Springboot做文件上传和文件下载

新建一个web工程
一、springboot完成，它有一个项目名 Project

准备一份upload.html

上传
1.1 有一个文件上传表单，点击上传一个文件到服务器中，服务器将它存在一个文件夹中。
1.2 上传失败，转发回到upload.html
1.3 上传成功，重定向到download.html，并将需要下载的文件名传送过去

准备一份download.html
2. 下载
点击下载，将前面传送过来的文件又下载下来

注意，下载的文件名不是写死的，和刚才上传的文件名是同名的

package com.example.demo.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


public class FileInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        HttpSession session = request.getSession();
        Object user = session.getAttribute("user");
        if (user != null){
            return true;//登录
        }
        return false;//游客
    }
}

package com.example.demo.config;

import com.example.demo.interceptor.FileInterceptor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.*;

@Configuration
public class MvcConfig implements WebMvcConfigurer {
    @Value("${fileupload.pathname}")
    private String path;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        InterceptorRegistration ir = registry.addInterceptor(new FileInterceptor());//相当于 
五、web层 FileController 
我觉得难点就是如何获取上传的文件名进行下载，我这边用了不太好的一个方法，用了list去存取，声明在全局变量上，老师说可以用RESTFUL风格直接在路径上传文件名，但我没搞出来，先这样吧。
 
package com.example.demo.web;

import com.example.demo.util.DownloadUtil;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.ArrayList;
import java.util.List;

@Controller
public class FileController {
    private List list = new ArrayList();
    
    @RequestMapping("/login")
    public String login(){
        return "upload";
    }

    @RequestMapping("/xiazai")
    public String xiazai(){
        return "download";
    }

    
    @RequestMapping("/upload")
    public String upload(Model model,MultipartFile pic,
                         @Value("${fileupload.pathname}") String path) throws IOException {
        if (!pic.isEmpty()){
            pic.transferTo(new File(path,pic.getOriginalFilename()));
            list.add(pic.getOriginalFilename());
            return "redirect:/xiazai";
        }else {
            model.addAttribute("tip","上传失败，请重新选择文件。");
            return "upload";
        }
    }

    
    @RequestMapping("/download")
    public void download( HttpServletResponse resp,
                           @RequestHeader("User-Agent") String userAgent,@Value("${fileupload.pathname}") String path) throws Exception {
        String filename = (String) list.get(list.size()-1);
        String filenameEncoding = DownloadUtil.filenameEncoding(filename, userAgent);
        resp.setHeader("Content-Disposition","attachment;filename="+filenameEncoding);
        InputStream is = new FileInputStream(path + "\"+ filename);
        OutputStream os = resp.getOutputStream();
        byte[] buf = new byte[1024];
        int len = -1;
        while ((len = is.read(buf)) != -1){
            os.write(buf,0,len);
        }
        os.flush();
        os.close();
        is.close();
    }
}

 
DemoApplication和pom.xml是框架自动生成的，就不复制过来了。application.properties里加一句话：
 fileupload.pathname=d:upload
 然后在D盘下再手动建一个upload的文件夹，用来存放上传的文件。
 
六、准备两个页面 
download.html
 



    
    


    
    

        点我下载
    


 
upload.html
 



    
    


    
文件上传
    

    

        
文件: