Java read xml file dom tutorial

The following code configures the document builder to use the error handler defined in Handle Errors. The code you have seen so far has set up the document builder, and configured it to perform validation upon request. Error handling is also in place. However, DOMEcho does not do anything yet.

In the next section, you will see how to display the DOM structure and begin to explore it. And perhaps most importantly, you will see how text nodes which contain the actual data reside under element nodes in a DOM.

This section of the tutorial exposes the internal structure of a DOM, so that you can see what it contains. The DOMEcho example does this by echoing the DOM nodes, and then printing them out onscreen, with the appropriate indentation to make the node hierarchy apparent. Table below is adapted from that specification. The information in this table is extremely useful; you will need it when working with a DOM, because all these types are intermixed in a DOM tree.

The DOM node element type information is obtained by calling the various methods of the org. Node class. The node attributes by exposed by DOMEcho are echoed by the following code. Every DOM node has at least a type, a name, and a value, which might or might not be empty.

Note that the trim method is called on the value returned by getNodeValue to establish whether the node's value is empty white space and print a message accordingly. For the full list of Node methods and the different information they return, see the API documentation for Node. Next, a method is defined to set the indentation for the nodes when they are printed, so that the node hierarchy will be easily visible.

The basicIndent constant to define the basic unit of indentation used when DOMEcho displays the node tree hierarchy, is defined by adding the following highlighted lines to the DOMEcho constructor class. Lexical information is the information you need to reconstruct the original syntax of an XML document. Preserving lexical information is important in editing applications, where you want to save a document that is an accurate reflection of the original-complete with comments, entity references, and any CDATA sections it may have included at the outset.

Most applications, however, are concerned only with the content of the XML structures. They can afford to ignore comments, and they do not care whether data was coded in a CDATA section or as plain text, or whether it included an entity reference. For such applications, a minimum of lexical information is desirable, because it simplifies the number and kind of DOM nodes that the application must be prepared to examine. The default values for all these properties is false, which preserves all the lexical information necessary to reconstruct the incoming document in its original form.

Setting them to true lets you construct the simplest possible DOM so that the application can focus on the data's semantic content without having to worry about lexical syntax details. Table summarizes the effects of the settings. The implementation of these methods in the main method of the DomEcho example is shown below. Note - Text nodes exist under element nodes in a DOM, and data is always stored in text nodes. Perhaps the most common error in DOM processing is to navigate to an element node and expect it to contain the data that is stored in that element.

Not so! Even the simplest element node has a text node under it that contains the data. This code first of all uses switch statements to print out the different node types and any possible child nodes, with the appropriate indentation. NodeList objects in the DOM are live. The items in the NodeList are accessible via an integral index, starting from 0. Element; import org. If the XML file is not accessible, then you will get java.

FileNotFoundException exception. Make sure the file is present in the location provided and the file name is correct. There could be many reasons you may get a NullPointerException operating on a null object! Popular Topics. ParserConfigurationException; Step 5: Create org. Document object using documentBuilder. Step 6: Create org. Reference: Official W3. ClassCastException: com. DeferredElementImpl cannot be cast to javax.

Nice program Pankaj…can u write one program to access multiple xml files. Can you please tell me what am I doing wrong? Can you please help me, as i run the above program it gives a java. NullPointerException at com. Could you help? Sorry forgot the xml earlier. Your email address will not be published.

Pankaj I love Open Source technologies and writing about my experience about them is my passion. Follow Author.

April 27, at pm.