Question

In the XML example below, using a java parser how to keep the content under the tag AND followed by center and remove everything else?
The tag might have other instances when is followed by other tags than center, and those has to be discarded.

<xml>
    <A> 
        <B>
        .
        .
        .

            <parameter>
                <parameterid>center</parameterid>
                <name>Center</name>
                <keyframe>
                    <when>1</when>
                    <value>
                        <horiz>100</horiz>
                        <vert>100</vert>
                    </value>
                </keyframe>
                <keyframe>
                <when>2</when>
                    <value>
                        <horiz>150</horiz>
                        <vert>150</vert>
                    </value>
                </keyframe>
            </parameter>
            <parameter>
                ...
            </parameter>
            <parameter>
                ...
            </parameter>
        .
        .
        .
        </B>
    </A>
</xml>

So the output will look like:

<parameter>
    <parameterid>center</parameterid>
    <name>Center</name>
    <keyframe>
        <when>1</when>
        <value>
            <horiz>100</horiz>
            <vert>100</vert>
        </value>
    </keyframe>
    <keyframe>
    <when>2</when>
        <value>
            <horiz>150</horiz>
            <vert>150</vert>
        </value>
    </keyframe>
</parameter>

Please advise. Thanks!

Answer 1

You can use Java Regexp to remove unneeded content, and then parse only needed part f.e.

String sourceXML = readFileToString("source.xml")
final Pattern pattern = Pattern.compile(".*(<parameter>.+</parameter>).*",Pattern.DOTALL);
Matcher matcher = pattern.matcher(sourceXML);
if (matcher.find()) {
   String xmlToParse = matcher.group(0);
   someDomOrSaxParser.parseFromString(xmlToParse)
}else 
   System.out.println("NO MATCH");