java - JAXB:使用不同的命名空间解码类似的 XML

Question

我从 3 个不同的客户端获取 3 个不同的 xml 输入:

来自客户端 1 的输入 1:(命名空间前缀: ns2 ，命名空间 URL: url1 )

<ns2:myroot xmlns:ns2="url1">
   <ns2:mydata>
      <ns2:myrate>
         GBP 800.55
      </ns2:myrate>
   </ns2:mydata>
</ns2:myroot>

来自客户端 2 的输入 2:(命名空间前缀: ns5 ，命名空间 URL: url2 )

<ns5:myroot xmlns:ns5="url2">
   <ns5:mydata>
      <ns5:myrate>
         THB 1000.70
      </ns5:myrate>
   </ns5:mydata>
</ns5:myroot>

来自客户端 3 的输入 3:(命名空间前缀: <empty> ，命名空间 URL: url3 )

<myroot xmlns="url3">
   <mydata>
      <myrate>
         USD 955.25
      </myrate>
   </mydata>
</myroot>

这三个元素都有相同的元素名称，但命名空间不同。所以我写下了1个类文件包，名为MyRoot.java和MyData.java :

@XmlRootElement(name="myroot")
@XmlAccessorType(XmlAccessType.FIELD)
public class MyRoot
{   @XmlElement(name="mydata")
    protected MyData mydata;
    public MyData getMyData()
    {   return mydata;
    }
}


@XmlAccessorType(XmlAccessType.FIELD)
public class MyData
{   @XmlElement(name="myrate")
    protected String myRate;
    public String getMyRate()
    {   return myRate;
    }
}

这是我的测试方法:

public class Test {
    public static void main(String[]ar){
        for(String inputFileName:new String[]{"input3.xml","input2.xml","input1.xml"}){
            try{
                MyRoot myRoot = (MyRoot) JAXBContext.newInstance(MyRoot.class).createUnmarshaller().unmarshal(Test.class.getClassLoader().getResourceAsStream("data/xml/jaxb/varns/"+inputFileName));
                System.out.println(myRoot.getMyData());
            }catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

我的问题是:

1. 如果我添加namespace="url3"至@XmlRootElement/@XmlElement ，然后我得到:javax.xml.bind.UnmarshalException: unexpected element (uri:"url1", local:"myroot"). Expected elements are <{url3}myroot>和javax.xml.bind.UnmarshalException: unexpected element (uri:"url2", local:"myroot"). Expected elements are <{url3}myroot>
2. 如果我添加namespace="url2"至@XmlRootElement/@XmlElement ，然后我得到:javax.xml.bind.UnmarshalException: unexpected element (uri:"url1", local:"myroot"). Expected elements are <{url2}myroot>和javax.xml.bind.UnmarshalException: unexpected element (uri:"url3", local:"myroot"). Expected elements are <{url2}myroot>
3. 如果我添加namespace="url1"至@XmlRootElement/@XmlElement ，然后我得到:javax.xml.bind.UnmarshalException: unexpected element (uri:"url2", local:"myroot"). Expected elements are <{url1}myroot>和javax.xml.bind.UnmarshalException: unexpected element (uri:"url3", local:"myroot"). Expected elements are <{url1}myroot>

我的问题是:

有什么方法可以使此代码适用于不同的命名空间吗？

----------------------------------------------------------------

在 Blaise Doughan 的回答后进行编辑:

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由于我需要代码为每个输入的不同命名空间工作，因此我在代码中进行了以下更改:

1. 创建变量NAMESPACE在NamespaceFilter非静态。
2. 更改了Demo.java代码为MyRootUtils.java该方法名为 getMyRoot
3. 关于使用 JaxbContext.newInstance("url1")我发现没有这个newInstance()这需要 namespace-url作为一个论点。所以我把它改为:newInstance(Myroot.class) .
4. 更改了Test.java以适应新的类(class)。

MyRootUtils.java

package data.xml.jaxb.varns1;
import java.io.InputStream;
import javax.xml.bind.*;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.*;
public class MyRootUtils {
    public static MyRoot getMyRoot(String prefix,String url,InputStream xml) throws Exception {
        // Create the JAXBContext
        JAXBContext jc = JAXBContext.newInstance(MyRoot.class);//(MyRoot.class);
        // Create the XMLFilter
        XMLFilter filter = new NamespaceFilter(prefix,url);
        // Set the parent XMLReader on the XMLFilter
        filter.setParent(SAXParserFactory.newInstance().newSAXParser().getXMLReader());
        // Set UnmarshallerHandler as ContentHandler on XMLFilter
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        UnmarshallerHandler unmarshallerHandler = unmarshaller.getUnmarshallerHandler();
        filter.setContentHandler(unmarshallerHandler);
        // Parse the XML
        filter.parse(new InputSource(xml));
        return (MyRoot) unmarshallerHandler.getResult();
    }
}

