在最近的一个项目中，遇到一个非常棘手的性能问题，场景是这样的：有PC端和手机端两个应用，用户在PC端上传的附件，如word,Excel,pdf等，当用户出差或不在电脑边上时，上传的附件在手机端能够打开预览。然后问题就来了，当在PC端上传的附件比较大，在手机端想要预览就比较慢，有时候甚至打不开，怎么解决这个性能问题呢？
一、多线程分段下载
分析：在预览的时候，将原文件切分成多分，使用多线程分段下载，这种方案可以快速的下载一个大文件到本地，然后直接打开预览，但是用户不同意将附件下载到手机上，因为手机内存有限，几个大附件就把内存占满了。
二、生成静态HTML文件
分析：在PC端上传附件的时候，启用异步线程，借助aspose组件，将附件转成成静态HTML文件，并放在单独的一个Tomcat下面，手机端预览附件的时候，直接访问这个Tomcat中的静态HTML，这样大大提升了预览速度，还不会占用手机内存，上传及预览的逻辑如下
转静态资源时，需要aspose组件的支持，因此需要在pom.xml中引入aspoxe相关组件
<dependency><groupId>aspose</groupId><artifactId>aspose.pdf</artifactId><version>17.2.0</version></dependency><dependency><groupId>aspose</groupId><artifactId>aspose-cells</artifactId><version>17.3.0</version></dependency><dependency><groupId>aspose</groupId><artifactId>aspose-slides</artifactId><version>17.2-jdk16</version></dependency><dependency><groupId>aspose</groupId><artifactId>aspose-words</artifactId><version>17.3.0-jdk16</version></dependency>
转静态HTML文件核心逻辑如下
package mon.utils;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.util.ArrayList;import java.util.Arrays;import java.util.HashMap;import java.util.List;import java.util.Map;import javax.servlet.http.HttpServletRequest;import mons.collections.CollectionUtils;import mons.lang3.StringUtils;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import com.aspose.cells.Workbook;import com.aspose.slides.Presentation;import com.aspose.words.Document;import com.aspose.words.SaveFormat;import com.hrsj.mcc.base.system.service.IFileOperateService;public class TransferToHtmlThread extends Thread{private static final Logger logger = LoggerFactory.getLogger(TransferToHtmlThread.class);private String sourceFileRoot;private String htmlPathRoot;private List<Map<String, Object>> fileList;private HttpServletRequest req;private String tranFileType;private String fontPath;public TransferToHtmlThread(String sourceFileRoot, String htmlPathRoot, List<Map<String, Object>> fileList, HttpServletRequest req, String tranFileType,String fontPath) {this.sourceFileRoot = sourceFileRoot;this.htmlPathRoot = htmlPathRoot + File.separator + "filedownload" + File.separator;this.fileList = fileList;this.req = req;this.tranFileType = tranFileType;this.fontPath = fontPath;}@Overridepublic void run() {String sourceFilePath = "";String htmlPathPath = "";String filePath = "";File file = null;List<Map<String,String>> files = null;InputStream is = null;String fileName = null;String fileType = null;try {files = new ArrayList<Map<String,String>>();for(Map<String, Object> fileInfo: fileList) {filePath = String.valueOf(fileInfo.get("file_path")); // 存储在DB的文件路径fileName = String.valueOf(fileInfo.get("saved_name")); // 文件名称fileType = fileName.substring(fileName.lastIndexOf(".") + 1).toLowerCase(); // 获取文件后缀List<String> tranTypeList = Arrays.asList(this.tranFileType.split(","));if (!tranTypeList.contains(fileType)) { // 不属于xlsx,xls,docx,doc,pptx,ppt,pdf类型文件不转HTMLcontinue;}sourceFilePath = sourceFileRoot + File.separator + filePath; // 原文件路径htmlPathPath = htmlPathRoot + filePath + ".html"; // 生成的HTML文件路径is = getClass().getResourceAsStream("/Aspose.Total.Java.lic"); // License认证文件，如果没有此认证，最多只能转3页//readContent(is);if (StringUtils.startsWith(fileType, "doc")) {com.aspose.words.License wordLicense = new com.aspose.words.License();wordLicense.setLicense(is);Document doc = new Document(sourceFilePath);doc.save(htmlPathPath, SaveFormat.HTML);}else if (StringUtils.startsWith(fileType, "xls")) {com.aspose.cells.License excelLicense = new com.aspose.cells.License();excelLicense.setLicense(is);Workbook book = new Workbook(sourceFilePath);book.save(htmlPathPath, com.aspose.cells.SaveFormat.HTML);}else if (StringUtils.startsWith(fileType, "ppt")) {com.aspose.slides.License pptLicense = new com.aspose.slides.License();pptLicense.setLicense(is);Presentation doc = new Presentation(sourceFilePath);doc.save(htmlPathPath, com.aspose.slides.SaveFormat.Html);}else if (StringUtils.startsWith(fileType, "pdf")) {com.aspose.pdf.License pdfLicense = new com.aspose.pdf.License();pdfLicense.setLicense(is);com.aspose.pdf.Document.addLocalFontPath(fontPath);com.aspose.pdf.Document pdfDoc = new com.aspose.pdf.Document(sourceFilePath);pdfDoc.save(htmlPathPath, com.aspose.pdf.SaveFormat.Html);}htmlPathPath = htmlPathPath.replace(htmlPathRoot, ""); // 去掉配置文件指定路径Map<String,String> map = new HashMap<String, String>();map.put("id", String.valueOf(fileInfo.get("id")));map.put("tranPath", htmlPathPath);files.add(map);}if (CollectionUtils.isNotEmpty(files)) {IFileOperateService fileOperateService = (IFileOperateService) SpringUtils.getBean("fileOperateService");fileOperateService.updateTransFilePath(files);//保存转换后的静态资源文件路径到DB}}catch (Exception e) {logger.error("Transfer File to Html fail,The message is:", e);}finally {try {if (is != null) {is.close();}} catch (IOException e) {}}}}
启异步线程将附件转成HTMl，核心逻辑如下
String tranFileType ="txt,xlsx,xls,docx,doc,pptx,ppt,zip,rar,img,jpg,pdf";String filePath =/usr/mairuan/upload/";//PC端上传附件的存放路径String tranFilePath ="/usr/mairuan/filepath/tran";//转换后静态资源文件的存放路径List<Map<String,Object>> fileList = fileOperateService.uploadFile(multiFile, filePath);String fontPath = req.getSession().getServletContext().getRealPath("/fonts/");//PDF转出来在服务端预览时可能会出现乱码，需要一些字体支持new Thread(new TransferToHtmlThread(filePath,tranFilePath,fileList,req,tranFileType,fontPath)).start();
部署一个空的Tomcat，在Tomcat的server.xml中配置静态资源文件存放根路径，手机端预览附件时，直接请求这个Tomcat提供的服务即可
<Context docBase="/usr/mairuan/filepath/tran" path="/mairuan.mobile" reloadable="false"/>
