问题描述
我们正在使用Java 8和Java的XML Stream API在单个线程应用程序中合并两个xml。
下面是我尝试合并到最终xml的两个示例输入xml。在下面的两个示例xml中,html_tabs很常见 元素,因此在最终XML中必须只有一个html_tabs元素。
Sample XML 1
-----------------------
<?xml version='1.0' encoding='UTF-8'?>
<html_tabs lastRefreshDataDate="">
<tab code="H_test_1" companyCode="H_test_1"
id="H_test_1">
<table>
<tr><td>testing1 template</td></tr>
</table>
</tab>
</html_tabs>
Sample XML2
-----------------------
<?xml version='1.0' encoding='UTF-8'?>
<html_tabs lastRefreshDataDate="">
<tab code="H_test_2" companyCode="H_test_2"
id="H_test_2">
<table>
<tr><td>testing2 template</td></tr>
</table>
</tab>
</html_tabs>
Merged XML
---------------
<?xml version='1.0' encoding='UTF-8'?>
<html_tabs lastRefreshDataDate="">
<tab code="H_test_1" companyCode="H_test_1"
id="H_test_1">
<table>
<tr><td>testing1 template</td></tr>
</table>
</tab>
<tab code="H_test_2" companyCode="H_test_2"
id="H_test_2">
<table>
<tr><td>testing2 template</td></tr>
</table>
</tab>
</html_tabs>
下面是我尝试通过跳过html_tabs元素来合并两个xml的代码。为了使问题简短,我已跳过导入语句。
public class MergeXML1 {
/**
* @param args
*/
public static void main(String[] args) throws Exception {
XMLEventWriter eventWriter;
XMLEventFactory eventFactory;
XMLOutputFactory outputFactory = XMLOutputFactory.newInstance();
XMLInputFactory inputFactory = XMLInputFactory.newInstance();
eventWriter = outputFactory.createXMLEventWriter(new FileOutputStream("testMerge1.xml"));
eventFactory = XMLEventFactory.newInstance();
// Create and write Start Tag
XMLEvent statAbEvent = eventFactory.createStartDocument();
eventWriter.add(statAbEvent);
statAbEvent = eventFactory.createStartElement(StringUtils.EMPTY,StringUtils.EMPTY,"html_tabs");
eventWriter.add(statAbEvent);
statAbEvent = eventFactory.createAttribute("lastRefreshDataDate",StringUtils.EMPTY);
eventWriter.add(statAbEvent);
String[] filenames = new String[]{"4102530_1_statabfinsum.xml","4102530_2_statabfinsum.xml"};
for (String filename : filenames) {
XMLEventReader test = inputFactory.createXMLEventReader(filename,new FileInputStream(filename));
System.out.println("read the first file : " + filename);
while (test.hasNext()) {
XMLEvent event = test.nextEvent();
if (event.getEventType() != XMLEvent.START_DOCUMENT && event.getEventType() != XMLEvent.END_DOCUMENT) {
if (event.isstartElement()) {
StartElement startElement = event.asstartElement();
System.out.println("element name:" + startElement.getName().getLocalPart());
if (!startElement.getName().getLocalPart().equals("html_tabs")) {
eventWriter.add(event);
continue;
} else {
continue;
}
}
eventWriter.add(event);
}
}
test.close();
}
eventWriter.add(eventFactory.createEndElement("","","html_tabs"));
eventWriter.add(eventFactory.createEndDocument());
eventWriter.close();
}
}
Exception in thread "main" javax.xml.stream.XMLStreamException: Trying to output second root,<tab>
at com.ctc.wstx.sw.BaseStreamWriter.throwOutputError(BaseStreamWriter.java:1589)
at com.ctc.wstx.sw.BaseStreamWriter.throwOutputError(BaseStreamWriter.java:1596)
at com.ctc.wstx.sw.BaseStreamWriter.reportNwfStructure(BaseStreamWriter.java:1624)
at com.ctc.wstx.sw.BaseNsstreamWriter.checkStartElement(BaseNsstreamWriter.java:483)
at com.ctc.wstx.sw.SimpleNsstreamWriter.writeStartOrEmpty(SimpleNsstreamWriter.java:257)
at com.ctc.wstx.sw.BaseNsstreamWriter.writeStartElement(BaseNsstreamWriter.java:325)
at org.codehaus.stax2.ri.Stax2EventWriterImpl.add(Stax2EventWriterImpl.java:100)
at com.citi.research.distribution.tasks.downloadtasks.MergeXML1.main(MergeXML1.java:60)
由于出现异常,我无法找出上述代码出了什么问题。
谢谢您的帮助
解决方法
在检查代码的基础上,似乎您将最后一个EndElement
从第一个文件复制到了输出,从而使您回到顶层。然后,当您尝试从第二个文件中写入(正确的)StartElement
时,您试图将其插入根目录。
从第一个文件中过滤(即不写)EndElement
。