = _jspxFactory.getPageContext(this, request, response,
            //null, true, 8192, true);
        //是将请求页面index.jsp页面的信息，初始化到smartupload对象中。请求页面中的信息就存到了su对象中
        su.initialize(JspFactory.getDefaultFactory().getPageContext(this, request, response, null, true, 8192, true));
        try {
            //设置不允许上传的类型
            su.setDeniedFilesList("java,txt");
            //设置最大可以上传5MB文件
            su.setMaxFileSize(5*1024*1024);
            su.upload();
            File saveFile = new File("D:/test");
            su.save(saveFile.getPath());
        } catch (SmartUploadException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        
        //String uname = su.getRequest().getParameter("uname");
    }


}

完整的项目代码已经上传到github中了，其中包括上面说到的要导入的包，访问地址:github

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在学习的过程中如果遇到什么问题，欢迎大家提问。