【SpringBoot】23 文件预览（kkFileView）

Gitee仓库

https://gitee.com/Lin_DH/system

介绍

文件预览功能是指在不打开或编辑文件的情况下，通过某种方式查看文件的内容、格式或者部分内容的功能。该功能通常用于文件管理系统、办公工具、在线教育平台、企业协作平台、电子邮件客户端等领域，能够提高用户体验，节省带宽和存储空间，并保护知识产权。
今天推荐一个用 SpringBoot 搭建的文档在线预览解决方案：kkFileView。

官网

https://kkfileview.keking.cn/zh-cn/index.html

运行项目

第一步：下载源码
https://github.com/kekingcn/kkFileView
在这里插入图片描述
第二步：用 IDEA 打开源码
第三步：配置 Maven

第四步：配置文件编码
第五步：配置编译环境

第六步：双击 Ctrl 键，输入打包命令：mvn package

打包获得 linux 环境运行的 kkFileView-x.x.x.tar.gz 和 window 环境运行的 kkFileView-x.x.x.zip，解压 .zip 文件获得 kkFileView-x.x.x 文件。
在这里插入图片描述
第七步：运行 kkFileView-x.x.x 文件中 bin 目录的 startup.bat 文件。

浏览器访问 http://127.0.0.1:8012/，成功运行项目访问到页面。

第八步：获取 base64 cdn
https://www.jsdelivr.com/package/npm/js-base64
三种调用方式
1）普通文件下载url预览

<script type="text/javascript"src="https://cdn.jsdelivr.net/npm/js-base64@3.6.0/base64.min.js"></script>
varurl = 'http://127.0.0.1:8080/file/test_.txt'; //要预览文件的访问地址 
window.open('http://127.0.0.1:8012/onlinePreview?url='+encodeURIComponent(Base64.encode(url)));

2）http / https下载流 url 预览

<script type="text/javascript"src="https://cdn.jsdelivr.net/npm/js-base64@3.6.0/base64.min.js"></script>
varoriginUrl = 'http://127.0.0.1:8080/filedownload?fileId=1'; //要预览文件的访问地址 
varpreviewUrl = originUrl + '&fullfilename=test.txt';
window.open('http://127.0.0.1:8012/onlinePreview?url='+encodeURIComponent(Base64.encode(previewUrl)));

3）FTP方式

<script type="text/javascript"src="https://cdn.jsdelivr.net/npm/js-base64@3.6.0/base64.min.js"></script>
varurl = 'ftp://127.0.0.1/file/test.txt'; //要预览文件的访问地址 
window.open('http://127.0.0.1:8012/onlinePreview?url='+encodeURIComponent(Base64.encode(url)));

第九步：配置静态文件位置

application.yml

spring:
    mvc:
      static-path-pattern: /static/**

在 resources 目录下，新建 static 目录，image 目录，并放入文件。
在这里插入图片描述
第十步：放入 js-base64 文件
在 static 目录下，新建 js 目录，放入 js-base64-v3.6.0.js 文件。

js-base64-v3.6.0.js


//
// THIS FILE IS AUTOMATICALLY GENERATED! DO NOT EDIT BY HAND!
//
;(function(global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined'
        ? module.exports = factory()
        : typeof define === 'function' && define.amd
        ? define(factory) :
        // cf. https://github.com/dankogai/js-base64/issues/119
        (function() {
            // existing version for noConflict()
            const _Base64 = global.Base64;
            const gBase64 = factory();
            gBase64.noConflict = () => {
                global.Base64 = _Base64;
                return gBase64;
            };
            if (global.Meteor) { // Meteor.js
                Base64 = gBase64;
            }
            global.Base64 = gBase64;
        })();
}((typeof self !== 'undefined' ? self
        : typeof window !== 'undefined' ? window
        : typeof global !== 'undefined' ? global
        : this
), function() {
    'use strict';

