Spring Boot 实现文件上传，下载

1、 创建Spring Boot项目

2、 创建FileController.java

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;
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;

/**
 * Created by Nominal on 2018/3/23 0023.
 * 微博：@Mr丶Li_Anonym
 */
@Controller
public class FileController {


    @GetMapping("/")
    public String index(){
        return "index";
    }
    private static final Logger logger = LoggerFactory.getLogger(FileController.class);
    //文件上传相关代码
    @RequestMapping(value = "upload")
    @ResponseBody
    public String upload(@RequestParam("test") MultipartFile file) {
        if (file.isEmpty()) {
            return "文件为空";
        }
        // 获取文件名
        String fileName = file.getOriginalFilename();
        logger.info("上传的文件名为：" + fileName);
        // 获取文件的后缀名
        String suffixName = fileName.substring(fileName.lastIndexOf("."));
        logger.info("上传的后缀名为：" + suffixName);
        // 文件上传后的路径
        String filePath = "E://test//";
        // 解决中文问题，liunx下中文路径，图片显示问题
        // fileName = UUID.randomUUID() + suffixName;
        File dest = new File(filePath + fileName);
        // 检测是否存在目录
        if (!dest.getParentFile().exists()) {
            dest.getParentFile().mkdirs();
        }
        try {
            file.transferTo(dest);
            return "上传成功";
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "上传失败";
    }

    //文件下载相关代码
    @RequestMapping("/download")
    public String downloadFile(org.apache.catalina.servlet4preview.http.HttpServletRequest request, HttpServletResponse response){
        String fileName = "FileUploadTests.java";
        if (fileName != null) {
            //当前是从该工程的WEB-INF//File//下获取文件(该目录可以在下面一行代码配置)然后下载到C:\\users\\downloads即本机的默认下载的目录
            String realPath = request.getServletContext().getRealPath(
                    "//WEB-INF//");
            File file = new File(realPath, fileName);
            if (file.exists()) {
                response.setContentType("application/force-download");// 设置强制下载不打开
                response.addHeader("Content-Disposition",
                        "attachment;fileName=" +  fileName);// 设置文件名
                byte[] buffer = new byte[1024];
                FileInputStream fis = null;
                BufferedInputStream bis = null;
                try {
                    fis = new FileInputStream(file);
                    bis = new BufferedInputStream(fis);
                    OutputStream os = response.getOutputStream();
                    int i = bis.read(buffer);
                    while (i != -1) {
                        os.write(buffer, 0, i);
                        i = bis.read(buffer);
                    }
                    System.out.println("success");
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (bis != null) {
                        try {
                            bis.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                    if (fis != null) {
                        try {
                            fis.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
        return null;
    }
    //多文件上传
    @RequestMapping(value = "/batch/upload", method = RequestMethod.POST)
    @ResponseBody
    public String handleFileUpload(HttpServletRequest request) {
        List<MultipartFile> files = ((MultipartHttpServletRequest) request)
                .getFiles("file");
        MultipartFile file = null;
        BufferedOutputStream stream = null;
        for (int i = 0; i < files.size(); ++i) {
            file = files.get(i);
            if (!file.isEmpty()) {
                try {
                    byte[] bytes = file.getBytes();
                    stream = new BufferedOutputStream(new FileOutputStream(
                            new File(file.getOriginalFilename())));
                    stream.write(bytes);
                    stream.close();

                } catch (Exception e) {
                    stream = null;
                    return "你没有上传 " + i + " => "
                            + e.getMessage();
                }
            } else {
                return "你没有上传 " + i
                        + " 因为文件是空的.";
            }
        }
        return "上传成功";
    }
}

3、 创建index.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8"/>
    <title>文件上传下载</title>
</head>
<body>
<form action="/upload" method="POST" enctype="multipart/form-data">
    文件：<input type="file" name="test"/></br>
    <input type="submit" />
</form>
<a href="/download">下载test</a>
<p>多文件上传</p>
<form method="POST" enctype="multipart/form-data" action="/batch/upload">
    文件1：<input type="file" name="file" /></br>
    文件2：<input type="file" name="file" /></br>
    <input type="submit" value="上传" /></br>
</form>
</body>
</html>

4、 遇到的问题

1） 上传文件大小限制

解决方法：
新建一个java 配置类FileConfig.java

    import org.springframework.boot.web.servlet.MultipartConfigFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.servlet.MultipartConfigElement;

/**
 * Created by Nominal on 2018/3/23 0023.
 * 微博：@Mr丶Li_Anonym
 */
@Configuration
public class FileConfig {

    /**
     * 文件上传配置
     * @return
     */
    @Bean
    public MultipartConfigElement multipartConfigElement() {
        MultipartConfigFactory factory = new MultipartConfigFactory();
        //单个文件最大
        factory.setMaxFileSize("100MB"); //KB,MB
        /// 设置总上传数据总大小
        factory.setMaxRequestSize("1000MB");
        return factory.createMultipartConfig();
    }
}

2） 上传路径设置到项目相对路径

java.io.IOException: java.io.FileNotFoundException: C:\Users\Administrator\AppData\Local\Temp\tomcat.2415548073766838039.8080\work\Tomcat\localhost\ROOT\upload\bitbug_favicon.ico (系统找不到指定的路径。)

暂无方法解决：建议使用绝对路径（如有大神看到此博客，有解决方法，请在下面评论去帮忙解决一下，谢谢）