小小吐槽

接到一个小小需求，在pc端和手机端展现pdf，要求是完美展现pdf，pdf不能让用户下载，网上很多pdf的，我这里pc端用的是
iframe，在pc端没有问题，然后到了手机端如果是pdf文件就直接跳到下载去了，无法实现我的效果，手机端采用的是pdfjs-dist(强烈建议)，在这期间我还用了其他的方法（具体的忘记了）反正效果没有实现，展现了pdf，但是效果不是很好(k可能是我当时没有看懂其他实现pdf的方法)，我这里强烈建议pdfjs-dist

安装 pdfjs-dist

npm install --save pdfjs-dist@2.0.943

vue代码实现（图片展示）

<template>
  <div class="main-container">
    <input type="file" ref="fielinput" @change="uploadFile" />
    <button @click="previous">测试</button>
    <div class="canvas-container">
      <canvas ref="myCanvas" class="pdf-container"> </canvas>
    </div>
    <div class="pagination-wrapper">
      <button @click="clickPre">上一页</button>
      <span>第{{ pageNo }} / {{ pdfPageNumber }}页</span>
      <button @click="clickNext">下一页</button>
    </div>
  </div>
</template>

<script>
import * as pdfJS from 'pdfjs-dist';
//这里的文件在踩坑目录下，注意看下
import { getUint8Array } from "../baese64/getFile.js";


pdfJS.GlobalWorkerOptions.workerSrc = pdfJS;
export default {
  mounted() {},
  data() {
    return {
      pageNo: null,
      pdfPageNumber: null,
      pdfTotalPages: 1,
      renderingPage: false,
      pdfData: null, // PDF的base64
      scale: 1, // 缩放值
    };
  },
  methods: {
    //这个是我本地测试将文件转换为base64
    uploadFile() {
      let inputDom = this.$refs.fielinput;
      console.log("inputDom",inputDom);
      let file = inputDom.files[0];
      let reader = new FileReader();
      reader.readAsDataURL(file);
      reader.onload = () => {
        let data = atob(
          reader.result.substring(reader.result.indexOf(",") + 1)
        );
        this.loadPdfData(data);
      };
    },
    previous() {
      // 请求参数
      this.$ajax
                .post("http://172.28.233.159:8081/getBase?fileName=" + "测试")
                .then((res) => {
                var data = getUint8Array(res.data.data);
                this.loadPdfData(data);
                });
    },
    loadPdfData(data) {
      // 引入pdf.js的字体，如果没有引用的话字体会不显示
      let CMAP_URL = "https://unpkg.com/pdfjs-dist@2.0.943/cmaps/";
      //读取base64的pdf流文件
      this.pdfData = pdfJS.getDocument({
        data: data, // PDF base64编码
        cMapUrl: CMAP_URL,
        cMapPacked: true,
      });
      console.log(this.pdfData);
      this.renderPage(1);
      this.renderScrollPdf();
    },


    // 根据页码渲染相应的PDF
    renderPage(num) {
      this.renderingPage = true;
      this.pdfData.promise.then((pdf) => {
        this.pdfPageNumber = pdf.numPages;

        pdf.getPage(num).then((page) => {
          // 获取DOM中为预览PDF准备好的canvasDOM对象
          let canvas = this.$refs.myCanvas;
          let viewport = page.getViewport(this.scale);
          canvas.height = viewport.height;
          canvas.width = viewport.width;

          let ctx = canvas.getContext("2d");
          let renderContext = {
            canvasContext: ctx,
            viewport: viewport,
          };
          page.render(renderContext).then(() => {
            this.renderingPage = false;
            this.pageNo = num;
          });
        });
      });
    },
    clickPre() {
      if (!this.renderingPage && this.pageNo && this.pageNo > 1) {
        this.renderPage(this.pageNo - 1);
      }
    },
    clickNext() {
      if (
        !this.renderingPage &&
        this.pdfPageNumber &&
        this.pageNo &&
        this.pageNo < this.pdfPageNumber
      ) {
        this.renderPage(this.pageNo + 1);
      }
    },
    renderScrollPdf() {
      this.pdfData.promise.then((pdf) => {
        this.pdfTotalPages = pdf.numPages;
        this.renderScrollPdfPage(1);
      });
    },
  },
};
</script>

<style scoped>
.main-container {
  display: flex;
  flex-direction: column;
  align-items: center;
}
.canvas-container {
  width: 400px;
  height: 500px;
  border: 1px dashed black;
  position: relative;
  display: flex;
  justify-content: center;
}
.scroll-pdf-contanier {
  width: 400px;
  height: 500px;
  border: 1px dashed black;
  position: relative;
  display: flex;
  flex-direction: column;
  overflow-y: scroll;
}
.pdf-container {
  width: 100%;
  height: 100%;
}
.scroll-pdf-container {
  width: 350px;
}
.pagination-wrapper {
  display: flex;
  justify-content: center;
  align-items: center;
}
</style>

