前言

近期我正在开发一个前后端分离项目，使用了Spring Boot 和 Vue2，借助了国内优秀的框架 jeecg，前端UI库则选择了 ant-design-vue。在项目中，需要实现文件上传功能，同时还要能够在线预览和下载图片和PDF文件，甚至需要在页面上直接打印PDF文件。尽管框架自带了 vue-print-nb-jeecg 组件，但它相对较为简陋，只支持单页打印，无法实现多页打印。经过仔细的权衡和比较后，最终决定采用 vue-pdf 和 print-js 组件来满足需求。

一、先来展示一下最终效果

前端上传文件列表：

点击PDF文件后展示预览：

点击打印按钮后效果：

二、实现步骤及代码

vue-pdf 可以用于在线预览，而 print-js 则提供了更强大的打印功能，支持多种文档类型，包括PDF、HTML、IMAGE和JSON，而且默认情况下是PDF。其实vue-pdf 也可以实现打印功能，但是跟前述的vue-print-nb一样，只能打印页面显示的第一页内容（预览展示没问题）。
Print.js官网👉点我直达

1. 在vue中安装vue-pdf 和Print.js

yarn add vue-pdf
...
yarn add print-js

2. 可以全局引入，也可以在需要的文件中引入

 import pdf from 'vue-pdf'
 import printJS from 'print-js'

3.主要代码

<a-modal :visible="previewVisibleForAll" :footer="null" @cancel="handleCancelAll" :width="800" :maskClosable="maskClosable" :keyboard="keyboard">
     <img alt="example" style="width: 100%;margin-top:20px" :src="previewFileSrc" v-if="isImage"/>

     <div v-if="isPdf" style="overflow-y: auto;overflow-x: hidden;">
       <a-button shape="round" icon="file-pdf" @click="handlePrint(printData)" size="small">打印</a-button>
       <div id="printFrom">
         <pdf ref="pdf" v-for="item in pageTotal"
              :src="previewFileSrc"
              :key="item"
              :page="item"></pdf>
       </div>
     </div>

 </a-modal>

打印按钮执行的方法

// data参数
printData: {
  printable: 'printFrom',
  header: '',
  ignore: ['no-print']
},

// 执行方法
handlePrint(params) {
  printJS({
    printable: params.printable, // 'printFrom', // 标签元素id
    type: params.type || 'html',
    header: params.header, // '表单',
    targetStyles: ['*'],
    style: '@page {margin:0 10mm};', // 可选-打印时去掉眉页眉尾
    ignoreElements: params.ignore || [], // ['no-print']
    properties: params.properties || null
  })
}

不同组件，如果文件是图片就预览图片，PDF就预览PDF。

4. 全部代码：

<template>
  <div :id="containerId" style="position: relative">

    <!--  ---------------------------- begin 图片左右换位置 ------------------------------------- -->
    <div class="movety-container" :style="{top:top+'px',left:left+'px',display:moveDisplay}" style="padding:0 8px;position: absolute;z-index: 91;height: 32px;width: 104px;text-align: center;">
      <div :id="containerId+'-mover'" :class="showMoverTask?'uploadty-mover-mask':'movety-opt'" style="margin-top: 12px">
        <a @click="moveLast" style="margin: 0 5px;"><a-icon type="arrow-left" style="color: #fff;font-size: 16px"/></a>
        <a @click="moveNext" style="margin: 0 5px;"><a-icon type="arrow-right" style="color: #fff;font-size: 16px"/></a>
      </div>
    </div>
    <!--  ---------------------------- end 图片左右换位置 ------------------------------------- -->

    <a-upload
      name="file"
      :multiple="multiple"
      :action="uploadAction"
      :headers="headers"
      :data="{'biz':bizPath}"
      :fileList="fileList"
      :beforeUpload="doBeforeUpload"
      @change="handleChange"
      :disabled="disabled"
      :returnUrl="returnUrl"
      :listType="complistType"
      @preview="handlePreview1"
      :showUploadList="{
                showRemoveIcon: true,
                showDownloadIcon: true
              }"
      :class="{'uploadty-disabled':disabled}">
      <template>
        <div v-if="isImageComp">
          <a-icon type="plus" />
          <div class="ant-upload-text">{{ text }}</div>
        </div>
        <a-button v-else-if="buttonVisible">
         <a-icon type="upload" />{{ text }}
        </a-button>
      </template>
    </a-upload>
    <a-modal :visible="previewVisible" :footer="null" @cancel="handleCancel">
      <img alt="example" style="width: 100%" :src="previewImage" />
    </a-modal>
    <a-modal :visible="previewVisibleForAll" :footer="null" @cancel="handleCancelAll" :width="800" :maskClosable="maskClosable" :keyboard="keyboard">
      <img alt="example" style="width: 100%;margin-top:20px" :src="previewFileSrc" v-if="isImage"/>

