Java实现PDF在线预览

前言：之前一直PDF一直是下载后再查看，一直在想如何如何在线预览，现已找到方法，作此笔记，也希望都对其他人有所帮助

代码实现

@Slf4j
@Controller
@RequestMapping("/file/view")
public class FileViewController {


     /**
     * 预览pdf
     * @param request
     * @param response
     */
    @GetMapping("/pdf")
    public void preViewPDF(HttpServletRequest request, HttpServletResponse response) {
        String pdfFilePath = request.getParameter("fileName");
        String replace = pdfFilePath.replace('_', File.separatorChar);
        try (
                FileInputStream inputStream = new FileInputStream(replace);
                OutputStream outputStream = response.getOutputStream()
        ) {
            File pdfFile = new File(pdfFilePath);
            String suffix = FileUtil.getSuffix(pdfFile); // 获取文件后缀
            MimeTypeEnum mimeTypeEnum = MimeTypeEnum.findByExtension(suffix);
            if (mimeTypeEnum == null) {
                throw new FileException(101, "该文件类型不支持预览");
            }
            response.setContentType(mimeTypeEnum.getMimeType());
            IOUtils.write(IOUtils.toByteArray(inputStream), outputStream);
        } catch (FileNotFoundException e) {
            log.error("pdf路径不存在", e);
        } catch (IOException e) {
            log.error("写入出现IO异常", e);
        }
    }

 @GetMapping("/pdf_base64")
    @ResponseBody
    public String htmlViewPDF(String pdfFilePath){
        String base64 = "";
        String replace = pdfFilePath.replace('_', File.separatorChar);
        try (FileInputStream inputStream = new FileInputStream(replace)){
            byte[] data = IOUtils.toByteArray(inputStream);
            base64 = Base64Utils.encodeToString(data);
            base64 = base64.replaceAll("\r\n",""); // 去除空格和换行替换
            base64 = base64.replaceAll("\\+","%2B"); // 对base64中的”+“进行转义
            base64 = "data:application/pdf;base64," + base64;
        } catch (FileNotFoundException e) {
            log.error("pdf路径不存在", e);
        } catch (IOException e) {
            log.error("写入出现IO异常", e);
        }
        return base64;
    }

@Getter
@NoArgsConstructor
@AllArgsConstructor
public enum MimeTypeEnum {

    AAC("acc","AAC音频","audio/aac"),

    ABW("abw","AbiWord文件","application/x-abiword"),

    ARC("arc","存档文件","application/x-freearc"),

    AVI("avi","音频视频交错格式","video/x-msvideo"),

    AZW("azw","亚马逊Kindle电子书格式","application/vnd.amazon.ebook"),

    BIN("bin","任何类型的二进制数据","application/octet-stream"),

    BMP("bmp","Windows OS / 2位图图形","image/bmp"),

    BZ("bz","BZip存档","application/x-bzip"),

    BZ2("bz2","BZip2存档","application/x-bzip2"),

    CSH("csh","C-Shell脚本","application/x-csh"),

    CSS("css","级联样式表（CSS）","text/css"),

    CSV("csv","逗号分隔值（CSV）","text/csv"),

    DOC("doc","微软Word文件","application/msword"),

    DOCX("docx","Microsoft Word（OpenXML）","application/vnd.openxmlformats-officedocument.wordprocessingml.document"),

    EOT("eot","MS Embedded OpenType字体","application/vnd.ms-fontobject"),

    EPUB("epub","电子出版物（EPUB）","application/epub+zip"),

    GZ("gz","GZip压缩档案","application/gzip"),

    GIF("gif","图形交换格式（GIF）","image/gif"),

    HTM("htm","超文本标记语言（HTML）","text/html"),

    HTML("html","超文本标记语言（HTML）","text/html"),

    ICO("ico","图标格式","image/vnd.microsoft.icon"),

    ICS("ics","iCalendar格式","text/calendar"),

    JAR("jar","Java存档","application/java-archive"),

    JPEG("jpeg","JPEG图像","image/jpeg"),

    JPG("jpg","JPEG图像","image/jpeg"),

    JS("js","JavaScript","text/javascript"),

    JSON("json","JSON格式","application/json"),

    JSONLD("jsonld","JSON-LD格式","application/ld+json"),

    MID("mid","乐器数字接口（MIDI）","audio/midi"),

    MIDI("midi","乐器数字接口（MIDI）","audio/midi"),

    MJS("mjs","JavaScript模块","text/javascript"),

    MP3("mp3","MP3音频","audio/mpeg"),

    MPEG("mpeg","MPEG视频","video/mpeg"),

    MPKG("mpkg","苹果安装程序包","application/vnd.apple.installer+xml"),

    ODP("odp","OpenDocument演示文稿文档","application/vnd.oasis.opendocument.presentation"),