/**
 *  base64.ts
 *
 *  Licensed under the BSD 3-Clause License.
 *    http://opensource.org/licenses/BSD-3-Clause
 *
 *  References:
 *    http://en.wikipedia.org/wiki/Base64
 *
 * @author Dan Kogai (https://github.com/dankogai)
 */
const version = '3.6.0';
/**
 * @deprecated use lowercase `version`.
 */
const VERSION = version;
const _hasatob = typeof atob === 'function';
const _hasbtoa = typeof btoa === 'function';
const _hasBuffer = typeof Buffer === 'function';
const _TD = typeof TextDecoder === 'function' ? new TextDecoder() : undefined;
const _TE = typeof TextEncoder === 'function' ? new TextEncoder() : undefined;
const b64ch = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
const b64chs = [...b64ch];
const b64tab = ((a) => {
    let tab = {};
    a.forEach((c, i) => tab[c] = i);
    return tab;
})(b64chs);
const b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
const _fromCC = String.fromCharCode.bind(String);
const _U8Afrom = typeof Uint8Array.from === 'function'
    ? Uint8Array.from.bind(Uint8Array)
    : (it, fn = (x) => x) => new Uint8Array(Array.prototype.slice.call(it, 0).map(fn));
const _mkUriSafe = (src) => src
    .replace(/[+\/]/g, (m0) => m0 == '+' ? '-' : '_')
    .replace(/=+$/m, '');
const _tidyB64 = (s) => s.replace(/[^A-Za-z0-9\+\/]/g, '');
/**
 * polyfill version of `btoa`
 */
const btoaPolyfill = (bin) => {
    // console.log('polyfilled');
    let u32, c0, c1, c2, asc = '';
    const pad = bin.length % 3;
    for (let i = 0; i < bin.length;) {
        if ((c0 = bin.charCodeAt(i++)) > 255 ||
            (c1 = bin.charCodeAt(i++)) > 255 ||
            (c2 = bin.charCodeAt(i++)) > 255)
            throw new TypeError('invalid character found');
        u32 = (c0 << 16) | (c1 << 8) | c2;
        asc += b64chs[u32 >> 18 & 63]
            + b64chs[u32 >> 12 & 63]
            + b64chs[u32 >> 6 & 63]
            + b64chs[u32 & 63];
    }
    return pad ? asc.slice(0, pad - 3) + "===".substring(pad) : asc;
};
/**
 * does what `window.btoa` of web browsers do.
 * @param {String} bin binary string
 * @returns {string} Base64-encoded string
 */
const _btoa = _hasbtoa ? (bin) => btoa(bin)
    : _hasBuffer ? (bin) => Buffer.from(bin, 'binary').toString('base64')
        : btoaPolyfill;
const _fromUint8Array = _hasBuffer
    ? (u8a) => Buffer.from(u8a).toString('base64')
    : (u8a) => {
        // cf. https://stackoverflow.com/questions/12710001/how-to-convert-uint8-array-to-base64-encoded-string/12713326#12713326
        const maxargs = 0x1000;
        let strs = [];
        for (let i = 0, l = u8a.length; i < l; i += maxargs) {
            strs.push(_fromCC.apply(null, u8a.subarray(i, i + maxargs)));
        }
        return _btoa(strs.join(''));
    };
/**
 * converts a Uint8Array to a Base64 string.
 * @param {boolean} [urlsafe] URL-and-filename-safe a la RFC4648 §5
 * @returns {string} Base64 string
 */
const fromUint8Array = (u8a, urlsafe = false) => urlsafe ? _mkUriSafe(_fromUint8Array(u8a)) : _fromUint8Array(u8a);
// This trick is found broken https://github.com/dankogai/js-base64/issues/130
// const utob = (src: string) => unescape(encodeURIComponent(src));
// reverting good old fationed regexp
const cb_utob = (c) => {
    if (c.length < 2) {
        var cc = c.charCodeAt(0);
        return cc < 0x80 ? c
            : cc < 0x800 ? (_fromCC(0xc0 | (cc >>> 6))
                + _fromCC(0x80 | (cc & 0x3f)))
                : (_fromCC(0xe0 | ((cc >>> 12) & 0x0f))
                    + _fromCC(0x80 | ((cc >>> 6) & 0x3f))
                    + _fromCC(0x80 | (cc & 0x3f)));
    }
    else {
        var cc = 0x10000
            + (c.charCodeAt(0) - 0xD800) * 0x400
            + (c.charCodeAt(1) - 0xDC00);
        return (_fromCC(0xf0 | ((cc >>> 18) & 0x07))
            + _fromCC(0x80 | ((cc >>> 12) & 0x3f))
            + _fromCC(0x80 | ((cc >>> 6) & 0x3f))
            + _fromCC(0x80 | (cc & 0x3f)));
    }
};
const re_utob = /[\uD800-\uDBFF][\uDC00-\uDFFFF]|[^\x00-\x7F]/g;
/**
 * @deprecated should have been internal use only.
 * @param {string} src UTF-8 string
 * @returns {string} UTF-16 string
 */
const utob = (u) => u.replace(re_utob, cb_utob);
//
const _encode = _hasBuffer
    ? (s) => Buffer.from(s, 'utf8').toString('base64')
    : _TE
        ? (s) => _fromUint8Array(_TE.encode(s))
        : (s) => _btoa(utob(s));
/**
 * converts a UTF-8-encoded string to a Base64 string.
 * @param {boolean} [urlsafe] if `true` make the result URL-safe
 * @returns {string} Base64 string
 */
const encode = (src, urlsafe = false) => urlsafe
    ? _mkUriSafe(_encode(src))
    : _encode(src);
/**
 * converts a UTF-8-encoded string to URL-safe Base64 RFC4648 §5.
 * @returns {string} Base64 string
 */
const encodeURI = (src) => encode(src, true);
// This trick is found broken https://github.com/dankogai/js-base64/issues/130
// const btou = (src: string) => decodeURIComponent(escape(src));
