MySQL 直接存储图片并在 html 页面中展示，点击下载

数据库实体类：

package com.easy.kotlin.picturecrawler.entity

import java.util.*
import javax.persistence.*

@Entity
@Table(indexes = arrayOf(
        Index(name = "idx_url", unique = true, columnList = "url"),
        Index(name = "idx_category", unique = false, columnList = "category")))
class Image {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    var id: Long = -1
    @Version
    var version: Int = 0

    @Column(length = 255, unique = true, nullable = false)
    var category: String = ""
    var isFavorite: Int = 0

    @Column(length = 255, unique = true, nullable = false)
    var url: String = ""

    var gmtCreated: Date = Date()
    var gmtModified: Date = Date()
    var isDeleted: Int = 0  //1 Yes 0 No
    var deletedDate: Date = Date()

    @Lob
    var imageBlob: ByteArray = byteArrayOf()
    /* 0-Baidu  1-Gank */
    var sourceType: Int = 0

    override fun toString(): String {
        return "Image(id=$id, version=$version, category='$category', isFavorite=$isFavorite, url='$url', gmtCreated=$gmtCreated, gmtModified=$gmtModified, isDeleted=$isDeleted, deletedDate=$deletedDate)"
    }
}

其中的 @Lob  var imageBlob: ByteArray = byteArrayOf() 这个字段存储图片的 Base64内容。

存库代码

                val Image = Image()
                Image.category = "干货集中营福利"
                Image.url = url
                Image.sourceType = 1
                Image.imageBlob = getByteArray(url)
                logger.info("Image = ${Image}")
                imageRepository.save(Image)

其中的getByteArray(url) 函数：

    private fun getByteArray(url: String): ByteArray {
        val urlObj = URL(url)
        return urlObj.readBytes()
    }

前端 html 展示图片代码：

{
        title: '图片',
        field: 'imageBlob',
        align: 'center',
        valign: 'middle',
        formatter: function (value, row, index) {
            // var html = "<img onclick=downloadImage('" + value + "') width='100%' src='" + value + "'>"
            var html = '<img onclick="downBase64Image(this.src)" width="100%" src="data:image/jpg;base64,' + value + '"/>'
            return html
        }
    }

点击下载 js ：

function downloadImage(src) {
    var $a = $("<a></a>").attr("href", src).attr("download", "sotu.png");
    $a[0].click();
}


function downBase64Image(url) {
    var blob = base64Img2Blob(url);
    url = window.URL.createObjectURL(blob);
    var $a = $("<a></a>").attr("href", url).attr("download", "sotu.png");
    $a[0].click();
}


function base64Img2Blob(code) {
    var parts = code.split(';base64,');
    var contentType = parts[0].split(':')[1];
    var raw = window.atob(parts[1]);
    var rawLength = raw.length;

    var uInt8Array = new Uint8Array(rawLength);

    for (var i = 0; i < rawLength; ++i) {
        uInt8Array[i] = raw.charCodeAt(i);
    }

    return new Blob([uInt8Array], {type: contentType});
}

或者：

function downloadFile(fileName, content) {
    var aLink = document.createElement('a');
    var blob = base64Img2Blob(content); //new Blob([content]);
    var evt = document.createEvent("HTMLEvents");
    evt.initEvent("click", false, false);//initEvent 不加后两个参数在FF下会报错
    aLink.download = fileName;
    aLink.href = URL.createObjectURL(blob);
    aLink.dispatchEvent(evt);
}