I found this interesting problem last week. Run the program below. It s very simple, first create a dummy xml file, and read it with standard lib and write it back to a file.

Look through the generated gtest2.xml, you will see that it has some content that were come out of nowhere.

In my case, this is the sample of wrong section (the place vary on different machine).

<test>1924</test>
<test>1925</test>
<test>t&gt;24</test>
<test>1927</test>
<test>1928</test>
<test>1929</test>

This does not happen if I changed my xml version to 1.0. So something wrong with my code or jdk?

Here is the test code:

import java.io.File;
import java.io.PrintWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
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;

public class DocumentBuilderCheck {

    public static void main(String[] args) throws Exception {
        String filename = "/tmp/gtest.xml";
        generateXmlFile(filename, 2500);
        Document doc = readXmlFile(filename);

        String filename2 = "/tmp/gtest2.xml";
        writeDocument(doc, filename2);
    }

    private static void writeDocument(Document document, String filename) throws Exception {
        StreamResult streamResult = new StreamResult(filename);
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.METHOD, "xml");
        transformer.transform(new DOMSource(document), streamResult);
    }

    private static Document readXmlFile(String filename) throws Exception {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setNamespaceAware(true);
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document doc = db.parse(new File(filename));
        return doc;
    }

    private static void generateXmlFile(String filename, int total)
            throws Exception {
        File f = new File(filename);

        PrintWriter pw = new PrintWriter(f);
        pw.write("<?xml version="1.1" encoding="UTF-8"?>");
        pw.write("<main_tag>");
        for (int i = 0; i < total; i++) {
            pw.write("<test>" + String.format("%04d", i) + "</test>");
        }
        pw.write("</main_tag>");
        pw.close();
    }
}