文件上传和下载

要想实现文件上传和下载，其实只需要下述代码即可：

文件上传和下载

import cn.hutool.core.io.FileUtil;
import cn.hutool.core.util.StrUtil;
import com.example.common.Result;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;import javax.servlet.http.HttpServletResponse;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.List;/***  文件上传下载接口*/
@RestController
@RequestMapping("/files")
public class FileController {// 文件上传存储路径private static final String filePath = System.getProperty("user.dir") + "/file/";/*** 文件上传** @param file 待上传的文件* @return 返回上传文件的标识符*/@PostMapping("/upload")public Result upload(MultipartFile file) {synchronized (FileController.class) {// 生成唯一标识符，避免文件覆盖String flag = System.currentTimeMillis() + ""; //当前时间戳String fileName = file.getOriginalFilename(); //文件原始名称try {// 确保文件存储目录存在if (!FileUtil.isDirectory(filePath)) {FileUtil.mkdir(filePath);}// 文件存储形式：时间戳-文件名FileUtil.writeBytes(file.getBytes(), filePath + flag + "-" + fileName);System.out.println(fileName + "--上传成功");Thread.sleep(1L);} catch (Exception e) {System.err.println(fileName + "--文件上传失败");}// 返回文件标识符return Result.success(flag);//返回的是时间戳【数据库中存储的也是那个时间戳】相当于唯一的ID}}/*** 获取文件** @param flag 文件的标识符* @param response 用于返回文件流*/@GetMapping("/{flag}") //根据时间戳public void avatarPath(@PathVariable String flag, HttpServletResponse response) {// 确保文件存储目录存在if (!FileUtil.isDirectory(filePath)) {FileUtil.mkdir(filePath);}OutputStream os;List<String> fileNames = FileUtil.listFileNames(filePath);// 根据标识符查找对应的文件名String avatar = fileNames.stream().filter(name -> name.contains(flag)).findAny().orElse("");try {if (StrUtil.isNotEmpty(avatar)) {// 设置返回的文件名response.addHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(avatar, "UTF-8"));response.setContentType("application/octet-stream");// 读取文件内容并返回byte[] bytes = FileUtil.readBytes(filePath + avatar);os = response.getOutputStream();os.write(bytes);os.flush();os.close();}} catch (Exception e) {System.out.println("文件下载失败");}}}

上述代码，算是固定写法！！可以用来上传图片，文件等资源！

拿走不谢！！

---

只用来看文件上传下载其实没啥意思！小编是在图书信息管理的基础上来进行图片封面的上传的！

相关代码：

图书信息管理的增删改查

1. 创建数据库表

CREATE TABLE `book` (`id` int(10) NOT NULL AUTO_INCREMENT COMMENT '主键ID',`name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '图书名称',`price` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '图书价格',`author` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '图书作者',`press` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '图书出版社',`img` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '图书封面',PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

1. 创建实体类Book.java

@Table(name = "book")
public class Book {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Integer id;@Column(name = "name")private String name;@Column(name = "price")private String price;@Column(name = "author")private String author;@Column(name = "press")private String press;@Column(name = "img")private String img;
}

1. BookDao.java BookMapper.xml

import com.example.entity.Book;
import com.example.entity.Params;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Repository;
import tk.mybatis.mapper.common.Mapper;import java.util.List;@Repository
public interface BookDao extends Mapper<Book> {List<Book> findBySearch(@Param("params") Params params);
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.dao.BookDao"><select id="findBySearch" resultType="com.example.entity.Book">select * from book<where><if test="params != null and params.name != null and params.name != ''">and name like concat('%', #{ params.name }, '%')</if><if test="params != null and params.author != null and params.author != ''">and author like concat('%', #{ params.author }, '%')</if></where></select></mapper>

1. BookService.java

import com.example.dao.BookDao;
import com.example.entity.Book;
import com.example.entity.Params;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import org.springframework.stereotype.Service;import javax.annotation.Resource;
import java.util.List;@Service
public class BookService {@Resourceprivate BookDao bookDao;public PageInfo<Book> findBySearch(Params params) {// 开启分页查询PageHelper.startPage(params.getPageNum(), params.getPageSize());// 接下来的查询会自动按照当前开启的分页设置来查询List<Book> list = bookDao.findBySearch(params);return PageInfo.of(list);}public void add(Book book) {bookDao.insertSelective(book);}public void update(Book book) {bookDao.updateByPrimaryKeySelective(book);}public void delete(Integer id) {bookDao.deleteByPrimaryKey(id);}
}

1. BookController.java

import com.example.common.Result;
import com.example.entity.Book;
import com.example.entity.Params;
import com.example.service.BookService;
import com.github.pagehelper.PageInfo;
import org.springframework.web.bind.annotation.*;import javax.annotation.Resource;@CrossOrigin
@RestController
@RequestMapping("/book")
public class BookController {@Resourceprivate BookService bookService;@GetMapping("/search")public Result findBySearch(Params params) {PageInfo<Book> info = bookService.findBySearch(params);return Result.success(info);}@PostMappingpublic Result save(@RequestBody Book book) {if (book.getId() == null) {bookService.add(book);} else {bookService.update(book);}return Result.success();}@DeleteMapping("/{id}")public Result delete(@PathVariable Integer id) {bookService.delete(id);return Result.success();}}

图书封面文件上传

1. FileController.java

1. 上传下载接口不能拦截，需要放行

jwt令牌拦截器那块内容

// 加自定义拦截器JwtInterceptor，设置拦截规则
@Override
public void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(jwtInterceptor).addPathPatterns("/api/**").excludePathPatterns("/api/files/**").excludePathPatterns("/api/admin/login").excludePathPatterns("/api/admin/register");
}

1. BookView.vue

el-upload：Element - The world's most popular Vue UI framework

<el-form-item label="图书封面" label-width="20%"><el-upload action="http://localhost:8080/api/files/upload" :on-success="successUpload"><el-button size="small" type="primary">点击上传</el-button></el-upload>
</el-form-item>

successUpload(res) {this.form.img = res.data;
},

图书封面预览、下载

el-image：Element - The world's most popular Vue UI framework

<el-table-column label="图书封面"><template v-slot="scope"><el-imagestyle="width: 70px; height: 70px; border-radius: 50%":src="'http://localhost:8080/api/files/' + scope.row.img":preview-src-list="['http://localhost:8080/api/files/' + scope.row.img]"></el-image></template>
</el-table-column><el-button type="primary" @click="down(scope.row.img)">下载</el-button>

down(flag) {location.href = 'http://localhost:8080/api/files/' + flag
}

恭喜你，看到了最后，浪费了你一俩分钟时间，其实下面的图书信息管理的增删改查都是废话内容，最重要的就是上面的文件上传和下载，但是你还是看下去了！感谢你的信赖！