      <div v-if="isPdf" style="overflow-y: auto;overflow-x: hidden;">
        <a-button shape="round" icon="file-pdf" @click="handlePrint(printData)" size="small">打印</a-button>
        <div id="printFrom">
          <pdf ref="pdf" v-for="item in pageTotal"
               :src="previewFileSrc"
               :key="item"
               :page="item"></pdf>
        </div>
      </div>

    </a-modal>
  </div>
</template>

<script>

  import Vue from 'vue'
  import { ACCESS_TOKEN } from "@/store/mutation-types"
  import { getFileAccessHttpUrl } from '@/api/manage';
  import pdf from 'vue-pdf'
  import printJS from 'print-js'
  const FILE_TYPE_ALL = "all"
  const FILE_TYPE_IMG = "image"
  const FILE_TYPE_TXT = "file"
  const uidGenerator=()=>{
    return '-'+parseInt(Math.random()*10000+1,10);
  }
  const getFileName=(path)=>{
    if(path.lastIndexOf("\\")>=0){
      let reg=new RegExp("\\\\","g");
      path = path.replace(reg,"/");
    }
    return path.substring(path.lastIndexOf("/")+1);
  }
  export default {
    name: 'JUpload',
    components: { pdf },
    data(){
      return {
        printData: {
          printable: 'printFrom',
          header: '',
          ignore: ['no-print']
        },
        uploadAction:window._CONFIG['domianURL']+"/sys/common/upload",
        headers:{},
        fileList: [],
        newFileList: [],
        uploadGoOn:true,
        previewVisible: false,
        //---------------------------- begin 图片左右换位置 -------------------------------------
        previewImage: '',
        containerId:'',
        top:'',
        left:'',
        moveDisplay:'none',
        showMoverTask:false,
        moverHold:false,
        currentImg:'',
        //---------------------------- end 图片左右换位置 -------------------------------------
        previewVisibleForAll:false,
        pageTotal: null,
        previewFileSrc:'',
        isImage:false,
        isExcel:false,
        isPdf:false,
      }
    },
    props:{
      text:{
        type:String,
        required:false,
        default:"点击上传"
      },
      fileType:{
        type:String,
        required:false,
        default:FILE_TYPE_ALL
      },
      /*这个属性用于控制文件上传的业务路径*/
      bizPath:{
        type:String,
        required:false,
        default:"temp"
      },
      value:{
        type:[String,Array],
        required:false
      },
      // update-begin- --- author:wangshuai ------ date:20190929 ---- for:Jupload组件增加是否能够点击
      disabled:{
        type:Boolean,
        required:false,
        default: false
      },
      // update-end- --- author:wangshuai ------ date:20190929 ---- for:Jupload组件增加是否能够点击
      //此属性被废弃了
      triggerChange:{
        type: Boolean,
        required: false,
        default: false
      },
      /**
       * update -- author:lvdandan -- date:20190219 -- for:Jupload组件增加是否返回url，
       * true：仅返回url
       * false：返回fileName filePath fileSize
       */
      returnUrl:{
        type:Boolean,
        required:false,
        default: true
      },
      number:{
        type:Number,
        required:false,
        default: 0
      },
      buttonVisible:{
        type:Boolean,
        required:false,
        default: true
      },
      multiple: {
        type: Boolean,
        default: true
      },
      beforeUpload: {
        type: Function
      },
      maskClosable: {
        type: Boolean,
        default:true,
      },
      keyboard: {
        type: Boolean,
        default:true,
      },
    },
    watch:{
      value:{
        immediate: true,
        handler() {
          let val = this.value
          if (val instanceof Array) {
            if(this.returnUrl){
              this.initFileList(val.join(','))
            }else{
              this.initFileListArr(val);
            }
          } else {
            this.initFileList(val)
          }
        }
      }
    },
    computed:{
      isImageComp(){
        return this.fileType === FILE_TYPE_IMG
      },
      complistType(){
        return this.fileType === FILE_TYPE_IMG?'picture-card':'text'
      }
    },
    created(){
      const token = Vue.ls.get(ACCESS_TOKEN);
      //---------------------------- begin 图片左右换位置 -------------------------------------
      this.headers = {"X-Access-Token":token};
      this.containerId = 'container-ty-'+new Date().getTime();
      //---------------------------- end 图片左右换位置 -------------------------------------
    },