PC 端点击测试

手机端点击测试

java将pdf转换为base64

JDK8

package com.java.util;


import sun.misc.BASE64Encoder;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;


public class PDFFileUtils {

    /**
     * 方法名:          PDFToBase64
     * 方法功能描述:     将pdf文件转换为Base64编码
     * @param:        String sourceFile:源文件路径
     * @return:       String  base64字符串
     * @Author:       Leiwen
     * @Create Date:   2022年12月03日
     */
    public static String PDFToBase64(String sourceFile) {
        BASE64Encoder encoder = new BASE64Encoder();
        FileInputStream fin =null;
        BufferedInputStream bin =null;
        ByteArrayOutputStream baos = null;
        BufferedOutputStream bout =null;
        File file = new File(sourceFile);
        try {
            fin = new FileInputStream(file);
            bin = new BufferedInputStream(fin);
            baos = new ByteArrayOutputStream();
            bout = new BufferedOutputStream(baos);
            byte[] buffer = new byte[1024];
            int len = bin.read(buffer);
            while(len != -1){
                bout.write(buffer, 0, len);
                len = bin.read(buffer);
            }
            //刷新此输出流并强制写出所有缓冲的输出字节
            bout.flush();
            byte[] bytes = baos.toByteArray();
            return encoder.encodeBuffer(bytes).trim();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                fin.close();
                bin.close();
                bout.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    public static String getImgUrlToBase64(String imgUrl) {
        InputStream inputStream = null;
        ByteArrayOutputStream outputStream = null;
        byte[] buffer = null;
        try {
            // 创建URL
            URL url = new URL(imgUrl);
            // 创建链接
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(5000);
            inputStream = conn.getInputStream();
            outputStream = new ByteArrayOutputStream();
            // 将内容读取内存中
            buffer = new byte[1024];
            int len = -1;
            while ((len = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, len);
            }
            buffer = outputStream.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (inputStream != null) {
                try {
                    // 关闭inputStream流
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (outputStream != null) {
                try {
                    // 关闭outputStream流
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        // 对字节数组Base64编码
        return new BASE64Encoder().encode(buffer);
    }




    public static void main(String[] args) {
//        String s = PDFToBase64("/Users/leiwen/Downloads/测试011.pdf");
//        System.out.println(s);

        String imgUrlToBase64 = getImgUrlToBase64("/Users/leiwen/Downloads/测试011.pdf");
        System.out.println(imgUrlToBase64);
    }
}

注意点
JDK如果是8的话能正常使用BASE64Encoder
JDK11的话这个就被弃用了，我另外一台电脑用的是11，用的maven资源 是如下，效果跟BASE64Encoder一样

        <dependency>
            <groupId>org.apache.directory.studio</groupId>
            <artifactId>org.apache.commons.codec</artifactId>
            <version>1.8</version>
        </dependency>

JDK11

package com.java.util;


import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;
import org.apache.commons.codec.binary.Base64;


public class PDFFileUtils {

    /**
     * 方法名:          PDFToBase64
     * 方法功能描述:     将pdf文件转换为Base64编码
     * @param:        String sourceFile:源文件路径
     * @return:       String  base64字符串
     * @Author:       Leiwen
     * @Create Date:   2022年11月09日
     */
    public static String PDFToBase64(String sourceFile) {
        Base64 encoder = new Base64();
        FileInputStream fin =null;
        BufferedInputStream bin =null;
        ByteArrayOutputStream baos = null;
        BufferedOutputStream bout =null;
        File file = new File(sourceFile);
        try {
            fin = new FileInputStream(file);
            bin = new BufferedInputStream(fin);
            baos = new ByteArrayOutputStream();
            bout = new BufferedOutputStream(baos);
            byte[] buffer = new byte[1024];
            int len = bin.read(buffer);
            while(len != -1){
                bout.write(buffer, 0, len);
                len = bin.read(buffer);
            }
            //刷新此输出流并强制写出所有缓冲的输出字节
            bout.flush();
            byte[] bytes = baos.toByteArray();
            return encoder.encodeBase64String(bytes).trim();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                fin.close();
                bin.close();
                bout.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    public static void main(String[] args) {
//        String s = PDFToBase64("/Users/leiwen/Downloads/测试011.pdf");
//        System.out.println(s);

    }
}

踩坑

我一开始的思路是将后台的base64转给前端，然后转成文件，再转换成base64，因为前台的文件转base64再转pdf能够实现，然后我后台转的再前台转换失败，好像是因为文件在后台转换的base64和文件在前台转换的base64有一协议啥的，转换不了

   /**
   * 简介：将base64 格式的字符串转换成 uint8Array （pdf.js 无法直接接受base64 格式的参数）
   * 参数：base64_string(pdf格式的电子发票经过base64处理的字符串)
   * return：Array
   */

  export const  getUint8Array = (base64Str) =>{
    let data = base64Str.replace(/[\n\r]/g, '');  // 替换多余的空格和换行
    var raw = window.atob(data);
    var rawLength = raw.length;
          var array = new Uint8Array(new ArrayBuffer(rawLength));
          for (var i = 0; i < rawLength; i++) {
              array[i] = raw.charCodeAt(i)
          }
      return array
}