Pretty-prints XML files. Shell script to process all files in a directory included.

run.sh

find ./Files -name '*.xml' -type f > files.tmp
cat files.tmp | while read line; do java XMLBeautifier "$line"; done
rm ./files.tmp

XMLBeautifier.java

import java.io.*;

/**
 * Pretty-prints XML files.
 *
 * @author Michael Camilleri
 */
public class XMLBeautifier {

  private static final String BR = System.getProperty("line.separator");

  /**
   * Start here
   *
   * @param args XML file name
   */
  public static void main(String[] args) {

    String fileName;
    if (args.length == 1) {
      fileName = args[0];
      XMLBeautifier xmlBeautifier = new XMLBeautifier();
      String xml = xmlBeautifier.readFile(fileName);
      if (xml != null && xmlBeautifier.isXML(xml)) {
        xml = xml.replaceAll("<", BR + "<").replaceAll(">", ">" + BR).replaceAll("(?m)^\\s+", "");
        xml = xmlBeautifier.indent(xml);
        xmlBeautifier.saveFile(fileName, xml);
      }
    } else {
      System.out.print("Usage: java XMLBeautifier <XML file>");
    }
  }

  /**
   * Returns a String with the contents of the file specified
   *
   * @param fileName The file name
   * @return The contents of the file
   */
  private String readFile(String fileName) {
    StringBuilder fileContents = null;
    BufferedReader reader = null;
    try {
      FileReader input = new FileReader(fileName);
      reader = new BufferedReader(input);
      String line;
      fileContents = new StringBuilder();
      while ((line = reader.readLine()) != null) {
        fileContents.append(line);
      }
      reader.close();
    } catch (FileNotFoundException e) {
      System.err.println("File " + fileName + " not found");
    } catch (IOException e) {
      System.err.println("Error reading file " + fileName);
      e.printStackTrace();
    } finally {
      if (reader != null) {
        try {
          reader.close();
        } catch (IOException ignored) {
        }
      }
    }
    String result = null;
    if (fileContents != null) {
      result = fileContents.toString();
    }
    return result;
  }

  /**
   * Saves the given XML text into the specified file
   *
   * @param fileName The name of the file to save into
   * @param xml      The XML to save
   */
  private void saveFile(String fileName, String xml) {
    BufferedWriter writer = null;
    try {
      FileWriter output = new FileWriter(fileName);
      writer = new BufferedWriter(output);
      writer.write(xml);
      writer.flush();
      writer.close();
    } catch (IOException e) {
      System.err.println("Error saving to " + fileName);
    } finally {
      if (writer != null) {
        try {
          writer.close();
        } catch (IOException ignored) {
        }
      }
    }
  }

  /**
   * Returns <code>true</code> if the given text starts with '<' and ends with '>',
   * <code>false</code> otherwise
   *
   * @param xml The text to test
   * @return True or false depending on whether the given text is XML
   */
  private boolean isXML(String xml) {
    boolean isXML = false;
    if (xml != null && xml.trim().startsWith("<") && xml.trim().endsWith(">")) {
      isXML = true;
    }
    return isXML;
  }

  /**
   * Indents the given XML
   *
   * @param xml Unindented XML
   * @return Indented XML
   */
  private String indent(String xml) {
    StringBuilder result = new StringBuilder();
    String[] lines = xml.split(BR);
    int tabCount = -1;
    for (String line : lines) {
      if (line.startsWith("</")) {
        tabCount--;
        line = addTabs(line, tabCount);
      } else if (line.startsWith("<")) {
        line = addTabs(line, tabCount);
        tabCount++;
      } else {
        line = addTabs(line, tabCount);
      }
      if (line.endsWith("/>")) {
        tabCount--;
      }
      result.append(line).append(BR);
    }
    return result.toString();
  }

  /**
   * Appends the specified number of tabs to the beginning of the given line
   *
   * @param line     The line
   * @param tabCount The number of tabs to add
   * @return A tabbed line
   */
  private String addTabs(String line, int tabCount) {
    if (tabCount > 0) {
      line = addTabs("\t" + line, --tabCount);
    }
    return line;
  }
}