如何使用VTD-XML获得ONE元素的所有名称空间声明？

这是我在大型XML处理过程中使用的类。

一些注意事项：

• 任何元素，在使用来自这个元素，并从所有祖先
• 当元素<elem />是<elem xmlns="x" />兄弟姐妹，他们有不同的命名空间
• 处理XML是xmlns声明通常基于堆栈的

代码：

import java.util.Deque; 
import java.util.HashMap; 
import java.util.Iterator; 
import java.util.LinkedList; 
import java.util.Map; 
import javax.xml.namespace.QName; 
import org.springframework.util.xml.SimpleNamespaceContext; 
import com.ximpleware.NavException; 
import com.ximpleware.VTDNav; 
public class VtdXmlCurrentState 
{ 
    /* Stack of QName.toString()s for the elements of processed XML - each is a full path */ 
    private Deque<String> qnames = new LinkedList<String>(); 
    /* Stack of QName.toString()s for the elements - each is a single path element and doesn't contain "/" */ 
    private Deque<QName> names = new LinkedList<QName>(); 
    // current depth in input document, starting from -1 
    private int currentDepth = -1; 
    // stack of namespace contexts increased during xml depth-first VTD navigation */ 
    private Deque<SimpleNamespaceContext> namespaces = new LinkedList<SimpleNamespaceContext>(); 
    // a flag for optimizing the case when there are many sibling elements without any xmlns declarations 
    // the case: 
    // <el /> 
    // <el /> 
    // ... 
    // it allows to effectively manage the stack and properly handles the following case: 
    // <el xmlns="x" /> 
    // <el /> 
    // in which the second element should use NSContext from parent and not a copy of sibling's NSContext 
    private boolean lastNSContextsDifferent = false; 
    /** 
    * 
    */ 
    public VtdXmlCurrentState() 
    { 
     // first a context without any mapping 
     this.namespaces.push(new SimpleNamespaceContext()); 
     // first QName is "/" 
     this.qnames.push("/"); 
     this.names.push(null); 
    } 
    /** 
    * Name of the current element 
    * @return 
    */ 
    public QName currentElementName() 
    { 
     return this.names.peek(); 
    } 
    /** 
    * Returns parent and current path for VTDNav 
    * 
    * @param nav 
    * @return 
    * @throws NavException 
    */ 
    public String[] currentXPath(VTDNav nav) throws NavException 
    { 
     // we don't check the end - autopilot handles that 
     int depth = nav.getCurrentDepth(); 
     int idx = nav.getCurrentIndex(); 
     this.handleNamespaces(nav, depth); 
     // determining current XPath 
     // name of the current element (optimization, because we're that the token is START_ELEMENT) 
     String elName = nav.toRawString(nav.getTokenOffset(idx), nav.getTokenLength(idx) & 0xffff); 
     QName qName = null; 
     if (elName.contains(":")) { 
     String[] qname = elName.split(":"); 
     qName = new QName(this.namespaces.peek().getNamespaceURI(qname[0]), qname[1]); 
     } else { 
     qName = new QName(this.namespaces.peek().getNamespaceURI(""), elName); 
     } 
     // full name of the current element 
     StringBuilder sb = new StringBuilder(1024); 
     String fullName = null; 
     for (int i = 0; i <= this.currentDepth - depth; i++) { 
     this.qnames.pop(); 
     this.names.pop(); 
     } 
     fullName = sb.append(this.qnames.peek()).append(qName.toString()).append("/").toString(); 
     String parentName = this.qnames.peek(); 
     this.qnames.push(fullName); 
     this.names.push(qName); 
     this.currentDepth = depth; 
     return new String[] { parentName, fullName }; 
    } 
    /** 
    * Handling element's namespaces - if there are any xmlns[:x], we must create new NSContext 
    * 
    * @param nav 
    * @param depth 
    * @throws NavException 
    */ 
    private void handleNamespaces(VTDNav nav, int depth) throws NavException 
    { 
     // are there any ns declarations? 
     Map<String, String> _namespaces = null; 
     int index = nav.getCurrentIndex() + 1; 
     int total = nav.getTokenCount(); 
     while (index < total) { 
     int type = nav.getTokenType(index); 
     while (type == VTDNav.TOKEN_ATTR_NAME) { 
      // quickly skip non-xmlns attrs 
      index += 2; 
      type = nav.getTokenType(index); 
     } 
     if (type == VTDNav.TOKEN_ATTR_NS) { 
      String prefix = nav.toString(index).substring(5); 
      if (prefix.length() > 0) 
       prefix = prefix.substring(1); 
      String namespace = nav.toString(index + 1); 
      if (_namespaces == null) 
       _namespaces = new HashMap<String, String>(); 
      _namespaces.put(prefix, namespace); 
     } else if (type == VTDNav.TOKEN_ATTR_VAL) { 
     } else { 
      break; 
     } 
     index++; 
     } 
     if (_namespaces != null) { 
     // first remove (if necessary) previous contexts from the stack - even if new element is at the same level 
     // (not descendant - it's sibiling), remove old, push new 
     for (int i = 0; i <= this.currentDepth - depth; i++) 
      this.namespaces.pop(); 
     // for this element there's xmlns declaration - this element has different namespace context 
     // and it will be valid till the next descendant with xmlns 
     // previous context 
     SimpleNamespaceContext snc = this.namespaces.peek(); 
     // new ... 
     SimpleNamespaceContext newSnc = new SimpleNamespaceContext(); 
     // ... to which we'll copy previous declarations 
     for (Iterator<?> prefixes = snc.getBoundPrefixes(); prefixes.hasNext();) { 
      String pfx = (String)prefixes.next(); 
      newSnc.bindNamespaceUri(pfx, snc.getNamespaceURI(pfx)); 
     } 
     newSnc.bindNamespaceUri("", snc.getNamespaceURI("")); 
     // adding (overwriting!) new namespace mappings 
     newSnc.setBindings(_namespaces); 
     this.namespaces.push(newSnc); 
     this.lastNSContextsDifferent = true; 
     } else { 
     // current element doesn't define new namespaces - it gets them from parent element 
     // optimization - no new namesaces, the same level - we don't do anything! 
     // we only do something if we got a level up - we have to pop some ns contexts 
     for (int i = 0; i < this.currentDepth - depth; i++) 
      this.namespaces.pop(); 
     if (this.currentDepth > depth) { 
      // we went up and popped() too much ns contexts - we duplicate the most recent 
      this.namespaces.push(this.namespaces.peek()); 
     } else if (this.currentDepth < depth) { 
      // we went down - just copy 
      this.namespaces.push(this.namespaces.peek()); 
     } else { 
      // the same level 
      if (this.lastNSContextsDifferent) { 
       this.namespaces.pop(); 
       this.namespaces.push(this.namespaces.peek()); 
      } 
     } 
     this.lastNSContextsDifferent = false; 
     } 
    } 
} 