    ODS("ods","OpenDocument电子表格文档","application/vnd.oasis.opendocument.spreadsheet"),

    ODT("odt","OpenDocument文字文件","application/vnd.oasis.opendocument.text"),

    OGA("oga","OGG音讯","audio/ogg"),

    OGV("ogv","OGG视频","video/ogg"),

    OGX("ogx","OGG","application/ogg"),

    OPUS("opus","OPUS音频","audio/opus"),

    OTF("otf","otf字体","font/otf"),

    PNG("png","便携式网络图形","image/png"),

    PDF("pdf","Adobe 可移植文档格式（PDF）","application/pdf"),

    PHP("php","php","application/x-httpd-php"),

    PPT("ppt","Microsoft PowerPoint","application/vnd.ms-powerpoint"),

    PPTX("pptx","Microsoft PowerPoint（OpenXML）","application/vnd.openxmlformats-officedocument.presentationml.presentation"),

    RAR("rar","RAR档案","application/vnd.rar"),

    RTF("rtf","富文本格式","application/rtf"),

    SH("sh","Bourne Shell脚本","application/x-sh"),

    SVG("svg","可缩放矢量图形（SVG）","image/svg+xml"),

    SWF("swf","小型Web格式（SWF）或Adobe Flash文档","application/x-shockwave-flash"),

    TAR("tar","磁带存档（TAR）","application/x-tar"),

    TIF("tif","标记图像文件格式（TIFF）","image/tiff"),

    TIFF("tiff","标记图像文件格式（TIFF）","image/tiff"),

    TS("ts","MPEG传输流","video/mp2t"),

    TTF("ttf","ttf字体","font/ttf"),

    TXT("txt","文本（通常为ASCII或ISO 8859- n","text/plain"),

    VSD("vsd","微软Visio","application/vnd.visio"),

    WAV("wav","波形音频格式","audio/wav"),

    WEBA("weba","WEBM音频","audio/webm"),

    WEBM("webm","WEBM视频","video/webm"),

    WEBP("webp","WEBP图像","image/webp"),

    WOFF("woff","Web开放字体格式（WOFF）","font/woff"),

    WOFF2("woff2","Web开放字体格式（WOFF）","font/woff2"),

    XHTML("xhtml","XHTML","application/xhtml+xml"),

    XLS("xls","微软Excel","application/vnd.ms-excel"),

    XLSX("xlsx","微软Excel（OpenXML）","application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"),

    XML("xml","XML","application/xml"),

    XUL("xul","XUL","application/vnd.mozilla.xul+xml"),

    ZIP("zip","ZIP","application/zip"),

    MIME_3GP("3gp", "3GPP audio/video container", "video/3gpp"),

    MIME_3GP_WITHOUT_VIDEO("3gp", "3GPP audio/video container doesn't contain video", "audio/3gpp2"),

    MIME_3G2("3g2", "3GPP2 audio/video container", "video/3gpp2"),

    MIME_3G2_WITHOUT_VIDEO("3g2", "3GPP2 audio/video container  doesn't contain video", "audio/3gpp2"),

    MIME_7Z("7z","7-zip存档","application/x-7z-compressed")
    ;

    private String extension;

    private String explain;

    private String mimeType;



    public static MimeTypeEnum findByExtension(String extension) {
        if(StringUtils.isBlank(extension)){
            return null;
        }
        for (MimeTypeEnum typesEnum : MimeTypeEnum.values()) {
            if (extension.equals(typesEnum.getExtension())) {
                return typesEnum;
            }
        }
        return null;
    }

    public static String getContentType(String fileType) {
        MimeTypeEnum mimeTypeEnum = MimeTypeEnum.findByExtension(fileType);
        if(mimeTypeEnum != null){
            return mimeTypeEnum.getMimeType();
        }
        return "application/octet-stream";
    }

}

同理，图片也可以使用这种方法进行实现

提示：fileName这个参数是你服务器上存储PDF的文件地址
修改：之前的代码流没有关掉，现在修改了，然后如果你的pdf文件如果是保存在服务器上，这个fileName这个字段就是你服务器上存储PDF的文件地址，当然也可以做些处理，比如加密啥的，只要能保证解析到这个pdf文件就行，最后这个是预览pdf的地址，如果有需求要预览连接的，就自己在写业务需求的时候把这个连接拼接一下就行了，然后返回给前端
因为有时候需要pdf在页面嵌入展示，因此这边增加了一个可以在页面嵌入展示的方法，原理就是将pdf转为base64的格式，方便页面展示