图片对象列表查询与展示（vue+springboot+elementUI）

本文描述场景为
展示：后端从数据库中查询图片对象列表，返回前端展示

多图片展示

先看一下后端表实体

import com.zpmc.common.domain.BaseEntity;
import io.swagger.annotations.ApiModel;
import lombok.*;

import javax.persistence.*;
import java.io.Serializable;
import java.sql.Blob;

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Builder
@ApiModel
@Entity
@Table(name = "tb_image")
public class Image extends BaseEntity implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "task_id")
    private Integer taskId;

    @Column(name = "directory", length = 200)
    private String directory;


    @Column(name = "file")
    private Blob file;

    @Column(name = "remark", length = 200)
    private String remark;

    @Column(name = "STATUS", length = 200)
    private Integer status;

}

显然，图片在数据库中使用的是Blob类型,本人数据库用的是MediumBlob。

MySQL的四种BLOB类型
类型 大小(单位：字节)
TinyBlob 最大 255
Blob 最大 65K
MediumBlob 最大 16M
LongBlob 最大 4G

思路

1. Blob属性先转成字节数组
2. 字节数组转成base64字符串
3. 前端接收base64解析展示

当然，后端返回给前端，还差个VO,因为Blob类型没法传。

后端

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class ImageVO {
    private static final long serialVersionUID = 1L;
    private Integer id;
    private Integer taskId;
    private String directory;
    private String file;
    private String remark;
    private Integer status;
}

Controller层

    @ApiOperation("查看图片列表")
    @GetMapping("getImageList")
    public Result getImageList() throws Exception {
        return imageService.getImageList();
    }

Service层

    @Override
    public Result getImageList() throws SQLException {
        List<ImageVO> voList=new ArrayList<>();
        List<Image> all = imageRepo.findAll();
        for (Image item : all) {
            ImageVO vo = new ImageVO();
            vo.setId(item.getId());
            vo.setDirectory(item.getDirectory());
            vo.setRemark(item.getRemark());
            vo.setStatus(item.getStatus());
            vo.setTaskId(item.getTaskId());
            Blob blob = item.getFile();
            // 将 Blob 数据转换为字节数组
            byte[] data = blob.getBytes(1, (int) blob.length());
            // 将字节数组转换为 Base64 编码字符串
            vo.setFile(Base64.getEncoder().encodeToString(data));
            voList.add(vo);
        }
        return Result.success(voList);
    }

前端

<div v-for="image in images" :key="image.id" style="display: inline-block;">
          <el-image class="selectEffect" :src="image.file" :fit="fit" alt="加载失败" :title="image.id" style="width: 200px; height: 200px; margin-right: 10px;cursor: pointer;"
            @click="handleImageClick(image)">
          el-image>
          <div>
            <center>
              {{ image.id }}
              
              <input type="checkbox" v-model="selectedImages" :value="image">
            center>
          div>

  data() {
    return {
      fit: "fill",
      selectedImages: [],
      images: [],
    };
  },
    beforeDestroy() {
    // 在组件销毁前，释放URL对象
    // URL.revokeObjectURL(this.image);
    for (let i = 0; i < this.images.length; i++) {
      URL.revokeObjectURL(this.images[i].file);
    }
  },
    methods: {
    getImageList() {
      Image.getImageList()
        .then((res) => {
          let arr = res.data;
          for (let i = 0; i < arr.length; i++) {
            arr[i].file = "data:image/png;base64," + arr[i].file;
          }
          this.images = arr;
          console.log("---------------");
          console.log(this.images);
          console.log("---------------");
        })
        .catch((err) => {
          console.log("err", err);
        });
    }
   }