Apache pdfbox java.io.IOException: The TrueType font null does not contain a 'cmap' table

尝试使用Apache pdfbox 添加中文到pdf中，发现出现The TrueType font null does not contain a 'cmap' table，主要原因是遍历pdf页数时调用PDDocument#save 导致清空fontsToSubset，所以报错。

/**
*错误代码
*/
public void addPDFEachPageFont(File file) throws IOException{ 
PDDocument docs = PDDocument.load(file); 
Resource resource = new ClassPathResource("fonts/FZYTK.TTF"); 
PDFont font = PDType0Font.load(docs, resource.getInputStream()); 
for (int i = 0; i < docs.getNumberOfPages(); i++) { 
PDPage page = docs.getPage(i); 
PDPageContentStream contentStream = new PDPageContentStream(docs, page, PDPageContentStream.AppendMode.APPEND, false, true); 
contentStream.beginText(); contentStream.setFont(font, 12);
contentStream.newLineAtOffset(156, 129);
contentStream.showText(context); 
contentStream.endText();
 contentStream.close(); 
docs.save(file); // 在循环中遍历,导致清空fontsToSubset出现报错
} 
docs.close 
}
/**
* 正确写法　　
*/
public void addPDFEachPageFont(File file) throws IOException{ 
PDDocument docs = PDDocument.load(file); 
Resource resource = new ClassPathResource("fonts/FZYTK.TTF"); 
PDFont font = PDType0Font.load(docs, resource.getInputStream()); 
for (int i = 0; i < docs.getNumberOfPages(); i++) { 
PDPage page = docs.getPage(i); 
PDPageContentStream contentStream = new PDPageContentStream(docs, page, PDPageContentStream.AppendMode.APPEND, false, true);
contentStream.beginText(); contentStream.setFont(font, 12); 
contentStream.newLineAtOffset(156, 129); 
contentStream.showText(context);
contentStream.endText(); 
contentStream.close(); 
} 
docs.save(file); 
docs.close
}

源码解析

遍历所有的字体，进行font.subset() 之后，会清空fontsToSubset。然后再保存到原先的pdf文件中。

其中的字体文件是windwos10 中C:\Windows\Fonts\方正舒体获取