    methods:{
      handlePrint(params) {
        printJS({
          printable: params.printable, // 'printFrom', // 标签元素id
          type: params.type || 'html',
          header: params.header, // '表单',
          targetStyles: ['*'],
          style: '@page {margin:0 10mm};', // 可选-打印时去掉眉页眉尾
          ignoreElements: params.ignore || [], // ['no-print']
          properties: params.properties || null
        })
      },
      printPdf() {
        this.$refs.pdf.print()
        // window.print()
      },
      initFileListArr(val){
        console.log(val)
        if(!val || val.length==0){
          this.fileList = [];
          return;
        }
        let fileList = [];
        for(var a=0;a<val.length;a++){
          let url = getFileAccessHttpUrl(val[a].filePath);
          fileList.push({
            uid:uidGenerator(),
            name:val[a].fileName,
            status: 'done',
            url: url,
            response:{
              status:"history",
              message:val[a].filePath
            }
          })
        }
        this.fileList = fileList
        console.log(this.fileList)
      },
      initFileList(paths){
        if(!paths || paths.length==0){
          //return [];
          // update-begin- --- author:os_chengtgen ------ date:20190729 ---- for:issues:326,Jupload组件初始化bug
          this.fileList = [];
          return;
          // update-end- --- author:os_chengtgen ------ date:20190729 ---- for:issues:326,Jupload组件初始化bug
        }
        let fileList = [];
        let arr = paths.split(",")
        for(var a=0;a<arr.length;a++){
          let url = getFileAccessHttpUrl(arr[a]);
          fileList.push({
            uid:uidGenerator(),
            name:getFileName(arr[a]),
            status: 'done',
            url: url,
            response:{
              status:"history",
              message:arr[a]
            }
          })
        }
        this.fileList = fileList
      },
      handlePathChange(){
        let uploadFiles = this.fileList
        let path = ''
        if(!uploadFiles || uploadFiles.length==0){
          path = ''
        }
        let arr = [];

