处理自定义UserAgentCallback图像时，飞碟出现异常

Question

我已经为飞碟R8设置了一个测试环境，并正在测试从模板和数据构建PDF。我使用自定义的UserAgentCallback从文件系统本地读取外部js/css和图像。引入以下自定义UserAgentCallback时出现问题：

package support;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;

import org.xhtmlrenderer.swing.NaiveUserAgent;

public class FileUserAgent extends NaiveUserAgent {
    @Override
    public String resolveURI(String uri) {
        URL url = null;
        String path = null;
        try {
            url = new URL(uri);
            path = url.getPath();
        } catch (MalformedURLException e) {
            // only path present
            path = uri;
        }
        if (path.charAt(0) == '/') {
            path = path.substring(1, path.length());
        }
        return path;
    }

    @Override
    protected InputStream resolveAndOpenStream(String filepath) {
        InputStream is = null;
        try {
            File file = new File(filepath);
            is = new FileInputStream(file);
        } catch (Exception e) {
            System.out.print("an error occured when reading resource: " + e.getMessage());
        }
        return is;
    }
}

UserAgentCallback可以毫无问题地读取CSS，但当从src或背景图像属性读取图像时，我得到了以下异常：

java.lang.ClassCastException: org.xhtmlrenderer.swing.AWTFSImage$OldAWTFSImage cannot be cast to org.xhtmlrenderer.pdf.ITextFSImage
    at org.xhtmlrenderer.pdf.ITextOutputDevice.drawImage(ITextOutputDevice.java:761)
    at org.xhtmlrenderer.render.AbstractOutputDevice.paintTiles(AbstractOutputDevice.java:300)
    at org.xhtmlrenderer.render.AbstractOutputDevice.paintBackground0(AbstractOutputDevice.java:245)
    at org.xhtmlrenderer.render.AbstractOutputDevice.paintBackground(AbstractOutputDevice.java:191)
    at org.xhtmlrenderer.pdf.ITextOutputDevice.paintBackground(ITextOutputDevice.java:187)
    at org.xhtmlrenderer.render.Box.paintBackground(Box.java:436)
    at org.xhtmlrenderer.layout.Layer.paintBackgroundsAndBorders(Layer.java:243)
    at org.xhtmlrenderer.layout.Layer.paint(Layer.java:329)
    at org.xhtmlrenderer.pdf.ITextRenderer.paintPage(ITextRenderer.java:384)
    at org.xhtmlrenderer.pdf.ITextRenderer.writePDF(ITextRenderer.java:348)
    at org.xhtmlrenderer.pdf.ITextRenderer.createPDF(ITextRenderer.java:315)
    at org.xhtmlrenderer.pdf.ITextRenderer.createPDF(ITextRenderer.java:246)

Answer 1

根据我在飞碟论坛上读到的内容，你必须确保返回正确的ImageResource！

对我有帮助的是用ITextUserAgent而不是NaiveUserAgent扩展这个类。(ITextUserAgent扩展了NaiveUserAgent)。