// reverting good old fationed regexp
const re_btou = /[\xC0-\xDF][\x80-\xBF]|[\xE0-\xEF][\x80-\xBF]{2}|[\xF0-\xF7][\x80-\xBF]{3}/g;
const cb_btou = (cccc) => {
    switch (cccc.length) {
        case 4:
            var cp = ((0x07 & cccc.charCodeAt(0)) << 18)
                | ((0x3f & cccc.charCodeAt(1)) << 12)
                | ((0x3f & cccc.charCodeAt(2)) << 6)
                | (0x3f & cccc.charCodeAt(3)), offset = cp - 0x10000;
            return (_fromCC((offset >>> 10) + 0xD800)
                + _fromCC((offset & 0x3FF) + 0xDC00));
        case 3:
            return _fromCC(((0x0f & cccc.charCodeAt(0)) << 12)
                | ((0x3f & cccc.charCodeAt(1)) << 6)
                | (0x3f & cccc.charCodeAt(2)));
        default:
            return _fromCC(((0x1f & cccc.charCodeAt(0)) << 6)
                | (0x3f & cccc.charCodeAt(1)));
    }
};
/**
 * @deprecated should have been internal use only.
 * @param {string} src UTF-16 string
 * @returns {string} UTF-8 string
 */
const btou = (b) => b.replace(re_btou, cb_btou);
/**
 * polyfill version of `atob`
 */
const atobPolyfill = (asc) => {
    // console.log('polyfilled');
    asc = asc.replace(/\s+/g, '');
    if (!b64re.test(asc))
        throw new TypeError('malformed base64.');
    asc += '=='.slice(2 - (asc.length & 3));
    let u24, bin = '', r1, r2;
    for (let i = 0; i < asc.length;) {
        u24 = b64tab[asc.charAt(i++)] << 18
            | b64tab[asc.charAt(i++)] << 12
            | (r1 = b64tab[asc.charAt(i++)]) << 6
            | (r2 = b64tab[asc.charAt(i++)]);
        bin += r1 === 64 ? _fromCC(u24 >> 16 & 255)
            : r2 === 64 ? _fromCC(u24 >> 16 & 255, u24 >> 8 & 255)
                : _fromCC(u24 >> 16 & 255, u24 >> 8 & 255, u24 & 255);
    }
    return bin;
};
/**
 * does what `window.atob` of web browsers do.
 * @param {String} asc Base64-encoded string
 * @returns {string} binary string
 */
const _atob = _hasatob ? (asc) => atob(_tidyB64(asc))
    : _hasBuffer ? (asc) => Buffer.from(asc, 'base64').toString('binary')
        : atobPolyfill;
//
const _toUint8Array = _hasBuffer
    ? (a) => _U8Afrom(Buffer.from(a, 'base64'))
    : (a) => _U8Afrom(_atob(a), c => c.charCodeAt(0));
/**
 * converts a Base64 string to a Uint8Array.
 */
const toUint8Array = (a) => _toUint8Array(_unURI(a));
//
const _decode = _hasBuffer
    ? (a) => Buffer.from(a, 'base64').toString('utf8')
    : _TD
        ? (a) => _TD.decode(_toUint8Array(a))
        : (a) => btou(_atob(a));
const _unURI = (a) => _tidyB64(a.replace(/[-_]/g, (m0) => m0 == '-' ? '+' : '/'));
/**
 * converts a Base64 string to a UTF-8 string.
 * @param {String} src Base64 string.  Both normal and URL-safe are supported
 * @returns {string} UTF-8 string
 */
const decode = (src) => _decode(_unURI(src));
/**
 * check if a value is a valid Base64 string
 * @param {String} src a value to check
  */
const isValid = (src) => {
    if (typeof src !== 'string')
        return false;
    const s = src.replace(/\s+/g, '').replace(/=+$/, '');
    return !/[^\s0-9a-zA-Z\+/]/.test(s) || !/[^\s0-9a-zA-Z\-_]/.test(s);
};
//
const _noEnum = (v) => {
    return {
        value: v, enumerable: false, writable: true, configurable: true
    };
};
/**
 * extend String.prototype with relevant methods
 */
const extendString = function () {
    const _add = (name, body) => Object.defineProperty(String.prototype, name, _noEnum(body));
    _add('fromBase64', function () { return decode(this); });
    _add('toBase64', function (urlsafe) { return encode(this, urlsafe); });
    _add('toBase64URI', function () { return encode(this, true); });
    _add('toBase64URL', function () { return encode(this, true); });
    _add('toUint8Array', function () { return toUint8Array(this); });
};
/**
 * extend Uint8Array.prototype with relevant methods
 */
const extendUint8Array = function () {
    const _add = (name, body) => Object.defineProperty(Uint8Array.prototype, name, _noEnum(body));
    _add('toBase64', function (urlsafe) { return fromUint8Array(this, urlsafe); });
    _add('toBase64URI', function () { return fromUint8Array(this, true); });
    _add('toBase64URL', function () { return fromUint8Array(this, true); });
};
/**
 * extend Builtin prototypes with relevant methods
 */
const extendBuiltins = () => {
    extendString();
    extendUint8Array();
};
const gBase64 = {
    version: version,
    VERSION: VERSION,
    atob: _atob,
    atobPolyfill: atobPolyfill,
    btoa: _btoa,
    btoaPolyfill: btoaPolyfill,
    fromBase64: decode,
    toBase64: encode,
    encode: encode,
    encodeURI: encodeURI,
    encodeURL: encodeURI,
    utob: utob,
    btou: btou,
    decode: decode,
    isValid: isValid,
    fromUint8Array: fromUint8Array,
    toUint8Array: toUint8Array,
    extendString: extendString,
    extendUint8Array: extendUint8Array,
    extendBuiltins: extendBuiltins,
};