        for(var a=0;a<uploadFiles.length;a++){
          // update-begin-author:lvdandan date:20200603 for:【TESTA-514】【开源issue】多个文件同时上传时，控制台报错
          if(uploadFiles[a].status === 'done' ) {
            arr.push(uploadFiles[a].response.message)
          }else{
            return;
          }
          // update-end-author:lvdandan date:20200603 for:【TESTA-514】【开源issue】多个文件同时上传时，控制台报错
        }
        if(arr.length>0){
          path = arr.join(",")
        }
        this.$emit('change', path);
      },
      doBeforeUpload(file){
        this.uploadGoOn=true
        var fileType = file.type;
        if(this.fileType===FILE_TYPE_IMG){
          if(fileType.indexOf('image')<0){
            this.$message.warning('请上传图片');
            this.uploadGoOn=false
            return false;
          }
        }
        // 文件大小限定在600K以下
        const isLt2M = file.size / 1024 / 1024 < 10;
        if (!isLt2M){
            this.$message.warning('请确保上传的文件小于10MB！');
          this.fileList = []
            this.uploadGoOn=false
            return false;
        }
        // 扩展 beforeUpload 验证
        if (typeof this.beforeUpload === 'function') {
          return this.beforeUpload(file)
        }
        return true
      },
      handleChange(info) {
        console.log("--文件列表改变--")
        if(!info.file.status && this.uploadGoOn === false){
          info.fileList.pop();
        }
        let fileList = info.fileList
        if(info.file.status==='done'){
          if(this.number>0){
            fileList = fileList.slice(-this.number);
          }
          if(info.file.response.success){
            fileList = fileList.map((file) => {
              if (file.response) {
                let reUrl = file.response.message;
                file.url = getFileAccessHttpUrl(reUrl);
              }
              return file;
            });
          }
          //this.$message.success(`${info.file.name} 上传成功!`);
        }else if (info.file.status === 'error') {
          this.$message.error(`${info.file.name} 上传失败.`);
        }else if(info.file.status === 'removed'){
          this.handleDelete(info.file)
        }
        this.fileList = fileList
        if(info.file.status==='done' || info.file.status === 'removed'){
          //returnUrl为true时仅返回文件路径
          if(this.returnUrl){
            this.handlePathChange()
          }else{
            //returnUrl为false时返回文件名称、文件路径及文件大小
            this.newFileList = [];
            for(var a=0;a<fileList.length;a++){
              // update-begin-author:lvdandan date:20200603 for:【TESTA-514】【开源issue】多个文件同时上传时，控制台报错
              if(fileList[a].status === 'done' ) {
                var fileJson = {
                  fileName:fileList[a].name,
                  filePath:fileList[a].response.message,
                  fileSize:fileList[a].size
                };
                this.newFileList.push(fileJson);
              }else{
                return;
              }
              // update-end-author:lvdandan date:20200603 for:【TESTA-514】【开源issue】多个文件同时上传时，控制台报错
            }
            this.$emit('change', this.newFileList);
          }
        }
      },
      handleDelete(file){
        //如有需要新增 删除逻辑
        console.log(file)
      },
      // handlePreview(file){
      //   console.log('file')
      //   console.log(file)
      //   if(this.fileType === FILE_TYPE_IMG){
      //     this.previewImage = file.url || file.thumbUrl;
      //     this.previewVisible = true;
      //   }else{
      //     if(file.name.endsWith('pdf') || file.name.endsWith('PDF')) {
      //       let viewPath = window._CONFIG['domianURL'].replace('9999', '15550').replace('/jeecg-boot', '') + '/' + (file.url.replace(window._CONFIG['staticDomainURL'] + "/", ''))
      //       console.log(viewPath)
      //       window.open(viewPath,"_blank")
      //     this.isPdf = true
      //       this.previewFileSrc = file.url
      //     }
      //     // else {//TODO:重新打开页面
      //     //   location.href=file.url
      //     // }
      //   }
      // },
      // 获取pdf总页数
      getTotal() {
        // 多页pdf的src中不能直接使用后端获取的pdf地址 否则会按页数请求多次数据
        // 需要使用下述方法的返回值作为url
        this.previewFileSrc = pdf.createLoadingTask(this.previewFileSrc)
        // 获取页码
        this.previewFileSrc.promise.then(pdf => this.pageTotal = pdf.numPages).catch(error => {
        })
      },
      handlePreview1(file){
        if(this.fileType === FILE_TYPE_IMG){
          this.previewImage = file.url || file.thumbUrl;
          this.previewVisible = true;
        }else{
          // 判断当前文件类型
          this.previewFileSrc = file.url || file.thumbUrl; // "http://localhost:9999/sys/common/static/orderPaymentInfo/网约区域复习题_1694585302732.pdf"
          let fileTypeLocal = this.matchFileType(file.name);
          this.isImage = false;
          this.isPdf = false;
          if(fileTypeLocal == 'image') {
            this.previewVisibleForAll = true;
            this.isImage = true;
          } else if(fileTypeLocal == 'pdf') {
            this.previewVisibleForAll = true;
            this.isPdf = true;
            this.getTotal()
          } else {
            location.href=file.url
          }
        }
      },
      matchFileType(fileName) {
        // 后缀获取
        let suffix = '';
        // 获取类型结果
        let result = '';
        if (!fileName) return false;
        try {
          // 截取文件后缀
          suffix = fileName.substr(fileName.lastIndexOf('.') + 1, fileName.length)
          // 文件后缀转小写，方便匹配
          suffix = suffix.toLowerCase()
        } catch (err) {
          suffix = '';
        }
        // fileName无后缀返回 false
        if (!suffix) {
          result = false;
          return result;
        }

