使用Web服务从xml文档中获取数据时，出现空指针异常

Question

String name= "Nsss";
String resulturl ="http://ssss/res/get?sid="+name+"";



DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(resulturl));
Document doc = db.parse(resulturl);
System.out.println("sssssssssssssssssssssssssssssssssssssssssssssssssss"+doc.getDoctype().getTextContent());

I am getting this exception.

java.lang.NullPointerException at com.controller.StudentsResultsController.main(ResultsController.java:130)

Answer 1

You should check to see what the resulturl variable is before you use it, but the other thing you need to address is: You are not using the InputSource at all. The following is likely to work better than what you have:

InputSource is = new InputSource();
is.setCharacterStream(new StringReader(resulturl));
Document doc = db.parse(is);

EDIT

The Fatal Error is caused by the following:

StringReader(resulturl) takes a string argument that must be XML, not a filename or a URL. The parser is reading the value of the string variable, resulturl, and failing immediately because an XML document may not begin with an h character.

Try changing the above to:

DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();          
Document doc = dBuilder.parse(new InputSource(resulturl));