springboot上传图片到本地或者阿里云服务器，然后本地访问或者外网访问的步骤

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * @author zhangjiahao
 */
@Configuration
public class WebMvcConfig  implements WebMvcConfigurer {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        /**
         * 资源映射路径
         * addResourceHandler：访问映射路径
         * addResourceLocations：资源绝对路径
         */
        registry.addResourceHandler("/upload/**").addResourceLocations("file:D:/upload/");
    }
}

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * @author zhangjiahao
 * @date 2020/1/10 16:04
 */
@Configuration
public class LoginConfig implements WebMvcConfigurer {

    @Bean
    public InterceptorConfig interceptorConfig(){
        return new InterceptorConfig();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //注册TestInterceptor拦截器
        InterceptorRegistration  registration= registry.addInterceptor(new InterceptorConfig());
        registration.addPathPatterns("/**");                      //所有路径都被拦截
        registration.excludePathPatterns(                         //添加不拦截路径
                "/***",            //登录
                "/upload/**"            //图片
        );
    }
}

@RequestMapping(value = "/upload", method = RequestMethod.POST)
    public String upload(@RequestParam(value = "file") MultipartFile file) throws IOException {
        // 获取文件名
        String fileName = file.getOriginalFilename();
        // 获取文件的后缀名
        String suffixName = fileName.substring(fileName.lastIndexOf("."));
        List<String> extList = Arrays.asList(".jpg", ".png", ".jpeg", ".gif");
        if (!extList.contains(suffixName)) {
            return "图片格式非法";
        }
        // 解决中文问题，liunx下中文路径，图片显示问题
        fileName = UUID.randomUUID().toString().replace("-", "") + suffixName;
        // 返回客户端 文件地址 URL
         String url = "localhost:8080"+"/upload/" + fileName;
        File dest = new File( uploadDir + fileName);
        // 检测是否存在目录
        if (!dest.getParentFile().exists()) {
            dest.getParentFile().mkdirs();
        }
        file.transferTo(dest);
        return url;
    }

   @RequestMapping(value = "/uploadBase64", method = RequestMethod.POST)
    public Object upload(@RequestParam String image) throws IOException {
        try {
        // image格式: "data:image/png;base64," + "图片的base64字符串"
            MultipartFile multipartFile = Base64Util.base64ToMultipart(image);
            String originalFilename = multipartFile.getOriginalFilename();
            // 文件扩展名
            String ext = originalFilename.substring(originalFilename.lastIndexOf(".")).trim();
            List<String> extList = Arrays.asList(".jpg", ".png", ".jpeg", ".gif");
            if (!extList.contains(ext)) {
                return new BaseResult(HttpStatus.INTERNAL_SERVER_ERROR,"图片格式非法");
            }
            String randomFilename = UUID.randomUUID().toString().replace("-", "") + ext;
            //将文件写入服务器
            String fileLocalPath = uploadDir + randomFilename;
            File localFile = new File(fileLocalPath);
            multipartFile.transferTo(localFile);
            InetAddress address = InetAddress.getLocalHost();
            //写入服务器成功后组装返回的数据格式
            return new BaseResult(HttpStatus.OK,address.getHostAddress()+":8080/upload/" + randomFilename);
        } catch (Exception e) {
            logger.error("上传图片失败：", e);
        }
        return new BaseResult(HttpStatus.INTERNAL_SERVER_ERROR);
    }

import lombok.extern.slf4j.Slf4j;
import org.springframework.web.multipart.MultipartFile;
import sun.misc.BASE64Decoder;

import java.io.IOException;

/**
 * @author zhangjiahao
 */
@Slf4j
public class Base64Util {

    public static MultipartFile base64ToMultipart(String base64) {
        try {
            String[] baseStr = base64.split(",");

            BASE64Decoder decoder = new BASE64Decoder();
            byte[] b = new byte[0];
            b = decoder.decodeBuffer(baseStr[1]);

            for(int i = 0; i < b.length; ++i) {
                if (b[i] < 0) {
                    b[i] += 256;
                }
            }

            return new BASE64DecodedMultipartFile(b, baseStr[0]);
        } catch (IOException e) {
            log.error(e.getMessage());
            return null;
        }
    }
}

import org.springframework.web.multipart.MultipartFile;

import java.io.*;

/**
 * 自定义的MultipartFile的实现类，主要用于base64上传文件，以下方法都可以根据实际项目自行实现
 *
 * @author zhangjiahao
 */
public class BASE64DecodedMultipartFile implements MultipartFile {

    private final byte[] imgContent;
    private final String header;

    public BASE64DecodedMultipartFile(byte[] imgContent, String header) {
        this.imgContent = imgContent;
        this.header = header.split(";")[0];
    }

    @Override
    public String getName() {
        return System.currentTimeMillis() + Math.random() + "." + header.split("/")[1];
    }

    @Override
    public String getOriginalFilename() {
        return System.currentTimeMillis() + (int) Math.random() * 10000 + "." + header.split("/")[1];
    }

    @Override
    public String getContentType() {
        return header.split(":")[1];
    }

    @Override
    public boolean isEmpty() {
        return imgContent == null || imgContent.length == 0;
    }

    @Override
    public long getSize() {
        return imgContent.length;
    }

    @Override
    public byte[] getBytes() throws IOException {
        return imgContent;
    }

    @Override
    public InputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(imgContent);
    }

    @Override
    public void transferTo(File dest) throws IOException, IllegalStateException {
        new FileOutputStream(dest).write(imgContent);
    }
}