        let fileTypeList = [
          // 图片类型
          {'typeName': 'image', 'types': ['png', 'jpg', 'jpeg', 'bmp', 'gif']},
          // 文本类型
          {'typeName': 'txt', 'types': ['txt']},
          // excel类型
          {'typeName': 'excel', 'types': ['xls', 'xlsx']},
          {'typeName': 'word', 'types': ['doc', 'docx']},
          {'typeName': 'pdf', 'types': ['pdf']},
          {'typeName': 'ppt', 'types': ['ppt']},
          // 视频类型
          {'typeName': 'video', 'types': ['mp4', 'm2v', 'mkv']},
          // 音频
          {'typeName': 'radio', 'types': ['mp3', 'wav', 'wmv']}
        ]
        // let fileTypeList = ['image', 'txt', 'excel', 'word', 'pdf', 'video', 'radio']
        for (let i = 0; i < fileTypeList.length; i++) {
          const fileTypeItem = fileTypeList[i]
          const typeName = fileTypeItem.typeName
          const types = fileTypeItem.types
          console.log(fileTypeItem);
          result = types.some(function (item) {
            return item === suffix;
          });
          if (result) {
            return typeName
          }
        }
        return 'other'
      },
      handleCancel(){
        this.previewVisible = false;
      },
      handleCancelAll(){
        this.previewVisibleForAll = false;
        this.isImage = false;
        this.isPdf = false;
      },
      //---------------------------- begin 图片左右换位置 -------------------------------------
      moveLast(){
        //console.log(ev)
        //console.log(this.fileList)
        //console.log(this.currentImg)
        let index = this.getIndexByUrl();
        if(index==0){
          this.$message.warn('未知的操作')
        }else{
          let curr = this.fileList[index].url;
          let last = this.fileList[index-1].url;
          let arr =[]
          for(let i=0;i<this.fileList.length;i++){
            if(i==index-1){
              arr.push(curr)
            }else if(i==index){
              arr.push(last)
            }else{
              arr.push(this.fileList[i].url)
            }
          }
          this.currentImg = last
          this.$emit('change',arr.join(','))
        }
      },
      moveNext(){
        let index = this.getIndexByUrl();
        if(index==this.fileList.length-1){
          this.$message.warn('已到最后~')
        }else{
          let curr = this.fileList[index].url;
          let next = this.fileList[index+1].url;
          let arr =[]
          for(let i=0;i<this.fileList.length;i++){
            if(i==index+1){
              arr.push(curr)
            }else if(i==index){
              arr.push(next)
            }else{
              arr.push(this.fileList[i].url)
            }
          }
          this.currentImg = next
          this.$emit('change',arr.join(','))
        }
      },
      getIndexByUrl(){
        for(let i=0;i<this.fileList.length;i++){
          if(this.fileList[i].url === this.currentImg || encodeURI(this.fileList[i].url) === this.currentImg){
            return i;
          }
        }
        return -1;
      }
    },
    mounted(){
      const moverObj = document.getElementById(this.containerId+'-mover');
      if(moverObj){
        moverObj.addEventListener('mouseover',()=>{
          this.moverHold = true
          this.moveDisplay = 'block';
        });
        moverObj.addEventListener('mouseout',()=>{
          this.moverHold = false
          this.moveDisplay = 'none';
        });
      }
    
      let picList = document.getElementById(this.containerId)?document.getElementById(this.containerId).getElementsByClassName('ant-upload-list-picture-card'):[];
      if(picList && picList.length>0){
        picList[0].addEventListener('mouseover',(ev)=>{
          ev = ev || window.event;
          let target = ev.target || ev.srcElement;
          if('ant-upload-list-item-info' == target.className){
            this.showMoverTask=false
            let item = target.parentElement
            this.left = item.offsetLeft
            this.top=item.offsetTop+item.offsetHeight-50;
            this.moveDisplay = 'block';
            this.currentImg = target.getElementsByTagName('img')[0].src
          }

        });

        picList[0].addEventListener('mouseout',(ev)=>{
          ev = ev || window.event;
          let target = ev.target || ev.srcElement;
          //console.log('移除',target)
          if('ant-upload-list-item-info' == target.className){
            this.showMoverTask=true
            setTimeout(()=>{
              if(this.moverHold === false)
                this.moveDisplay = 'none';
            },100)
          }
          if('ant-upload-list-item ant-upload-list-item-done' == target.className || 'ant-upload-list ant-upload-list-picture-card'== target.className){
            this.moveDisplay = 'none';
          }
        })
        //---------------------------- end 图片左右换位置 -------------------------------------
      }
    },
    model: {
      prop: 'value',
      event: 'change'
    }
  }
</script>

<style lang="less">
.uploadty-disabled{
  .ant-upload-list-item {
    .anticon-close{
      display: none;
    }
    .anticon-delete{
      display: none;
    }
  }
}
  //---------------------------- begin 图片左右换位置 -------------------------------------
  .uploadty-mover-mask{
    background-color: rgba(0, 0, 0, 0.5);
    opacity: .8;
    color: #fff;
    height: 28px;
    line-height: 28px;
  }
  //---------------------------- end 图片左右换位置 -------------------------------------
</style>

总结

除了以上两个组件库1+1的方式，还有百度前端大神开发的vue-office组件库，而且优点也很明显：

• 使用简单，对新手友好，只传递一个文件地址，就可实现预览。
• 提供多种文件的一站式预览解决方案，解决常见的docx、excel、pdf三种文件的预览。
• 预览效果也好，不只是对内容预览，也要支持样式。

预览的效果确实超级棒，可惜的是不支持打印功能，不能满足需求，可惜了。
有需要的可以去看vue-office的演示效果：
Vue框架演示效果
非Vue框架文件预览