java - Servlet 使用 Apache FOP 抛出 Stackoverflow 错误

Question

我正在尝试创建一个 XML 文件，并根据该文件和一个 XSL 文件创建一个新的 PDF。问题是昨天一切正常。 今天我重新运行该程序，每次我想创建 PDF 时它都会突然崩溃。
我正在使用 Apache FOP 9.5 创建 PDF，在错误发生之前我在日志中看到的最后几行是

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javax.servlet.ServletException: Servlet execution threw an exception at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:314) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.t_systems.pif_frontend.tools.UTF8Filter.doFilter(UTF8Filter.java:164) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:537) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1085) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658) at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1556) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1513) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.StackOverflowError

在那行之后，我收到了很多这样的行:

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at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:709) at java.lang.StringBuffer.append(StringBuffer.java:421) at org.apache.fop.fo.properties.PercentLength.toString(PercentLength.java:121) at java.lang.String.valueOf(String.java:2981) at java.lang.StringBuffer.append(StringBuffer.java:265) at org.apache.fop.fo.flow.table.TableColumn.toString(TableColumn.java:233) at java.lang.String.valueOf(String.java:2981) at java.lang.StringBuffer.append(StringBuffer.java:265) at org.apache.fop.datatypes.LengthBase.toString(LengthBase.java:135) at java.lang.String.valueOf(String.java:2981) at java.lang.StringBuffer.append(StringBuffer.java:265) at org.apache.fop.fo.properties.PercentLength.toString(PercentLength.java:121) at java.lang.String.valueOf(String.java:2981) at java.lang.StringBuffer.append(StringBuffer.java:265) at org.apache.fop.fo.flow.table.TableColumn.toString(TableColumn.java:233)

这些行重复多次。 从我的日志记录中，我看到程序到达了以下代码部分:

Fop fop;
        fop = FopFactory.newInstance().newFop(MimeConstants.MIME_PDF, pdf);
        logger.debug("FactoryManager created");
        Source xml = new StreamSource(xmlFile);
        Source xsl = new StreamSource(xslFile);
        logger.debug("StreamSources created");
        Result sax = new SAXResult(fop.getDefaultHandler());
        logger.debug("Result created");
        Transformer transformer = TransformerFactory.newInstance().newTransformer(xsl);
        logger.debug("Tranformator created"); //This is the last line that gets printed before the crashing occures
        transformer.transform(xml, sax);
        logger.debug("Transformation done"); //This line is not printed out

我认为

transformer.transform(xml, sax);

线路导致了错误，但几天前它工作正常，没有任何变化。
有人知道这里可能是什么问题吗？我见过一些人写过关于永无止境的递归调用的文章，但这里的情况并非如此，因为我只调用该函数一次，并根据结果转发到另一个页面。

Answer 1

好吧，answear 似乎缺少 log4j.properties 文件。

在项目中，此文件丢失，这就是导致崩溃的原因。添加属性文件后，一切正常。