Java：如何使用 stax 从 xml 中获取特定信息

Question

I am having trouble with getting specific information from my xml using stax. Inside my xml I have a current and average which both have a traveltime inside them. But I only want to get the traveltime from the current and not from the average. Here is how my xml looks like:

<allroutes>
    <routes>    
        <route identification="id_1">
            <current>
                <traveltime time="1187" trustworthy="j" />
                <delay time="0" trustworthy="j" />
            </current>
            <average>
                <traveltime time="1187" trustworthy="j" />
                <delay time="0" trustworthy="j" />
            </average>
        </route>
        <route identification="id_2">
            <current>
                <traveltime time="995" trustworthy="j" />
                <delay time="0" trustworthy="j" />
            </current>
            <average>
                <traveltime time="995" trustworthy="j" />
                <delay time="0" trustworthy="j" />
            </average>
        </route>
    </routes>
    <subpaths>
        <subpath identification="id_1">
            <current>
                <traveltime time="0" trustworthy="n" />
                <delay time="0" trustworthy="n" />
            </current>
            <average>
                <traveltime time="0" trustworthy="n" />
                <delay time="0" trustworthy="n" />
            </average>
        </subpath>
        <subpath identification="id_2">
            <current>
                <traveltime time="0" trustworthy="n" />
                <delay time="0" trustworthy="n" />
            </current>
            <average>
                <traveltime time="0" trustworthy="n" />
                <delay time="0" trustworthy="n" />
            </average>
        </subpath>
    </subpaths>
</allroutes>

The code that I have currently looks like this:

try{
    while (streamReader.hasNext()) {
        streamReader.next();
        if (streamReader.getEventType() == XMLStreamReader.START_ELEMENT) {

            switch (streamReader.getLocalName()) {
            case "route":
                //store which type
                break;
            case "subpath":
                //store which type
                break;
            case "traveltime":
                //store traveltime
                break;
            }
        }

        if (streamReader.getEventType() == XMLStreamReader.END_ELEMENT && "allroutes".equals(streamReader.getLocalName())) {

            //stop the loop and give back the object
        }
    }
}catch(XMLStreamException ex) {
    LOGGER.log(Level.SEVERE, "XMLStreamException: " + ex);
}

What do I need to add / change to only get the traveltime from 'current' inside this reader?

Answer 1

You just have to keep track of where you are in the document. For example, it's common practice to keep a stack of element names: push a name onto the stack when you hit a startElement, pop it off when you hit endElement, and then inspect the stack to discover the context of the element you are currently processing.