dom4j解析xml-取消doctype中DTD验证设置
在编写⽤dom4j解析iBatis的sqlmap⽂件时，抛出以下异常信息：
org.dom4j.DocumentException: Nested exception:
at org.dom4j.ad(SAXReader.java:484)
at org.dom4j.ad(SAXReader.java:264)
...
Nested exception:
java.UnknownHostException:
at t(Unknown Source)
at t(Unknown Source)
at t(Unknown Source)
at sun.NetworkClient.doConnect(Unknown Source)
at sun.www.http.HttpClient.openServer(Unknown Source)
at sun.www.http.HttpClient.openServer(Unknown Source)
at sun.www.http.HttpClient.<init>(Unknown Source)
at sun.www.http.HttpClient.New(Unknown Source)
at sun.www.http.HttpClient.New(Unknown Source)
at sun.www.protocol.NewHttpClient(Unknown Source)
at sun.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.www.protocol.t(Unknown Source)
at sun.www.protocol.InputStream(Unknown Source)
at s.internal.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
at s.internal.impl.XMLEntityManager.startEntity(Unknown Source)
at s.internal.impl.XMLEntityManager.startDTDEntity(Unknown Source)
at s.internal.impl.XMLDTDScannerImpl.setInputSource(Unknown Source)
at s.internal.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(Unknown Source)
at s.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at s.internal.parsers.XML11Configuration.parse(Unknown Source)
at s.internal.parsers.XML11Configuration.parse(Unknown Source)
at s.internal.parsers.XMLParser.parse(Unknown Source)
at s.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at org.dom4j.ad(SAXReader.java:465)
at org.dom4j.ad(SAXReader.java:264)
...
Nested exception: java.UnknownHostException:
at t(Unknown Source)
at t(Unknown Source)
at t(Unknown Source)
at sun.NetworkClient.doConnect(Unknown Source)
at sun.www.http.HttpClient.openServer(Unknown Source)
at sun.www.http.HttpClient.openServer(Unknown Source)
at sun.www.http.HttpClient.<init>(Unknown Source)
at sun.www.http.HttpClient.New(Unknown Source)
使用dom4j解析xml文件
at sun.www.http.HttpClient.New(Unknown Source)
at sun.www.protocol.NewHttpClient(Unknown Source)
at sun.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.www.protocol.t(Unknown Source)
at sun.www.protocol.InputStream(Unknown Source)
at s.internal.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
at s.internal.impl.XMLEntityManager.startEntity(Unknown Source)
at s.internal.impl.XMLEntityManager.startDTDEntity(Unknown Source)
at s.internal.impl.XMLDTDScannerImpl.setInputSource(Unknown Source)
at s.internal.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(Un
known Source)
at s.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at s.internal.parsers.XML11Configuration.parse(Unknown Source)
at s.internal.parsers.XML11Configuration.parse(Unknown Source)
at s.internal.parsers.XMLParser.parse(Unknown Source)
at s.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at org.dom4j.ad(SAXReader.java:465)
at org.dom4j.ad(SAXReader.java:264)
粗体标注的是异常的关键信息，看到此问题相信很多朋友都知道是因为下载doctype中的dtd对xml进⾏验证时,⽹络不通所致,sqlmap中doctype 定义如下：
<!DOCTYPE sqlMap PUBLIC "-////DTD SQL Map 2.0//EN" "/dtd/sql-map-2.dtd">
但实际情况是很多时候程序运⾏的环境⽹络不⼀定和互联⽹是通的,⽽且像这样每次联⽹去下载dtd也会对程序的效率产⽣影响.于是，出现两种解决办法:
1、去掉xml⽂件中的doctype或者将doctype中指定的互联⽹dtd⽂件改为引⽤本地dtd⽂件
2、对dom4j的SAXReader进⾏设置，不去下载外部dtd⽂件来对xml进⾏验证
相信⼤部分同仁都不⼤会同意第⼀种办法，呵呵，我也不太赞同。于是开始寻第⼆种⽅案的解决办法：
reader.setValidation(false);
reader.setFeature("/xml/features/nonvalidating/load-external-dtd", false); 两⾏代码解决问题，关键是第⼆⾏。

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