命名空间过滤器.java

package data.xml.jaxb.varns1;
import org.xml.sax.*;
import org.xml.sax.helpers.XMLFilterImpl;
public class NamespaceFilter extends XMLFilterImpl {
    private final String NAMESPACE,PREFIX;
    public NamespaceFilter(String prefix,String url) {
        PREFIX=prefix;
        NAMESPACE=url;
    }
    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        System.out.println("::Into endElement(uri,localName,qName):: [uri: "+uri+"],[localName: "+localName+"],[qName: "+qName+"];");
        super.endElement(NAMESPACE, localName, qName);
    }
    @Override
    public void startElement(String uri, String localName, String qName,Attributes atts)
            throws SAXException {
        System.out.println("::Into startElement(uri,localName,qName,atts):: [uri: "+uri+"],[localName: "+localName+"],[qName: "+qName+"];");
        super.startElement(NAMESPACE, localName, qName, atts);
    }
    @Override
    public void startPrefixMapping(String prefix, String uri)
            throws SAXException {
        System.out.println(prefix+"="+uri);
        super.startPrefixMapping(PREFIX, NAMESPACE);
    }
    @Override
    public void endPrefixMapping(String prefix) throws SAXException {
        super.endPrefixMapping(PREFIX);
    }        
}

测试.java

package data.xml.jaxb.varns1;
import java.io.InputStream;    
public class Test {
    public static void main(String[]ar){
        String[] files={"input3.xml","input2.xml","input1.xml"};
        String[] urls ={"url3","url2","url1"};
        String[] prfs ={"","ns5","ns2"};
        for(int i = 0 ; i < 3 ; ++i){
            try{
                String prefix=prfs[i];
                String url = urls[i];
                InputStream xml = Test.class.getClassLoader().getResourceAsStream("data/xml/jaxb/varns1/"+files[i]);
                MyRoot myRoot = MyRootUtils.getMyRoot(prefix,url, xml);
                System.out.println(myRoot.getMyData().getMyRate());
            }catch (Exception e) {
                System.err.println(e.getCause());
            }
        }
    }
}

但是我仍然得到这个输出:

::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: myroot];
javax.xml.bind.UnmarshalException: unexpected element (uri:"url3", local:"myroot"). Expected elements are <{}myroot>
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns5:myroot];
javax.xml.bind.UnmarshalException: unexpected element (uri:"url2", local:"ns5:myroot"). Expected elements are <{}myroot>
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns2:myroot];
javax.xml.bind.UnmarshalException: unexpected element (uri:"url1", local:"ns2:myroot"). Expected elements are <{}myroot>

这意味着缺少了一些东西。

这是其中一个异常的完整堆栈跟踪(没有前缀的命名空间):

javax.xml.bind.UnmarshalException: unexpected element (uri:"url3", local:"myroot"). Expected elements are <{}myroot>
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:648)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:236)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:231)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:105)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1051)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:484)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:465)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.InterningXmlVisitor.startElement(InterningXmlVisitor.java:60)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:135)
    at org.xml.sax.helpers.XMLFilterImpl.startElement(XMLFilterImpl.java:527)
    at data.xml.jaxb.varns1.NamespaceFilter.startElement(NamespaceFilter.java:20)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
    at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidator.java:767)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1363)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$ContentDriver.scanRootElementHook(XMLDocumentScannerImpl.java:1315)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3104)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:921)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:647)
    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.xml.sax.helpers.XMLFilterImpl.parse(XMLFilterImpl.java:333)
    at data.xml.jaxb.varns1.MyRootUtils.getMyRoot(MyRootUtils.java:31)
    at data.xml.jaxb.varns1.Test.main(Test.java:15)
Caused by: javax.xml.bind.UnmarshalException: unexpected element (uri:"url3", local:"myroot"). Expected elements are <{}myroot>
    ... 27 more

这是另一个堆栈跟踪(带有前缀的命名空间):

javax.xml.bind.UnmarshalException: unexpected element (uri:"url2", local:"ns5:myroot"). Expected elements are <{}myroot>
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:648)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:236)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:231)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:105)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1051)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:484)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:465)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.InterningXmlVisitor.startElement(InterningXmlVisitor.java:60)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:135)
    at org.xml.sax.helpers.XMLFilterImpl.startElement(XMLFilterImpl.java:527)
    at data.xml.jaxb.varns1.NamespaceFilter.startElement(NamespaceFilter.java:20)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
    at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidator.java:767)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1363)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$ContentDriver.scanRootElementHook(XMLDocumentScannerImpl.java:1315)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3104)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:921)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:647)
    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.xml.sax.helpers.XMLFilterImpl.parse(XMLFilterImpl.java:333)
    at data.xml.jaxb.varns1.MyRootUtils.getMyRoot(MyRootUtils.java:31)
    at data.xml.jaxb.varns1.Test.main(Test.java:15)
Caused by: javax.xml.bind.UnmarshalException: unexpected element (uri:"url2", local:"ns5:myroot"). Expected elements are <{}myroot>
... 27 more

添加namespace="url1"也没有用，因为我仍然得到相同的异常堆栈。

输出:(没有 namespace="url1" )

