在解析xml时 要注意一个问题那就是 “<?xml version="1.0" encoding="UTF-8"?> ” 之前不能有空格，如果出现空格就会报如下异常，所以在写xml文件时要注意不能在开始有空格！

org.dom4j.DocumentException: Error on line 1 of document  : The processing instruction target matching "[xX][mM][lL]" is not allowed. Nested exception: The processing instruction target matching "[xX][mM][lL]" is not allowed.
	at org.dom4j.io.SAXReader.read(SAXReader.java:482)
	at org.dom4j.io.SAXReader.read(SAXReader.java:365)
	at com.soufun.last.ad.utils.MySAXReader.FileReader(MySAXReader.java:71)
	at com.soufun.last.ad.utils.MySAXReader.main(MySAXReader.java:81)
Nested exception: 
org.xml.sax.SAXParseException: The processing instruction target matching "[xX][mM][lL]" is not allowed.
	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:195)
	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:174)
	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:388)
	at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1427)
	at com.sun.org.apache.xerces.internal.impl.XMLScanner.scanPIData(XMLScanner.java:714)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanPIData(XMLDocumentFragmentScannerImpl.java:1020)
	at com.sun.org.apache.xerces.internal.impl.XMLScanner.scanPI(XMLScanner.java:682)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:953)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:647)
	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
	at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
	at org.dom4j.io.SAXReader.read(SAXReader.java:465)
	at org.dom4j.io.SAXReader.read(SAXReader.java:365)