请帮我用java18使用springboot 设计一套docpdf上传后每一页按页数重命名后保存为图片到本地的方法

以下是一个基本的实现：

1. 在Spring Boot项目中添加依赖项org.apache.pdfbox和org.apache.poi，以便处理pdf和doc文件。
2. 创建一个名为FileUploadController的控制器类，其中包含一个处理上传文件的POST方法。此方法将使用MultipartFile对象接收上传的文件，并将其保存在本地文件系统上。然后，它将检查文件类型并使用适当的库将文件转换为图片。最后，它将重命名并保存所有生成的图像。

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.apache.poi.hwpf.extractor.WordExtractor;
import org.apache.poi.xwpf.extractor.XWPFWordExtractor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

@Controller
public class FileUploadController {
  
  @Value("${file.upload-dir}")
  private String fileUploadDir;
  
  @PostMapping("/upload")
  public ResponseEntity<String> uploadFile(@RequestParam("file") MultipartFile file) {
    
    try {
      
      // 保存上传的文件
      String fileName = file.getOriginalFilename();
      String filePath = fileUploadDir + File.separator + fileName;
      File dest = new File(filePath);
      file.transferTo(dest);
      
      // 检查文件类型并使用相应的库将其转换为图片
      List<String> imagePaths = new ArrayList<>();
      if (fileName.endsWith(".pdf")) {
        PDDocument document = PDDocument.load(dest);
        PDFRenderer pdfRenderer = new PDFRenderer(document);
        int numPages = document.getNumberOfPages();
        for (int i = 0; i < numPages; i++) {
          BufferedImage image = pdfRenderer.renderImageWithDPI(i, 300);
          String imagePath = fileUploadDir + File.separator + "page" + (i + 1) + ".png";
          ImageIO.write(image, "png", new File(imagePath));
          imagePaths.add(imagePath);
        }
        document.close();
      } else if (fileName.endsWith(".doc")) {
        WordExtractor extractor = new WordExtractor(dest);
        String text = extractor.getText();
        String[] pages = text.split("\f");
        for (int i = 0; i < pages.length; i++) {
          BufferedImage image = TextToImageConverter.convertTextToImage(pages[i]);
          String imagePath = fileUploadDir + File.separator + "page" + (i + 1) + ".png";
          ImageIO.write(image, "png", new File(imagePath));
          imagePaths.add(imagePath);
        }
      } else if (fileName.endsWith(".docx")) {
        XWPFWordExtractor extractor = new XWPFWordExtractor(new FileInputStream(dest));
        String text = extractor.getText();
        String[] pages = text.split("\f");
        for (int i = 0; i < pages.length; i++) {
          BufferedImage image = TextToImageConverter.convertTextToImage(pages[i]);
          String imagePath = fileUploadDir + File.separator + "page" + (i + 1) + ".png";
          ImageIO.write(image, "png", new File(imagePath));
          imagePaths.add(imagePath);
        }
      } else {
        // 不支持的文件类型
        return new ResponseEntity<>("Unsupported file type", HttpStatus.BAD_REQUEST);
      }
      
      // 重命名并保存所有生成的图像
      for (int i = 0; i < imagePaths.size(); i++) {
        String oldPath = imagePaths.get(i);
        String newPath = fileUploadDir + File.separator + "page" + (i + 1) + ".png";
        File oldFile = new File(oldPath);
        File newFile = new File(newPath);
        oldFile.renameTo(newFile);
      }
      
      return new ResponseEntity<>("File uploaded successfully", HttpStatus.OK);
      
    } catch (IOException e) {
      e.printStackTrace();
      return new ResponseEntity<>("Error uploading file", HttpStatus.INTERNAL_SERVER_ERROR);
    }
    
  }
  
}

3. 创建一个名为TextToImageConverter的帮助类，它将给定的文本转换为包含该文本的BufferedImage对象。

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

public class TextToImageConverter {
  
  private static final int FONT_SIZE = 12;
  
  public static BufferedImage convertTextToImage(String text) {
    BufferedImage image = new BufferedImage(500, 500, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = image.createGraphics();
    g2d.setColor(Color.WHITE);
    g2d.fillRect(0, 0, image.getWidth(), image.getHeight());
    g2d.setColor(Color.BLACK);
    g2d.setFont(new Font("Courier New", Font.PLAIN, FONT_SIZE));
    String[] lines = text.split("\n");
    int y = FONT_SIZE;
    for (String line : lines) {
      g2d.drawString(line, 0, y);
      y += FONT_SIZE;
    }
    g2d.dispose();
    return image;
  }
  
}

4. 在application.properties文件中添加一个名为file.upload-dir的属性，指定上传文件的保存路径。

file.upload-dir=/path/to/upload/dir

5. 运行Spring Boot应用程序并使用POST请求上传pdf或doc文件。每一页都将转换为一个png图像，并在本地文件系统上保存。图像将按页数重命名，例如page1.png，page2.png等等。