PAS/src/main/java/cn/cslg/pas/common/CyCacheUtil.java

package cn.cslg.pas.common;

import cn.cslg.pas.common.utils.StringUtils;
import org.apache.commons.codec.binary.Base64;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.ImageType;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Component;

import javax.imageio.ImageIO;
import java.awt.image.RenderedImage;
import java.io.*;

/**
 * 缓存类，该类中定义一些用于缓存的方法
 *
 * @author chenyu
 * @date 2023/9/15
 */
@Component
public class CyCacheUtil implements Serializable {

    /**
     * 缓存指定专利号的说明书pdf首页的图片数据
     *
     * @param patentNo 专利号
     * @param pdfFile  pdf文件
     * @return 返回该专利号的说明书pdf首页的图片数据
     */
    @Cacheable(cacheNames = "imgData", key = "#patentNo")
    public String getImgData(String patentNo, File pdfFile) throws IOException {
        //pdf转图片方式二（用依赖pdfbox）
        PDDocument doc = PDDocument.load(pdfFile);
        String newFilePath = StringUtils.getUUID() + ".pdf";
        File outputFile = new File(newFilePath);
        PDFRenderer pdfRenderer = new PDFRenderer(doc);
        // 提取的页码
        int pageNumber = 0;
        // 以300 dpi 读取存入 BufferedImage 对象
        int dpi = 300;
        RenderedImage buffImage = pdfRenderer.renderImageWithDPI(pageNumber, dpi, ImageType.RGB);
        // 将 BufferedImage 写入到 png
        ImageIO.write(buffImage, "png", outputFile);
        doc.close();
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        FileInputStream in = new FileInputStream(outputFile);
        int bytesRead;
        byte[] buffer = new byte[8192];

        //读取pdf首页临时文件
        while ((bytesRead = in.read(buffer)) != -1) {
            out.write(buffer, 0, bytesRead);
        }
        //关闭读取流
        in.close();
        byte[] bytes = out.toByteArray();
        String imgData = Base64.encodeBase64String(bytes);
        //关闭写出流
        out.close();
        //最后记得删除pdf首页的临时文件
        new File(newFilePath).delete();
        return imgData;
    }

    @CacheEvict(cacheNames = "imgData", key = "#patentNo")
    public void deleteImgData(String patentNo) {
        //在名称为imgData的缓存中删除key为该专利号的缓存内容（即删除该专利号的说明书pdf首页的图片数据）
    }

}