java code and SAX

[J amodi]

Hi all,

I am having one xml file which has contents something like this.

<studentTree>
<student id="1">
<name>jason</name>
<subject>Maths</subject>
<subject>Chemistry></subject>
<student>
<student id="2">
<name>John</name>
<subject>Science</subject>
<subject>History</subject>
<student>
</studentTree>

I am parsing this XML using SAX parser. I have written a code something like this.

public class SaxHandler extends DefaultHandler {

	boolean subjectCheck;
	boolean linksFrom;
	private StudentInfo studentInfo;
	private StringBuffer subjectStr;


	int i = 0;

	public void startElement(String uri, String localName, String elementName,
			Attributes attrs) throws SAXParseException, SAXException {

		if ("page".equalsIgnoreCase(elementName)) {

			studentInfo = new StudentInfo();

			String value = attrs.getValue("id");

			System.out.println("idValue:" + value);

			studentInfo.setId(value);
		}

		if ("subject".equalsIgnoreCase(elementName)) {
			subjectCheck = true;
			subjectStr = new StringBuffer();
		}
		

		
	}

	public void characters(char[] ch, int start, int len) throws SAXException {

		try {
			// String str = new String(ch, start, len);

			if (subjectCheck ) {
				subjectStr.append(ch, start, len);
			}
			

		} catch (Exception e) {
			System.out.println("XML File hasn't any elements");
			e.printStackTrace();
		}
	}

	public void endDocument() throws SAXException {
		System.out.println("Object Values:");

		System.out.println("student Id: " + studentInfo.getId());
		System.out.println("subjects:" + studentInfo.getSubjects());
		

	}

	public void endElement(String uri, String localName, String name)
			throws SAXException {
		List tempToList = new ArrayList();
		

		if ("subject".equalsIgnoreCase(name)) {
			subjectCheck= false;
			System.out.println(subjectStr);
			tempToList.add(subjectStr);
			pageInfo.setSubjects(tempToList);
		}
		
		System.out.println("tempToList size:" + tempToList.size());
	}

}


class PageInfo {

	private String Id;
	private List<String> subjects;

// assume getters and setters

}

I want to get values from my xml into objects.
for example,

1st iteration
studentinfo.getId() should give me value :1
studentInfo.getSubjects() should give me : Maths,Chemistry

2nd iteration
Value:2
studentInfo.getSubjects() should give me : science,history.

The problem is, I am not able to get subject values in the list as the element name(subject) is same. Could anyone please help me out in this ?

[Tim Moores]

You shouldn't create a new StringBuffer each time a subject tag is encountered. You should create it exactly once, and then clear it each time a student tag is closed.

[g tsuji]

@Jasoncool Smith

[0] You have major typos in the xml. And then, you have not cleaned up the code StudentInfo or PageInfo class, you've to pick one and use consistently.

[1] Then apart from those, the logic of the sax parsing is clearly defective. Here is a major rewrite based on it (I pick PageInfo).

public class SaxHandler extends DefaultHandler {

    boolean subjectCheck;
    boolean linksFrom;
    //private StudentInfo studentInfo;
    private PageInfo pageInfo;
    private StringBuffer subjectStr;
    private List<String> tempToList;    //declared here
    int i = 0;

    public void startElement(String uri, String localName, String elementName, Attributes attrs) 
    throws SAXParseException, SAXException {
        if ("student".equalsIgnoreCase(elementName)) {    //student, not subject
            //studentInfo = new StudentInfo();
            pageInfo=new PageInfo();
            String value = attrs.getValue("id");
            System.out.println("idValue:" + value);
            //studentInfo.setId(value);
            pageInfo.setId(value);
			
           tempToList = new ArrayList<String>();    //set it up here
        }
        if ("subject".equalsIgnoreCase(elementName)) {
            subjectCheck = true;
            subjectStr = new StringBuffer();    //or consider what other said; just minor concern for me
        }
    }

    public void characters(char[] ch, int start, int len) throws SAXException {
        try {
            // String str = new String(ch, start, len);
            if (subjectCheck ) {
                subjectStr.append(ch, start, len);
            }
        } catch (Exception e) {
            System.out.println("XML File hasn't any elements");
            e.printStackTrace();
        }
    }

    public void endDocument() throws SAXException {
        /* none of these
        System.out.println("Object Values:");
        //System.out.println("student Id: " + studentInfo.getId());
        //System.out.println("subjects:" + studentInfo.getSubjects());
        System.out.println("student Id: " + pageInfo.getId());
        System.out.println("subjects:" + pageInfo.getSubjects());
        */
    }

    public void endElement(String uri, String localName, String name)
    throws SAXException {
        //List tempToList = new ArrayList();    //not setting up here, not so; set up above
        if ("subject".equalsIgnoreCase(name)) {
            subjectCheck= false;
            System.out.println(subjectStr);
            tempToList.add(subjectStr.toString());    //generic List
            //pageInfo.setSubjects(tempToList);    //not doing that here, not so
        }
        if ("student".equalsIgnoreCase(name)) {    //instead put all commented out above here
            pageInfo.setSubjects(tempToList);
            System.out.println("tempToList size:" + tempToList.size());
            System.out.println("Object Values:");
            System.out.println("student Id: " + pageInfo.getId());
            System.out.println("subjects:" + pageInfo.getSubjects());
        }
    }
}

[J amodi]

Hi g tsuji,

Thanks a lot for reply. Yea, I had some typos in the code. Sorry about that. Your answer resolved my problem.

Hi Tim Moores,

Thanks for your reply too.