Android: Parsing XML DOM parser. Converting childnodes to string_问答_开发者

Again a question. This time I'm parsing XML messages I receive from a server. Someone thought to be smart and decided to place HTML pages in a XML message. Now I'm kind of facing problems because I want to extract that HTML page as a string from this XML message.

Ok this is the XML message I'm parsing:

<AmigoRequest> <From></From> <To></To> <MessageType>showMessage</MessageType> <Param0>general message</Param0> <Param1><html><head>test</head><body>Testhtml</body></html></Param1> </AmigoRequest>

You see that in Param1 a HTML page is specified. I've tried to extract the message the following way:

public String getParam1(Document d) {
        if (d.getDocumentElement().getTagName().equals("AmigoRequest")) {
            Nod开发者_高级运维eList results = d.getElementsByTagName("Param1");
            // Messagetype depends on what message we are reading.           
            if (results.getLength() > 0 && results != null) {                
                return results.item(0).getFirstChild().getNodeValue();
            }
        }
        return "";
    }

Where d is the XML message in document form. It always returns me a null value, because getNodeValue() returns null. When i try results.item(0).getFirstChild().hasChildNodes() it will return true because he sees there is a tag in the message.

How can i extract the html message <html><head>test</head><body>Testhtml</body></html> from Param0 in a string?

I'm using Android sdk 1.5 (well almost java) and a DOM Parser.

Thanks for your time and replies.

Antek

You could take the content of param1, like this:

public String getParam1(Document d) {
        if (d.getDocumentElement().getTagName().equals("AmigoRequest")) {
            NodeList results = d.getElementsByTagName("Param1");
            // Messagetype depends on what message we are reading.           
            if (results.getLength() > 0 && results != null) {                

                // String extractHTMLTags(String s) is a function that you have 
                // to implement in a way that will extract all the HTML tags inside a string.
                return extractHTMLTags(results.item(0).getTextContent());
            }
        }
        return "";
    }

All you have to do is to implement a function:

String extractHTMLTags(String s)

that will remove all HTML tag occurrences from a string. For that you can take a look at this post: Remove HTML tags from a String

after checking a lot and scratching my head thousands of times I came up with simple alteration that it needs to change your API level to 8

EDIT: I just saw your comment above about getTextContent() not being supported on Android. I'm going to leave this answer up in case it's useful to someone who's on a different platform.

If your DOM API supports it, you can call getTextContent(), as follows:

public String getParam1(Document d) {
        if (d.getDocumentElement().getTagName().equals("AmigoRequest")) {
            NodeList results = d.getElementsByTagName("Param1");
            // Messagetype depends on what message we are reading.           
            if (results != null) {                
                return results.getTextContent();
            }
        }
        return "";
    }

However, getTextContent() is a DOM Level 3 API call; not all parsers are guaranteed to support it. Xerces-J does.

By the way, in your original example, your check for null is in the wrong place; it should be:

        if (results != null && results.getLength() > 0) {

Otherwise, you'd get a NPE if results really does come back as null.

Since getTextContent() isn't available to you, another option would be to write it -- it isn't hard. In fact, if you're writing this solely for your own use -- or your employer doesn't have overly strict rules about open source -- you could look at Apache's implementation as a starting point; lines 610-646 seem to contain most of what you need. (Please be respectful of Apache's copyright and license.)

Otherwise, some rough pseudocode for the method would be:

String getTextContent(Node node) {
    if (node has no children) 
        return "";

    if (node has 1 child)
        return getTextContent(node.getFirstChild());

    return getTextContent(new StringBuffer()).toString();
}

StringBuffer getTextContent(Node node, StringBuffer sb) {
    for each child of node {
        if (child is a text node) sb.append(child's text)
        else getTextContent(child, sb);
    }
    return sb;
}

Well i was almost there with the code...

public String getParam1(Document d) {
    if (d.getDocumentElement().getTagName().equals("AmigoRequest")) {
        NodeList results = d.getElementsByTagName("Param1");
        // Messagetype depends on what message we are reading.           
        if (results.getLength() > 0 && results != null) {                
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db;
            Element node = (Element) results.item(0); // get the value of Param1
            Document doc2 = null;
            try {

                db = dbf.newDocumentBuilder();
                doc2 = db.newDocument(); //create new document
                doc2.appendChild(doc2.importNode(node, true)); //import the <html>...</html> result in doc2

            } catch (ParserConfigurationException e) {
                // TODO Auto-generated catch block
                Log.d(TAG, " Exception ", e);
            } catch (DOMException e) {
                // TODO: handle exception
                Log.d(TAG, " Exception ", e);
            } catch (Exception e) {
                // TODO: handle exception
                e.printStackTrace();               }              


            return doc2. .....// All I'm missing is something to convert a Document to a string.
        }
    }
    return "";

}

Like explained in the comment of my code. All I am missing is to make a String out of a Document. You can't use the Transform class in Android... doc2.toString() will give you a serialization of the object..

But my next step is write my own parser if this doesnt work out ;)

Not the best code but a temponary solution.

public String getParam1(String b) {
        return b
                .substring(b.indexOf("<Param1>") + "<Param1>".length(), b.indexOf("</Param1>"));
    }

Where String b is the XML document string.