In many cases, XML data contains special characters such as ampersands (&), less than (<), greater than (>), and quotation marks (“). These characters can cause issues if they are not properly encoded and handled while parsing the XML data. This blog post will guide you on how to handle special characters and encoding issues in XML data using Java DOM Parser.
Table of Contents
What is Java DOM Parser?
Java DOM (Document Object Model) Parser is a standard API for parsing XML documents in Java. It provides a way to manipulate XML documents by representing them as a tree structure of nodes. The Java DOM Parser allows developers to read, update, and create XML documents programmatically.
Handling special characters
XML has reserved characters that have special meanings, such as ampersands (&), less than (<), greater than (>), and quotation marks (“). These characters need to be encoded in order to be represented in XML correctly. The following table shows the special characters and their corresponding XML entities:
| Character | XML Entity |
|---|---|
| & | & |
| < | < |
| > | > |
| ” | " |
| ’ | ' |
When working with XML data using Java DOM Parser, you need to encode these special characters before parsing the XML document. Here’s an example of encoding special characters using the Apache Commons Lang library:
import org.apache.commons.lang3.StringEscapeUtils;
String xmlData = "<example>Special characters: & < > \" '</example>";
String encodedXmlData = StringEscapeUtils.escapeXml(xmlData);
In the above code, we use the StringEscapeUtils.escapeXml() method to encode the special characters in the XML data. The resulting encodedXmlData will have the special characters properly encoded.
Encoding issues
In addition to handling special characters, encoding issues may arise if the XML document uses a different character encoding than the default encoding of the Java application. To avoid encoding issues, you should specify the character encoding when reading or writing XML data.
When reading an XML document, specify the character encoding using the InputSource class:
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.w3c.dom.Document;
import javax.xml.parsers.DocumentBuilderFactory;
import org.xml.sax.InputSource;
File xmlFile = new File("example.xml");
InputStream inputStream = new FileInputStream(xmlFile);
InputStreamReader reader = new InputStreamReader(inputStream, "UTF-8");
InputSource inputSource = new InputSource(reader);
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(inputSource);
In the above code, we specify the character encoding as UTF-8 when creating the InputStreamReader and pass it to the InputSource object. This ensures that the XML data is read with the correct character encoding.
When writing an XML document, specify the character encoding using the Transformer class:
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
Document document = ...;
File outputFile = new File("output.xml");
OutputStream outputStream = new FileOutputStream(outputFile);
OutputStreamWriter writer = new OutputStreamWriter(outputStream, "UTF-8");
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
transformer.setOutputProperty("encoding", "UTF-8");
DOMSource source = new DOMSource(document);
StreamResult result = new StreamResult(writer);
transformer.transform(source, result);
In the above code, we specify the character encoding as UTF-8 when creating the OutputStreamWriter and pass it to the StreamResult object. Additionally, we set the output encoding of the Transformer to UTF-8 using the setOutputProperty() method. This ensures that the XML document is written with the correct character encoding.
Conclusion
When working with XML data in Java using the DOM Parser, it is important to properly handle special characters and encoding issues. By encoding special characters and specifying the character encoding when reading or writing XML data, you can avoid issues and ensure the integrity of the parsed XML documents.
By following the guidelines and examples provided in this blog post, you should now have a better understanding of how to handle special characters and encoding issues in XML data using Java DOM Parser.