如何让java XMLStreamReader能发出CDATA事件

最新推荐文章于 2024-11-11 11:50:39 发布

原创最新推荐文章于 2024-11-11 11:50:39 发布 · 770 阅读

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要对一个带CDATA的XML文档的某些element内容加密，加密后除了被加密的element外，其他内容不能变。这个需求看起来比较简单，为了有比较好的性能，用了java XML stream API。先看看能否把一个XML文档由XMLStreamReader读出，再由XMLStreamWriter写入新的XML文件。代码比较简单：

import javax.xml.stream.*;
import java.io.StringWriter;
import java.io.FileReader;

public class XMLStreamWriterTest {
    public static void main(String...args ) throws Exception {
        XMLInputFactory inputFactory = XMLInputFactory.newInstance();
        XMLStreamReader streamReader = inputFactory.createXMLStreamReader( new FileReader( args[0] ) );

        XMLOutputFactory outputFactory = XMLOutputFactory.newInstance();
        StringWriter writer = new StringWriter();
        XMLStreamWriter streamWriter = outputFactory.createXMLStreamWriter( writer );
        StringBuilder content = new StringBuilder();

        while (streamReader.hasNext()) {
            switch( streamReader.next() ) {
                    case XMLStreamConstants.START_ELEMENT:
                        if( content.length() > 0 ) {
                            streamWriter.writeCharacters( content.toString() );
                        }
                        content.setLength( 0 );
                        streamWriter.writeStartElement( streamReader.getLocalName() );

                        //write the attribute
                        for( int i = 0, n = streamReader.getAttributeCount(); i < n; i++ ) {
                            streamWriter.writeAttribute(streamReader.getAttributeLocalName(i),streamReader.getAttributeValue(i));
                        }
                        break;
                    case XMLStreamConstants.END_ELEMENT:
                        if( content.length() > 0 ) {
                            streamWriter.writeCharacters( content.toString());
                            content.setLength(0);
                        }
                        streamWriter.writeEndElement();
                        break;
                    case XMLStreamConstants.SPACE:
                    case XMLStreamConstants.CHARACTERS:
                        content.append( streamReader.getText() );
                        break;
                    case XMLStreamConstants.CDATA:
                        streamWriter.writeCData( streamReader.getText());
                        break;
                    case XMLStreamConstants.ENTITY_REFERENCE:
                        streamWriter.writeEntityRef( streamReader.getText());
                        break;
                    case XMLStreamConstants.COMMENT:
                        streamWriter.writeComment( streamReader.getText());
                        break;
                    case XMLStreamConstants.DTD:
                        streamWriter.writeDTD( streamReader.getText());
                        break;
            }
        }
        System.out.println( writer );
    }
}

用文件Test1.xml测试一下，Test1.xml的内容如下：

<Element1>
    <Child1>this is first child</Child1>
    <Child2>this is second child</Child2>
</Element1>

$ java -cp . XMLStreamWriterTest Test1.xml

输出：

<Element1>
    <Child1>this is first child</Child1>
    <Child2>this is second child</Child2>
</Element1>

完全一样。

再用带CDATA的XML文件Test2.xml测试一下, Test2.xml的内容如下：

<Element1>
    <Child1>this is first child</Child1>
    <Child2><![CDATA[this is second child]]></Child2>
</Element1>

$ java -cp . XMLStreamWriterTest Test2.xml

输出：

<Element1>
    <Child1>this is first child</Child1>
    <Child2>this is second child</Child2>
</Element1>

给想要的结果不一样。怎么回事？上网查了一下，方法如下：

1）需要将inputFactor中的属性javax.xml.stream.isCoalescing设置为false

2）需要将inputFactory中的属性"http://java.sun.com/xml/stream/properties/report-cdata-event"设置为true

修改代码：

import javax.xml.stream.*;
import java.io.StringWriter;
import java.io.FileReader;

public class XMLStreamWriterTest {
    public static void main(String...args ) throws Exception {
        XMLInputFactory inputFactory = XMLInputFactory.newInstance();
        inputFactory.setProperty( XMLInputFactory.IS_COALESCING,  Boolean.FALSE );
        inputFactory.setProperty( "http://java.sun.com/xml/stream/properties/report-cdata-event", Boolean.TRUE );
        XMLStreamReader streamReader = inputFactory.createXMLStreamReader( new FileReader( args[0] ) );

        XMLOutputFactory outputFactory = XMLOutputFactory.newInstance();
        StringWriter writer = new StringWriter();
        XMLStreamWriter streamWriter = outputFactory.createXMLStreamWriter( writer );
        StringBuilder content = new StringBuilder();

        while (streamReader.hasNext()) {
            switch( streamReader.next() ) {
                    case XMLStreamConstants.START_ELEMENT:
                        if( content.length() > 0 ) {
                            streamWriter.writeCharacters( content.toString() );
                        }
                        content.setLength( 0 );
                        streamWriter.writeStartElement( streamReader.getLocalName() );

                        //write the attribute
                        for( int i = 0, n = streamReader.getAttributeCount(); i < n; i++ ) {
                            streamWriter.writeAttribute(streamReader.getAttributeLocalName(i),streamReader.getAttributeValue(i));
                        }
                        break;
                    case XMLStreamConstants.END_ELEMENT:
                        if( content.length() > 0 ) {
                            streamWriter.writeCharacters( content.toString());
                            content.setLength(0);
                        }
                        streamWriter.writeEndElement();
                        break;
                    case XMLStreamConstants.SPACE:
                    case XMLStreamConstants.CHARACTERS:
                        content.append( streamReader.getText() );
                        break;
                    case XMLStreamConstants.CDATA:
                        streamWriter.writeCData( streamReader.getText());
                        break;
                    case XMLStreamConstants.ENTITY_REFERENCE:
                        streamWriter.writeEntityRef( streamReader.getText());
                        break;
                    case XMLStreamConstants.COMMENT:
                        streamWriter.writeComment( streamReader.getText());
                        break;
                    case XMLStreamConstants.DTD:
                        streamWriter.writeDTD( streamReader.getText());
                        break;
            }
        }
        System.out.println( writer );
    }
}

再运行一次：

$ java -cp . XMLStreamWriterTest Test2.xml

结果如下：

<Element1>
    <Child1>this is first child</Child1>
    <Child2><![CDATA[this is second child]]></Child2>
</Element1>

结果符合预期。