::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns5:myroot];
javax.xml.bind.UnmarshalException: unexpected element (uri:"url2", local:"ns5:myroot"). Expected elements are <{}myroot>

输出:(带有 namespace="url1" )

::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns2:myroot];
javax.xml.bind.UnmarshalException: unexpected element (uri:"url1", local:"ns2:myroot"). Expected elements are <{url1}myroot>

显示 namespace 解析尚未完成。

最后，我做了另外 2 个更改:

1. 我使用了.replace("old-string","new-string")方法String类(class) NamespaceFilter.java减少qName (完全限定的元素名称)，如下所示:

   super.endElement(NAMESPACE, localName, qName);

   更改为:

   super.endElement("", localName, qName.replace(PREFIX+":", ""));

2. super.startElement(NAMESPACE, localName, qName, atts);

   更改为:

   super.startElement("", localName, qName.replace(PREFIX+":", ""), atts);

代码 NamespaceFilter.java :

package data.xml.jaxb.varns1;
import org.xml.sax.*;
import org.xml.sax.helpers.XMLFilterImpl;
public class NamespaceFilter extends XMLFilterImpl {
    private final String NAMESPACE,PREFIX;
    public NamespaceFilter(String prefix,String url) {
        PREFIX=prefix;
        NAMESPACE=url;
    }
    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        System.out.println("::Into endElement(uri,localName,qName):: [uri: "+uri+"],[localName: "+localName+"],[qName: "+qName+"];");
        super.endElement("", localName, qName.replace(PREFIX+":", ""));
    }
    @Override
    public void startElement(String uri, String localName, String qName,Attributes atts)
            throws SAXException {
        System.out.println("::Into startElement(uri,localName,qName,atts):: [uri: "+uri+"],[localName: "+localName+"],[qName: "+qName+"];");
        super.startElement("", localName, qName.replace(PREFIX+":", ""), atts);
    }
    @Override
    public void startPrefixMapping(String prefix, String uri)
            throws SAXException {
        System.out.println(prefix+"="+uri);
        super.startPrefixMapping(PREFIX, NAMESPACE);
    }
    @Override
    public void endPrefixMapping(String prefix) throws SAXException {
        super.endPrefixMapping(PREFIX);
    }
}

现在的输出是:

::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: myroot];
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: mydata];
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: myrate];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: myrate];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: mydata];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: myroot];
USD 955.25
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns5:myroot];
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns5:mydata];
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns5:myrate];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: ns5:myrate];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: ns5:mydata];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: ns5:myroot];
THB 1000.70
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns2:myroot];
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns2:mydata];
::Into startElement(uri,localName,qName,atts):: [uri: ],[localName: ],[qName: ns2:myrate];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: ns2:myrate];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: ns2:mydata];
::Into endElement(uri,localName,qName):: [uri: ],[localName: ],[qName: ns2:myroot];
GBP 800.55

但是，这引起了一些担忧:

1. 完全忽略命名空间。
2. 调用 String.replace()每次都有startElement() & endElement()

这让我思考这种变量命名空间方法是否应该可以接受。如果可以采取任何措施来改进此代码，那么我请求社区在答案/评论中提及它，并帮助消除这种可能有缺陷的方法。

Answer 1

处理主命名空间中的 XML

对于任何直接对应于您在 Java 模型中映射到的命名空间的 XML，您可以正常地编码/取消编码它

处理辅助命名空间中的 XML

解码

您可以在解码时应用 SAX XMLFilter，当您处理与具有命名空间 url2 的架构相对应的 XML 文档时，它看起来就像与具有命名空间 url1 的架构相对应。

import org.xml.sax.*;
import org.xml.sax.helpers.XMLFilterImpl;

public class NamespaceFilter extends XMLFilterImpl {

    private static final String NAMESPACE = "url1";

    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        super.endElement(NAMESPACE, localName, qName);
    }

    @Override
    public void startElement(String uri, String localName, String qName,
            Attributes atts) throws SAXException {
        super.startElement(NAMESPACE, localName, qName, atts);
    }

}

演示代码

以下是一些示例代码，演示如何应用 XMLFilter。

import javax.xml.bind.*;
import javax.xml.parsers.*;
import org.xml.sax.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        // Create the JAXBContext
        JAXBContext jc = JAXBContext.newInstance("url1");

        // Create the XMLFilter
        XMLFilter filter = new NamespaceFilter();

        // Set the parent XMLReader on the XMLFilter
        SAXParserFactory spf = SAXParserFactory.newInstance();
        SAXParser sp = spf.newSAXParser();
        XMLReader xr = sp.getXMLReader();
        filter.setParent(xr);

        // Set UnmarshallerHandler as ContentHandler on XMLFilter
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        UnmarshallerHandler unmarshallerHandler = unmarshaller
                .getUnmarshallerHandler();
        filter.setContentHandler(unmarshallerHandler);

        // Parse the XML
        InputSource xml = new InputSource("input.xml");
        filter.parse(xml);
        Object result = unmarshallerHandler.getResult();
    }

}