itext7设置标签样式ITagWorkerFactory报凑No worker found for tag em

出现"No worker found for tag"的错误通常是因为缺少相应的标签工厂类。在iText7中，标签工厂类可以通过实现ITagWorkerFactory接口来创建。

针对你提到的"em"标签，可以尝试以下代码：

class EmTagWorkerFactory implements ITagWorkerFactory {
    @Override
    public ITagWorker createTagWorker(IElementNode tag, ProcessorContext context) {
        return new EmTagWorker(tag, context);
    }
}

class EmTagWorker implements ITagWorker {
    private ProcessorContext context;
    private IElementNode tag;

    public EmTagWorker(IElementNode tag, ProcessorContext context) {
        this.tag = tag;
        this.context = context;
    }

    @Override
    public void processEnd(IElementNode endElement, ProcessorContext context) {
        // do nothing
    }

    @Override
    public void process(ProcessorContext context) {
        // do nothing
    }
}

然后在创建PDF的过程中，将该工厂类添加到HtmlConverter类的构造函数中即可：

HtmlConverter.convertToPdf(html, os, new ConverterProperties()
        .setBaseUri(baseUri)
        .setTagWorkerFactory(new DefaultTagWorkerFactory() {
            @Override
            public ITagWorker getCustomTagWorker(IElementNode tag) {
                if ("em".equalsIgnoreCase(tag.name())) {
                    return new EmTagWorkerFactory().createTagWorker(tag, this);
                }
                return super.getCustomTagWorker(tag);
            }
        }));

这样，在HTML中使用"em"标签时，就可以正常转换为PDF了。