Java实现Word、Excel、PDF文件在线预览

在线预览文档通常有几种方案：转换为HTML、转换为PDF再预览、使用专门的预览服务等。下面我将介绍几种实现方式。

方案一：使用开源库转换为HTML预览

1. 添加Maven依赖

XML 复制代码

<dependencies>
    <!-- Word处理 -->
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>5.2.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>5.2.3</version>
    </dependency>
    
    <!-- Excel处理 -->
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-scratchpad</artifactId>
        <version>5.2.3</version>
    </dependency>
    
    <!-- PDF处理 -->
    <dependency>
        <groupId>org.apache.pdfbox</groupId>
        <artifactId>pdfbox</artifactId>
        <version>2.0.27</version>
    </dependency>
    
    <!-- 文件类型检测 -->
    <dependency>
        <groupId>org.apache.tika</groupId>
        <artifactId>tika-core</artifactId>
        <version>2.4.1</version>
    </dependency>
    
    <!-- Spring Boot Web -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <version>2.7.0</version>
    </dependency>
    
    <!-- 模板引擎 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
        <version>2.7.0</version>
    </dependency>
</dependencies>

2. 文件预览服务实现

java 复制代码

import org.apache.poi.hwpf.HWPFDocument;
import org.apache.poi.hwpf.converter.WordToHtmlConverter;
import org.apache.poi.xwpf.usermodel.XWPFDocument;
import org.apache.poi.xwpf.converter.xhtml.XHTMLConverter;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.text.PDFTextStripper;
import org.springframework.stereotype.Service;
import org.w3c.dom.Document;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import java.io.*;

@Service
public class FilePreviewService {

    /**
     * 预览Word文档（转换为HTML）
     */
    public String previewWord(File file) throws Exception {
        String fileName = file.getName().toLowerCase();
        
        if (fileName.endsWith(".doc")) {
            return convertDocToHtml(file);
        } else if (fileName.endsWith(".docx")) {
            return convertDocxToHtml(file);
        } else {
            throw new IllegalArgumentException("不支持的Word格式");
        }
    }

    /**
     * 预览Excel文档（转换为HTML表格）
     */
    public String previewExcel(File file) throws Exception {
        String fileName = file.getName().toLowerCase();
        Workbook workbook;
        
        try (FileInputStream fis = new FileInputStream(file)) {
            if (fileName.endsWith(".xls")) {
                workbook = new HSSFWorkbook(fis);
            } else if (fileName.endsWith(".xlsx")) {
                workbook = new XSSFWorkbook(fis);
            } else {
                throw new IllegalArgumentException("不支持的Excel格式");
            }
            
            return convertExcelToHtml(workbook);
        }
    }

    /**
     * 预览PDF文档（提取文本内容）
     */
    public String previewPdf(File file) throws Exception {
        try (PDDocument document = PDDocument.load(file)) {
            PDFTextStripper stripper = new PDFTextStripper();
            String text = stripper.getText(document);
            
            // 简单的HTML包装
            return "<html><body><pre>" + escapeHtml(text) + "</pre></body></html>";
        }
    }

    /**
     * 通用文件预览方法
     */
    public String previewFile(File file) throws Exception {
        String fileName = file.getName().toLowerCase();
        
        if (fileName.endsWith(".doc") || fileName.endsWith(".docx")) {
            return previewWord(file);
        } else if (fileName.endsWith(".xls") || fileName.endsWith(".xlsx")) {
            return previewExcel(file);
        } else if (fileName.endsWith(".pdf")) {
            return previewPdf(file);
        } else {
            throw new IllegalArgumentException("不支持的文件格式");
        }
    }

    // 私有方法：具体转换实现
    private String convertDocToHtml(File file) throws Exception {
        try (HWPFDocument document = new HWPFDocument(new FileInputStream(file))) {
            WordToHtmlConverter converter = new WordToHtmlConverter(
                DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument()
            );
            converter.processDocument(document);
            
