解析 xml 文件时出现未知主机异常

Question

当我尝试解析 xml 时，我得到以下异常：-

java.net.UnknownHostException: hibernate.sourceforge.net
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at sun.net.NetworkClient.doConnect(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.<init>(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
    at org.apache.xerces.impl.XMLEntityManager.startEntity(Unknown Source)
    at org.apache.xerces.impl.XMLEntityManager.startDTDEntity(Unknown Source)
    at org.apache.xerces.impl.XMLDTDScannerImpl.setInputSource(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
    at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
    at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
    at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
    at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
    at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)
    at javax.xml.parsers.DocumentBuilder.parse(Unknown Source)

我用来解析 xml 的代码如下：-

File hbmFile = new File(hbmFileName);
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(hbmFile);

我正在尝试解析为hibernate编写的xml，实际上它是一个hibernate映射文件。

我要解析的 xml 如下：-

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="org.hibernate.entity.Student" table="table_student">
        <id name="rollNo" column="rool_no" type="int"/>
        <property name="name" column="st_name" type="string"/>
        <set name="marks" table="table_marks">
            <key column="roll_no"/>
            <composite-element class="org.hibernate.entity.StudentMarks">
                <property name="subject" column="st_sub"/>
                <property name="marks" column="st_marks"/>
            </composite-element>
        </set>
    </class>
</hibernate-mapping>

请帮忙。

Answer 1

解析器正在尝试从hibernate.sourceforge.net 下载DTD 以验证已解析的XML。

但是，机器上的 DNS 客户端由于某种原因无法解析该主机名（它在我的机器上解析为 82.98.86.175）。

为避免此问题，您必须告诉DocumentBuilderFactory 忽略 DTD：

File hbmFile = new File(hbmFileName);
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

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

DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(hbmFile);

见Make DocumentBuilder.parse ignore DTD references。

Answer 2

我使用了以下代码，这对我来说很好..

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();  
dbf.setValidating(false);
DocumentBuilder db = dbf.newDocumentBuilder();
db.setEntityResolver(new EntityResolver() {
  @Override
  public InputSource resolveEntity(String arg0, String arg1)
        throws SAXException, IOException {
    if(arg0.contains("Hibernate")) {
        return new InputSource(new StringReader(""));
    } else {
        // TODO Auto-generated method stub
        return null;
    }
  }
});
Document doc = db.parse(hbmFile);

Answer 3

我也在尝试从带有 dtd 标记的 xml 文件中读取

<!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN" "http://www.w3.org/TR/speech-grammar/grammar.dtd">

和代码

File fXmlFile = new File(grammarXML);                   
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);

我遇到了同样的错误。

java.net.UnknownHostException:

部署代码的服务器无权访问 w3.org。当我在浏览器中打开 w3.org 时，它正在打开连接超时页面。我授予了 w3.org 的访问权限，它解决了这个问题。