NIO单文件上传

用到的依赖(这些不是必须的，只是为了方便调试使用)

<dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.6.1</version>
        </dependency>

        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.6.1</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

package com.xx.demo;

import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

@RestController
@Slf4j
@Api(value = "测试文件上传")
public class Test {

    final String path = "G:\\images\\";

    @PostMapping("/oneFileUpload")
    @ApiOperation(value = "测试单文件上传接口")
    public String oneFileUpload (MultipartFile file, String username, String password) throws IOException {

        log.info(username + "," + password);

        // 判断文件是否为空
        if(file == null){
            log.info("文件不能为空");
            return "文件不能为空";
        }else{
            // 获取文件名
            String fileName = file.getOriginalFilename();
            // 获取文件后缀名
            String suffixName = fileName.substring(fileName.lastIndexOf(".") + 1);
            // 获取文件类型,校验文件的合法性
            String contentType = file.getContentType();
            if(contentType.contains("image")){
                log.info("上传的文件是图片");
                // 设置文件存储路径,使用新的文件名,避免文件名冲突
                String finalPath = this.path + System.currentTimeMillis() + "." + suffixName;
                Path path = Paths.get(finalPath);
                Files.write(path, file.getBytes());
                return "文件上传成功";
            }else{
                log.info("上传的文件不是图片");
                return "文件类型不是图片";
            }
        }
    }
}