            Document htmlDocument = converter.getDocument();
            return convertDocumentToString(htmlDocument);
        }
    }

    private String convertDocxToHtml(File file) throws Exception {
        try (XWPFDocument document = new XWPFDocument(new FileInputStream(file))) {
            StringWriter writer = new StringWriter();
            XHTMLConverter.getInstance().convert(document, writer, null);
            return writer.toString();
        }
    }

    private String convertExcelToHtml(Workbook workbook) {
        StringBuilder html = new StringBuilder();
        html.append("<html><body><table border='1'>");
        
        for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
            Sheet sheet = workbook.getSheetAt(i);
            html.append("<tr><th colspan='10'>").append(sheet.getSheetName()).append("</th></tr>");
            
            for (Row row : sheet) {
                html.append("<tr>");
                for (Cell cell : row) {
                    html.append("<td>");
                    switch (cell.getCellType()) {
                        case STRING:
                            html.append(escapeHtml(cell.getStringCellValue()));
                            break;
                        case NUMERIC:
                            html.append(cell.getNumericCellValue());
                            break;
                        case BOOLEAN:
                            html.append(cell.getBooleanCellValue());
                            break;
                        default:
                            html.append(" ");
                    }
                    html.append("</td>");
                }
                html.append("</tr>");
            }
        }
        
        html.append("</table></body></html>");
        return html.toString();
    }

    private String convertDocumentToString(org.w3c.dom.Document doc) throws Exception {
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer transformer = tf.newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
        transformer.setOutputProperty(OutputKeys.METHOD, "html");
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
        
        StringWriter writer = new StringWriter();
        transformer.transform(new DOMSource(doc), new StreamResult(writer));
        return writer.toString();
    }

    private String escapeHtml(String text) {
        return text.replace("&", "&amp;")
                  .replace("<", "&lt;")
                  .replace(">", "&gt;")
                  .replace("\"", "&quot;")
                  .replace("'", "&#39;");
    }
}

3. Spring Boot控制器

java 复制代码

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;

import java.io.File;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

@Controller
public class FilePreviewController {

    @Autowired
    private FilePreviewService filePreviewService;

    private final Path rootLocation = Paths.get("upload-dir");

    @GetMapping("/")
    public String index() {
        return "upload";
    }

    @PostMapping("/upload")
    public String handleFileUpload(@RequestParam("file") MultipartFile file, Model model) {
        try {
            // 创建上传目录
            if (!Files.exists(rootLocation)) {
                Files.createDirectories(rootLocation);
            }

            // 保存文件
            Path destinationFile = rootLocation.resolve(
                Paths.get(file.getOriginalFilename()))
                .normalize().toAbsolutePath();
            file.transferTo(destinationFile.toFile());

            // 预览文件
            String htmlContent = filePreviewService.previewFile(destinationFile.toFile());
            model.addAttribute("previewContent", htmlContent);
            model.addAttribute("fileName", file.getOriginalFilename());

            return "preview";

        } catch (Exception e) {
            model.addAttribute("error", "文件预览失败: " + e.getMessage());
            return "upload";
        }
    }

    @GetMapping("/preview/{filename:.+}")
    @ResponseBody
    public ResponseEntity<String> previewFile(@PathVariable String filename) {
        try {
            Path file = rootLocation.resolve(filename);
            String htmlContent = filePreviewService.previewFile(file.toFile());
            return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_TYPE, "text/html; charset=utf-8")
                .body(htmlContent);
        } catch (Exception e) {
            return ResponseEntity.badRequest().body("预览失败: " + e.getMessage());
        }
    }

    @GetMapping("/download/{filename:.+}")
    @ResponseBody
    public ResponseEntity<Resource> downloadFile(@PathVariable String filename) {
        try {
            Path file = rootLocation.resolve(filename);
            Resource resource = new UrlResource(file.toUri());
            
            return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_DISPOSITION, 
                    "attachment; filename=\"" + resource.getFilename() + "\"")
                .body(resource);
        } catch (Exception e) {
            return ResponseEntity.notFound().build();
        }
    }
}

