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在我的生产管道中，我需要从 HTML 生成数百个 PDF。对于这种情况，我首先将 HTML 转换为 XHTML。比我将“清理”的 XHTML 和 uri 传递给渲染器。

由于 *.css 和 imageFiles 对于所有 XHTML 文件都是相等的，因此我不需要在处理文件时一直解析它们。我成功使用以下代码缓存图像。我怎样才能缓存 .css 文件呢？我想避免将所有文件放入我的类路径中。

ITextRenderer renderer = new ITextRenderer();

ResourceLoaderUserAgent callback = new ResourceLoaderUserAgent(renderer.getOutputDevice());
callback.setSharedContext(renderer.getSharedContext());

for (MyObject myObject : myObjectList) {

    OutputStream os = new FileOutputStream(tempFile);

    final DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
    documentBuilderFactory.setValidating(false);
    DocumentBuilder builder = documentBuilderFactory.newDocumentBuilder();
    org.w3c.dom.Document document = builder.parse(myObject.getLocalPath); // full path to .xhtml

    renderer.getSharedContext().setUserAgentCallback(callback);

    renderer.setDocument(document, myObject.getUri());
    renderer.layout();
    renderer.createPDF(os);

    os.flush();
    os.close();
}
    ...


private static class ResourceLoaderUserAgent extends ITextUserAgent
{
    public ResourceLoaderUserAgent(ITextOutputDevice outputDevice) {
        super(outputDevice);
    }

    protected InputStream resolveAndOpenStream(String uri) {
        InputStream is = super.resolveAndOpenStream(uri);
        System.out.println("IN resolveAndOpenStream() " + uri);

        return is;
    }
}
4

1 回答 1

4

万一有人在这里遇到同样的问题，我就是这样解决的。由于我无法在我的 CustomUserAgent 中缓存 *.css 文件，我不得不找到另一种方法。我的解决方案使用Squid作为 http-proxy 来缓存所有经常使用的资源。

在我的 CustomUserAgent 中，我只需要通过传递代理对象来访问这个代理。

public class ResourceLoaderUserAgent extends ITextUserAgent {

public ResourceLoaderUserAgent(ITextOutputDevice outputDevice) {
    super(outputDevice);
}

protected InputStream resolveAndOpenStream(String uri) {    

    HttpURLConnection connection = null;
    URL proxyUrl = null;
    try {
        Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("localhost", 3128));
        proxyUrl = new URL(uri);
        connection = (HttpURLConnection) proxyUrl.openConnection(proxy);
        connection.connect();

    } catch (Exception e) {
        throw new RuntimeException(e);
    }

    java.io.InputStream is = null;
    try {
        is = connection.getInputStream();
    } catch (java.net.MalformedURLException e) {
        XRLog.exception("bad URL given: " + uri, e);
    } catch (java.io.FileNotFoundException e) {
        XRLog.exception("item at URI " + uri + " not found");
    } catch (java.io.IOException e) {
        XRLog.exception("IO problem for " + uri, e);
    }

    return is;
}
}

缓存：

resolving css took 74 ms
resolving images took 225 ms

未缓存：

resolving css took 15466 ms
resolving images took 11236 ms

如您所见，缓存资源和未缓存资源之间的差异很大

于 2012-08-07T09:04:38.310 回答