输入XML：

<?xml version="1.0" encoding="UTF-8"?> 
<set id="#1" xmlns="urn:test:1.0"> 
    <documents xmlns="urn:test:1.0"> 
     <doc xmlns="urn:test:1.1" /> 
     <doc /> 
     <doc xmlns="urn:test:1.2" /> 
    </documents> 
    <documents /> 
    <documents xmlns="" /> 
</set> 

使用类：

byte[] doc = FileCopyUtils.copyToByteArray(super.createResource("dom03.xml").getInputStream()); 
VTDGen vtd = new VTDGen(); 
vtd.setDoc(doc); 
vtd.parse(true); 
VTDNav nav = vtd.getNav(); 
AutoPilot ap = new AutoPilot(); 
ap.bind(nav); 
ap.selectElementNS("*", "*"); 
VtdXmlCurrentState cxp = new VtdXmlCurrentState(); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/", cxp.currentXPath(nav)[1]); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/{urn:test:1.0}documents/", cxp.currentXPath(nav)[1]); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/{urn:test:1.0}documents/{urn:test:1.1}doc/", cxp.currentXPath(nav)[1]); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/{urn:test:1.0}documents/{urn:test:1.0}doc/", cxp.currentXPath(nav)[1]); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/{urn:test:1.0}documents/{urn:test:1.2}doc/", cxp.currentXPath(nav)[1]); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/{urn:test:1.0}documents/", cxp.currentXPath(nav)[1]); 
ap.iterate(); 
assertEquals("/{urn:test:1.0}set/documents/", cxp.currentXPath(nav)[1]); 
assertFalse(ap.iterate());