4. HTML模板

src/main/resources/templates/upload.html

html 复制代码

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>文件上传预览</title>
</head>
<body>
    <h2>文件上传预览</h2>
    
    <form method="POST" enctype="multipart/form-data">
        <input type="file" name="file" accept=".doc,.docx,.xls,.xlsx,.pdf">
        <button type="submit">上传并预览</button>
    </form>
    
    <div th:if="${error}" style="color: red;">
        <p th:text="${error}"></p>
    </div>
</body>
</html>

src/main/resources/templates/preview.html

html 复制代码

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>文件预览</title>
    <style>
        .preview-container {
            border: 1px solid #ccc;
            padding: 20px;
            margin: 20px 0;
            max-height: 600px;
            overflow: auto;
        }
        .actions {
            margin: 10px 0;
        }
    </style>
</head>
<body>
    <h2>文件预览: <span th:text="${fileName}"></span></h2>
    
    <div class="actions">
        <a th:href="@{'/download/' + ${fileName}}">下载原文件</a> |
        <a href="/">返回上传</a>
    </div>
    
    <div class="preview-container" th:utext="${previewContent}">
        <!-- 预览内容将在这里显示 -->
    </div>
</body>
</html>

方案二：使用第三方服务（推荐用于生产环境）

对于生产环境，建议使用专门的文档预览服务：

使用Microsoft Office Online Server
使用Google Docs预览服务
使用专业的文档预览SDK（如GroupDocs、Aspose等）

使用Google Docs预览的示例：

java 复制代码

public String previewWithGoogleDocs(String fileUrl) {
    // 将文件上传到可访问的URL，然后使用Google Docs预览
    return "https://docs.google.com/gview?url=" + URLEncoder.encode(fileUrl, "UTF-8") + "&embedded=true";
}

方案三：使用专业的Java库（Aspose）

java 复制代码

// 需要购买许可证
import com.aspose.words.Document;
import com.aspose.words.HtmlSaveOptions;

public String previewWithAspose(File file) throws Exception {
    Document doc = new Document(file.getAbsolutePath());
    HtmlSaveOptions options = new HtmlSaveOptions();
    options.setExportImagesAsBase64(true);
    
    StringWriter writer = new StringWriter();
    doc.save(writer, options);
    return writer.toString();
}

启动类

java 复制代码

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class FilePreviewApplication {
    public static void main(String[] args) {
        SpringApplication.run(FilePreviewApplication.class, args);
    }
}

配置说明

在application.properties中添加：

html 复制代码

# 文件上传大小限制
spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB

#  thymeleaf配置
spring.thymeleaf.cache=false
spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.suffix=.html

使用说明

启动应用后访问 http://localhost:8080
上传Word、Excel或PDF文件
系统会自动转换为HTML格式进行预览

注意事项

性能考虑：大文件转换可能耗时，建议添加进度提示
内存管理：处理大文件时注意内存使用，建议使用流式处理
格式兼容性：复杂格式可能无法完美转换
安全性：对上传文件进行病毒扫描和类型验证
缓存策略：对已转换的文件进行缓存以提高性能

这种方案适合中小型项目的文档预览需求，对于企业级应用，建议使用专业的文档预览服务。

Java实现Word、Excel、PDF文件 在线预览

方案一：使用开源库转换为HTML预览

1. 添加Maven依赖

2. 文件预览服务实现

3. Spring Boot控制器

4. HTML模板

方案二：使用第三方服务（推荐用于生产环境）

使用Google Docs预览的示例：

方案三：使用专业的Java库（Aspose）

启动类

配置说明

使用说明

注意事项

Java实现Word、Excel、PDF文件在线预览