之前实现的一个版本：

这个版本中存一个问题：如果某一个节点的值是空的话，会换行输出结束标签，如：

<a>

</a>

某些场景下会要求节点内必须要有值，否则就应该输出为 <a/>（例如XBRL instance的schemaLink节点）。

 

新代码如下：

XMLPrettyFormatter:

1 import javax.xml.stream.XMLStreamException; 2  3 /** 4  * XML pretty formatter. 5  */ 6 public interface XMLPrettyFormatter { 7  8     enum NodeType { 9         ELEMENT, VALUE, NULL10     }11 12     String DEFAULT_INDENTION = "\t";13 14     void writeStartElementIndention() throws XMLStreamException;15 16     /**17      * @param blankValue18      *            True if the value is null of blank character.19      */20     void writeValueIndention(boolean blankValue) throws XMLStreamException;21 22     void writeEndElementIndention() throws XMLStreamException;23 24 }

DefaultPrettyFormatter:

1 import java.util.LinkedList; 2  3 import javax.xml.stream.XMLStreamException; 4  5 import org.codehaus.stax2.XMLStreamWriter2; 6  7 /** 8  * Default XML pretty formatter. 9  * 
     
      10  * 
      
Default intention is tab character "\t".
11  * 
      
The value display in the same line with which element it belongs to.
12  * 
      
If value is blank, don't use separate end tag.
13  * 
     
14  */15 public class DefaultPrettyFormatter implements XMLPrettyFormatter {16 17     private String indent = DEFAULT_INDENTION;18 19     private LinkedList
     
       stack = new LinkedList
      
       ();20 21     private XMLStreamWriter2 writer;22 23     public DefaultPrettyFormatter(XMLStreamWriter2 writer) {24         this.writer = writer;25     }26 27     public DefaultPrettyFormatter(XMLStreamWriter2 writer, String indent) {28         this.writer = writer;29         this.indent = indent;30     }31 32     @Override33     public void writeStartElementIndention() throws XMLStreamException {34         NodeType lastNode = stack.peek();35         if (lastNode != null && lastNode == NodeType.NULL) {36             stack.pop();37         }38         39         writeLineBreaker();40         for (int i = 0; i < stack.size(); ++i) {41             writeIndention();42         }43         44         stack.push(NodeType.ELEMENT);45 46         // default value node47         stack.push(NodeType.NULL);48     }49 50     @Override51     public void writeValueIndention(boolean blankValue) throws XMLStreamException {52         if (!blankValue) {53             // if value is not blank, pop default blank node first.54             stack.pop();55             stack.push(NodeType.VALUE);56         }57     }58 59     @Override60     public void writeEndElementIndention() throws XMLStreamException {61         NodeType lastNode = stack.pop();62         if (lastNode == NodeType.ELEMENT) {63             writeLineBreaker();64             for (int i = 0; i < stack.size(); ++i) {65                 writeIndention();66             }67         } else {68             // pop start element69             stack.pop();70         }71     }72 73     private void writeLineBreaker() throws XMLStreamException {74         writer.writeCharacters("\n");75     }76 77     private void writeIndention() throws XMLStreamException {78         writer.writeCharacters(indent.toCharArray(), 0, indent.length());79     }80 81 }