前后端分离使用Spring Boot + el-upload 完成图片上传

前端环境配置

从Element文档找见upload对应的代码先copy下来，这里选择的是用户头像上传中的代码。然后要替换一下action中的接口地址，换成自己后端的，这里我的后端地址为http://localhost:5277/api/article/UploadPic

修改一下handleAvatarSuccess方法
这里提一嘴，如果你的项目中请求的时候需要携带token，那么要在upload中加上:headers="headers属性，把token赋值给headers。

 handleAvatarSuccess(res, file) {console.log(res);this.imageUrl = res.data;console.log("图片预览的url:"+this.imageUrl);}

前端整体代码如下：

<template><el-uploadclass="avatar-uploader"action="http://localhost:5277/api/article/UploadPic":show-file-list="false":on-success="handleAvatarSuccess":before-upload="beforeAvatarUpload":headers="headers"><img v-if="imageUrl" :src="data:imageUrl" class="avatar" /><i v-else class="el-icon-plus avatar-uploader-icon"></i></el-upload>
</template><style>
.avatar-uploader .el-upload {border: 1px dashed #d9d9d9;border-radius: 6px;cursor: pointer;position: relative;overflow: hidden;
}
.avatar-uploader .el-upload:hover {border-color: #409eff;
}
.avatar-uploader-icon {font-size: 28px;color: #8c939d;width: 178px;height: 178px;line-height: 178px;text-align: center;
}
.avatar {width: 178px;height: 178px;display: block;
}
</style><script>
import { getToken } from "@/utils/auth"; // get token from cookie
export default {data() {return {imageUrl: "",headers: {token: getToken() ? getToken() : "",},};},methods: {handleAvatarSuccess(res, file) {console.log(res);this.imageUrl = res.data;console.log("图片预览的url:"+this.imageUrl);},beforeAvatarUpload(file) {const isJPG = file.type === "image/jpeg";const isLt2M = file.size / 1024 / 1024 < 2;if (!isJPG) {this.$message.error("上传头像图片只能是 JPG 格式!");}if (!isLt2M) {this.$message.error("上传头像图片大小不能超过 2MB!");}return isJPG && isLt2M;},},
};
</script>

文件auth.js中的getToken()方法为

import Cookies from 'js-cookie'const TokenKey = 'Admin-Token'export function getToken() {return Cookies.get(TokenKey)
}

搭建后端环境

可以参考之前的一篇文章，用IDEA快速搭建SpringBoot环境，这里搭建环境不做重点介绍。搭建完环境以后，引入上传文件的依赖

     <!--文件上传--><dependency><groupId>commons-fileupload</groupId><artifactId>commons-fileupload</artifactId><version>1.4</version></dependency>

这里要重点说明一下，浏览器只能访问resources/static下的文件，之后把图片存到里面才可以直接访问。这里在static下再新建一个img文件夹专门用于存放图片。

如果这个img文件夹直接放在resource下是访问不到的，会报404的错误。文件会上传到target/classes/static/img目录下

之后访问的时候直接使用端口号+/img(如http://localhost:5277/img/2022-04-97/154b20d9-32de-43b7-997e-50e925a8becc.png)即可访问到，访问链接中不需要再img之前再加static/,否则也会报404的错误。

     //返回可供外界访问的urlString url = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + "/img" + format + newName;

之后建立Controller文件

import com.cms.utils.ResultUtils;
import com.cms.utils.ResultVo;
import org.springframework.util.ResourceUtils;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;@RestController
@RequestMapping("/api/article")
public class ImgController {@PostMapping("/UploadPic")public ResultVo UploadPic(MultipartFile file, HttpServletRequest request) throws FileNotFoundException {SimpleDateFormat dateFormat = new SimpleDateFormat("/yyyy-MM-DD/");String filename = file.getOriginalFilename();//取得文件名称if (!filename.endsWith(".png") && !filename.endsWith(".jpg")) {return ResultUtils.error("文件类型不对");}String format = dateFormat.format(new Date());//realPath为文件保存的位置String realPath = ResourceUtils.getURL("classpath:").getPath() + "static/img" + format;realPath = realPath.substring(1);//去掉第一个/符号File folder = new File(realPath);if (!folder.exists()) {folder.mkdirs();}String newName;if (filename.endsWith(".png"))newName = UUID.randomUUID().toString() + ".png";elsenewName = UUID.randomUUID().toString() + ".jpg";try {//新建文件file.transferTo(new File(folder, newName));//String url = realPath + newName;} catch (IOException e) {return ResultUtils.error(e.getMessage());}//返回可供外界访问的urlString url = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + "/img" + format + newName;return ResultUtils.success("图片上传成功", url);}
}

注：这里ResultUtils和ResultVo是我自定义的两个类

ResultUtils:

/*** 数据返回工具类*/
public class ResultUtils {/*** 无参数返回* @return*/public static ResultVo success() {return Vo(null, StatusCode.SUCCESS_CODE, null);}public static ResultVo success(String msg){return Vo(msg,StatusCode.SUCCESS_CODE,null);}/*** 返回带参数* @param msg* @param data* @return*/public static ResultVo success(String msg,Object data){return Vo(msg,StatusCode.SUCCESS_CODE,data);}public static ResultVo success(String msg,int code,Object data){return Vo(msg,code,data);}public static ResultVo Vo(String msg, int code, Object data) {return new ResultVo(msg, code, data);}/*** 错误返回* @return*/public static ResultVo error(){return Vo(null,StatusCode.ERROR_CODE,null);}public static ResultVo error(String msg){return Vo(msg,StatusCode.ERROR_CODE,null);}public static ResultVo error(String msg,int code,Object data){return Vo(msg,code,data);}public static ResultVo error(String msg,int code){return Vo(msg,code,null);}public static ResultVo error(String msg,Object data){return Vo(msg, StatusCode.ERROR_CODE,data);}
}

ResultVo:

public class ResultVo<T> {private String msg;private int code;private T data;
}

这样就上传成功了

注：如果项目中加入了Spring Security，要对图片访问链接进行放行。
再次感谢一位神秘计科大佬鼎力相助~