一、寫在所有之前：
因為dom4j和jdom在這個問題上處理的方法是一模一樣的，只是一個是SAXBuilder 一個SAXReader，這裡以jdom距離，至於dom4j只需要同理替換一下就可以了。
二、問題發生的情況
當你用jdom讀取一個有dtd驗證的xml檔案,同時你的網路是不通的情況下。會出現以下錯誤：
1，程式碼如下

dom;

java.io.File;

org.jdom.Document;

org.jdom.input.SAXBuilder;

{
publicstaticvoidmain(String[]args)

{
Filefile=newFile("./src/dom/aiwf_aiService.xml");
if(file.exists()){
SAXBuilderbuilder=newSAXBuilder();
try{
Documentdoc=builder.build(file);
System.out.println(doc);
}catch(Exceptione){
e.printStackTrace();
}
}else{
System.out.println("cannotfindxmlfile:"
+file.getAbsolutePath());
}
}
}

2,xml檔案

...............

3，錯誤如下

java.net.SocketException:Permissiondenied:connect
atjava.net.PlainSocketImpl.socketConnect(NativeMethod)
atjava.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:

)
atjava.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:

)
atjava.net.PlainSocketImpl.connect(PlainSocketImpl.java:

)
atjava.net.Socket.connect(Socket.java:

)
atjava.net.Socket.connect(Socket.java:

)
atsun.net.NetworkClient.doConnect(NetworkClient.java:

)
atsun.net.www.http.HttpClient.openServer(HttpClient.java:

)
atsun.net.www.http.HttpClient.openServer(HttpClient.java:

)
atsun.net.www.http.HttpClient.

)
atsun.net.www.http.HttpClient.New(HttpClient.java:

)
atsun.net.www.http.HttpClient.New(HttpClient.java:

)
atsun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:

)
atsun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:

)
atsun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:

)
atsun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:

)
atcom.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:

)
atcom.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:

)
atcom.sun.org.apache.xerces.internal.impl.XMLEntityManager.startDTDEntity(XMLEntityManager.java:

)
atcom.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.setInputSource(XMLDTDScannerImpl.java:

)
atcom.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(XMLDocumentScannerImpl.java:

)
atcom.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:

)
atcom.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:

)
atcom.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:

)
atcom.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:

)
atcom.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:

)
atorg.jdom.input.SAXBuilder.build(SAXBuilder.java:

)
atorg.jdom.input.SAXBuilder.build(SAXBuilder.java:

)
atorg.jdom.input.SAXBuilder.build(SAXBuilder.java:

)
atdom.TestJdom.main(TestJdom.java:

)

HowdoIkeeptheDTDfromloading?EvenwhenIturnoffvalidationtheparsertriestoloadtheDTDfile.

Evenwhenvalidationisturnedoff,anXMLparserwillbydefaultloadtheexternalDTDfileinordertoparsetheDTDforexternalentitydeclarations.Xerceshasafeaturetoturnoffthisbehaviornamed"http://apache.org/xml/features/nonvalidating/load-external-dtd"andifyouknowyou'reusingXercesyoucansetthisfeatureonthebuilder.

builder.setFeature(
"http://apache.org/xml/features/nonvalidating/load-external-dtd",false);

Ifyou'reusinganotherparserlikeCrimson,yourbestbetistosetupanEntityResolverthatresolvestheDTDwithoutactuallyreadingtheseparatefile.

importorg.xml.sax.*;
importjava.io.*;

publicclassNoOpEntityResolverimplementsEntityResolver{
publicInputSourceresolveEntity(StringpublicId,StringsystemId){
returnnewInputSource(newStringBufferInputStream(""));
}
}

Theninthebuilder


builder.setEntityResolver(newNoOpEntityResolver());

Thereisadownsidetothisapproach.Anyentitiesinthedocumentwillberesolvedtotheemptystring,andwilleffectivelydisappear.Ifyourdocumenthasentities,youneedtosetExpandEntities(false)codeandensuretheEntityResolveronlysuppressestheDocType.

{
publicInputSourceresolveEntity(StringpublicId,StringsystemId){
returnnewInputSource(newStringBufferInputStream(""));
}
}

通過builder.setEntityResolver(newNoOpEntityResolver())方法來隱蔽起dtd驗證器。這樣就不會出錯了。試了一下確實沒問題了。但要知道xml沒有dtd驗證是不好的，我們是否能讓它使用本地dtd驗證呢。例如本文的oswork
我把驗證檔案workflow_2_8.dtd拷貝到本地，能否驗證的時候用本地的呢？
3，用本地dtd驗證
方法有兩種
方法一、更改xml中的doctype宣告，但是一般情況下更改這個是不好的。更改後就不是標準的了。
方法二、驗證期替換
看到上邊FAQ講的方法你是否有什麼靈感呢？
看看下邊這段程式碼

dom;

java.io.File;

java.io.IOException;

org.jdom.Document;

org.jdom.input.SAXBuilder;

org.xml.sax.EntityResolver;

org.xml.sax.InputSource;

org.xml.sax.SAXException;

{
publicstaticvoidmain(String[]args){
Filefile=newFile("./src/dom/aiwf_aiService.xml");
if(file.exists()){
SAXBuilderbuilder=newSAXBuilder();
builder.setValidation(false);
builder.setEntityResolver(newEntityResolver(){
publicInputSourceresolveEntity(StringpublicId,
StringsystemId)throwsSAXException,IOException{
returnnewInputSource("./workflow_2_8.dtd");
}
});
try{
Documentdoc=builder.build(file);
System.out.println(doc);
}catch(Exceptione){
e.printStackTrace();
}
}else{
System.out.println("cannotfindxmlfile:"
+file.getAbsolutePath());
}
}
}

對了，同樣是自己實現一個EntityResolver(這裡用了匿名類)，不同的是在裡邊使用本地的dtd驗證
另外，匿名類內部，似乎這樣寫起來更順眼些

);
InputSourceis

InputSource(stream);
is.setPublicId(publicId);
is.setSystemId(systemId);