springBoot实现上传下载使用的是thymeleaf模板插件

1.在pom.xml中添加配置文件的

		
			org.springframework.boot
			spring-boot-starter-thymeleaf
		

		
		
			org.springframework.boot
			spring-boot-devtools
			true
			true
		

2.在springBoot中添加thymeleaf的配置

#配置thymeleaf的模板模式为HTML5
spring.thymeleaf.mode= HTML5

3.在启动类中配置一个文件上传大小的类

package com.seecen;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.MultipartConfigFactory;
import org.springframework.context.annotation.Bean;

import javax.servlet.MultipartConfigElement;

@MapperScan({"com.seecen.dao","com.seecen.mapper"})
@SpringBootApplication
public class SpringbootdemoApplication {
	public static void main(String[] args) {
		SpringApplication.run(SpringbootdemoApplication.class, args);
	}


	/**
	 * 文件上传配置
	 * @return
	 */
	@Bean
	public MultipartConfigElement multipartConfigElement() {
		MultipartConfigFactory factory = new MultipartConfigFactory();
		//单个文件最大
		factory.setMaxFileSize("10240KB"); //KB,MB
		/// 设置总上传数据总大小
		factory.setMaxRequestSize("102400KB");
		return factory.createMultipartConfig();
	}
}

4.Controller类上传下载实现方法

package com.seecen.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartHttpServletRequest;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.List;

@Controller
public class FileController {

    /**
     * 实现文件上传
     * */
    @RequestMapping("file")
    public String file(@RequestParam("fileName") MultipartFile file,HttpServletResponse response){
        if(file.isEmpty()){
            return "Exception";
        }
        String fileName = file.getOriginalFilename();
        int size = (int) file.getSize();
        System.out.println(fileName + "--" + size);
        String path = "F:/file" ;
        File dest = new File(path + "/" + fileName);
        if(!dest.getParentFile().exists()){ //判断文件父目录是否存在
            dest.getParentFile().mkdir();
        }
        try {
            file.transferTo(dest); //保存文件
            System.out.println("上传成功");
            return "index2";
        } catch (IllegalStateException e) {
            e.printStackTrace();
            return "Exception";
        } catch (IOException e) {
            e.printStackTrace();
            return "Exception";
        }
    }
    
    /**
     * 实现多文件上传
     * */
    @RequestMapping(value="morefile",method= RequestMethod.POST)
    /**public @ResponseBody String multifileUpload(@RequestParam("fileName")List files) */
    public  String multifileUpload(HttpServletRequest request){
        List files = ((MultipartHttpServletRequest)request).getFiles("fileName");

        if(files.isEmpty()){
            return "Exception";
        }
        String path = "F:/file" ;
        for(MultipartFile file:files){
            String fileName = file.getOriginalFilename();
            int size = (int) file.getSize();
            System.out.println(fileName + "--" + size);
            if(file.isEmpty()){
                return "Exception";
            }else{
                File dest = new File(path + "/" + fileName);
                if(!dest.getParentFile().exists()){ //判断文件父目录是否存在
                    dest.getParentFile().mkdir();
                }
                try {
                    file.transferTo(dest);
                }catch (Exception e) {
                    e.printStackTrace();
                    return "Exception";
                }
            }
        }
        return "index2";
    }

    /*
     *文件下载
    */
    @RequestMapping("download")
    public String downLoad(HttpServletResponse response){
        String filename="2.jpg";
        String filePath = "文件" ;
        File file = new File(filePath + "/" + filename);
        if(file.exists()){ //判断文件父目录是否存在
            response.setContentType("application/force-download");
            response.setHeader("Content-Disposition", "attachment;fileName=" + filename);
            byte[] buffer = new byte[1024];
            FileInputStream fis = null; //文件输入流
            BufferedInputStream bis = null;
            OutputStream os = null; //输出流
            try {
                os = response.getOutputStream();
                fis = new FileInputStream(file);
                bis = new BufferedInputStream(fis);
                int i = bis.read(buffer);
                while(i != -1){
                    os.write(buffer);
                    i = bis.read(buffer);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            System.out.println("----------file download" + filename);
            try {
                bis.close();
                fis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }
}

5.上传下载页面

    
    


文件上传

    
选择文件: 
    









    
    


文件上传

    
选择文件1: 
    
选择文件2: 
    
选择文件3: 
    

6.上传成功后进入index页面

注意配置文件中的spring.thymeleaf.prefix=classpath:/templates/表示扫描templates包下的html文件 默认就是扫描templates包下

所以页面需要放在templates下

thymeleaf基本语法教程
https://www.e-learn.cn/thymeleaf