    //
    // export Base64 to the namespace
    //
    // ES5 is yet to have Object.assign() that may make transpilers unhappy.
    // gBase64.Base64 = Object.assign({}, gBase64);
    gBase64.Base64 = {};
    Object.keys(gBase64).forEach(k => gBase64.Base64[k] = gBase64[k]);
    return gBase64;
}));

第十一步：编写文件预览页面

filePreview.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head lang="en">
    <meta charset="UTF-8" />
    <title>文件预览页面</title>
    <script type="text/javascript" th:src="@{../static/js/js-base64-v3.6.0.js}"></script>
</head>

<body>
<h1>文件预览页面</h1>
<button th:onclick="'previewFile();'">预览</button>
</body>

<script th:inline="javascript">
    function previewFile () {
        const domain = "http://127.0.0.1";
        const fileUrl = domain + ":8888/static/image/Avatar.jpg";
        //const fileUrl = domain + ":8888/static/js/js-base64-v3.6.0.js";
        const url = domain + ":8012/onlinePreview?url=" + encodeURIComponent(Base64.encode(fileUrl));
        window.open(url);
    }
</script>

</html>

第十二步：编写文件访问类

FileController.java

/**
 * @author DUHAOLIN
 * @date 2024/10/15
 */
@Controller
public class FileController {
    
    @GetMapping("filePreview")
    public String filePreview() {
        return "filePreview";
    }

}