/*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* SnowballStemmer.java
* Copyright (C) 2005-2012 University of Waikato, Hamilton, New Zealand
*
*/
package weka.core.stemmers;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.Vector;
import weka.core.Option;
import weka.core.OptionHandler;
import weka.core.RevisionUtils;
import weka.core.Utils;
/**
* <!-- globalinfo-start --> A wrapper class for the Snowball stemmers. Only available if the Snowball classes are in the classpath.<br/>
* If the class discovery is not dynamic, i.e., the property 'UseDynamic' in the props file 'weka/gui/GenericPropertiesCreator.props' is 'false', then the property 'org.tartarus.snowball.SnowballProgram' in the 'weka/gui/GenericObjectEditor.props' file has to be uncommented as well. If necessary you have to discover and fill in the snowball stemmers manually. You can use the 'weka.core.ClassDiscovery' for this:<br/>
* java weka.core.ClassDiscovery org.tartarus.snowball.SnowballProgram org.tartarus.snowball.ext<br/>
* <br/>
* For more information visit these web sites:<br/>
* http://weka.wikispaces.com/Stemmers<br/>
* http://snowball.tartarus.org/<br/>
* <p/>
* <!-- globalinfo-end -->
*
* <!-- options-start --> Valid options are:
* <p/>
*
* <pre>
* -S <name>
* The name of the snowball stemmer (default 'porter').
* available stemmers:
* danish, dutch, english, finnish, french, german, italian,
* norwegian, porter, portuguese, russian, spanish, swedish
* </pre>
*
* <!-- options-end -->
*
* @author FracPete (fracpete at waikato dot ac dot nz)
* @version $Revision: 8034 $
*/
public class SnowballStemmer implements Stemmer, OptionHandler {
/** for serialization. */
static final long serialVersionUID = -6111170431963015178L;
/** the package name for snowball. */
public final static String PACKAGE = "org.tartarus.snowball";
/** the package name where the stemmers are located. */
public final static String PACKAGE_EXT = PACKAGE + ".ext";
/** the snowball program, all stemmers are derived from. */
protected final static String SNOWBALL_PROGRAM = PACKAGE + ".SnowballProgram";
/** whether the snowball stemmers are in the Classpath. */
protected static boolean m_Present = false;
/** contains the all the found stemmers (language names). */
protected static Vector<String> m_Stemmers;
/** the current stemmer. */
protected Object m_Stemmer;
/** the stem method. */
protected transient Method m_StemMethod;
/** the setCurrent method. */
protected transient Method m_SetCurrentMethod;
/** the getCurrent method. */
protected transient Method m_GetCurrentMethod;
/** check for Snowball statically (needs only to be done once) */
static {
checkForSnowball();
}
/**
* initializes the stemmer ("porter").
*/
public SnowballStemmer() {
this("porter");
initStemmers();
}
/**
* initializes the stemmer with the given stemmer.
*
* @param name
* the name of the stemmer
*/
public SnowballStemmer(String name) {
super();
setStemmer(name);
}
/**
* checks whether Snowball is present in the classpath.
*/
private static void checkForSnowball() {
try {
Class.forName(SNOWBALL_PROGRAM);
m_Present = true;
} catch (Exception e) {
m_Present = false;
}
}
/**
* Returns a string describing the stemmer.
*
* @return a description suitable for displaying in the explorer/experimenter gui
*/
public String globalInfo() {
return "A wrapper class for the Snowball stemmers. Only available if the " + "Snowball classes are in the classpath.\n" + "If the class discovery is not dynamic, i.e., the property 'UseDynamic' " + "in the props file 'weka/gui/GenericPropertiesCreator.props' is 'false', " + "then the property 'org.tartarus.snowball.SnowballProgram' in the " + "'weka/gui/GenericObjectEditor.props' file has to be uncommented " + "as well. If necessary you have to discover and fill in the snowball " + "stemmers manually. You can use the 'weka.core.ClassDiscovery' for this:\n" + " java weka.core.ClassDiscovery org.tartarus.snowball.SnowballProgram org.tartarus.snowball.ext\n" + "\n" + "For more information visit these web sites:\n" + " http://weka.wikispaces.com/Stemmers\n" + " http://snowball.tartarus.org/\n";
}
/**
* Returns an enumeration describing the available options.
*
* @return an enumeration of all the available options.
*/
public Enumeration listOptions() {
Vector<Option> result;
result = new Vector<Option>();
result.addElement(new Option("\tThe name of the snowball stemmer (default 'porter').\n" + "\tavailable stemmers:\n" + getStemmerList(65, "\t "), "S", 1, "-S <name>"));
return result.elements();
}
/**
* Parses the options.
* <p/>
*
* <!-- options-start --> Valid options are:
* <p/>
*
* <pre>
* -S <name>
* The name of the snowball stemmer (default 'porter').
* available stemmers:
* danish, dutch, english, finnish, french, german, italian,
* norwegian, porter, portuguese, russian, spanish, swedish
* </pre>
*
* <!-- options-end -->
*
* @param options
* the options to parse
* @throws Exception
* if parsing fails
*/
public void setOptions(String[] options) throws Exception {
String tmpStr;
tmpStr = Utils.getOption('S', options);
if (tmpStr.length() != 0)
setStemmer(tmpStr);
else
setStemmer("porter");
}
/**
* Gets the current settings of the classifier.
*
* @return an array of strings suitable for passing to setOptions
*/
public String[] getOptions() {
Vector<String> result;
result = new Vector<String>();
if (getStemmer() != null) {
result.add("-S");
result.add("" + getStemmer());
}
return (String[]) result.toArray(new String[result.size()]);
}
/**
* extracts the stemmer name form the classname.
*
* @param classname
* the full classname of the stemmer
* @return the name of the stemmer
*/
private static String getStemmerName(String classname) {
return classname.replaceAll(".*\\.", "").replaceAll("Stemmer$", "");
}
/**
* returns the full classname of the stemmer.
*
* @param name
* the name of the stemmer
* @return the full classname of the stemmer
* @see #PACKAGE_EXT
*/
private static String getStemmerClassname(String name) {
return PACKAGE_EXT + "." + name + "Stemmer";
}
/**
* retrieves the language names of the availabel stemmers.
*/
private static void initStemmers() {
Vector classnames;
int i;
if (m_Stemmers != null)
return;
m_Stemmers = new Vector<String>();
if (!m_Present)
return;
/*classnames = GenericObjectEditor.getClassnames(SNOWBALL_PROGRAM);
// try dynamic discovery if not in props file
if (classnames.size() == 0) {
classnames = ClassDiscovery.find(SNOWBALL_PROGRAM, PACKAGE_EXT);
for (i = 0; i < classnames.size(); i++)
m_Stemmers.add(getStemmerName(classnames.get(i).toString()));
}*/
}
/**
* returns whether Snowball is present or not, i.e. whether the classes are in the classpath or not
*
* @return whether Snowball is available
*/
public static boolean isPresent() {
return m_Present;
}
/**
* returns an enumeration over all currently stored stemmer names.
*
* @return all available stemmers
*/
public static Enumeration listStemmers() {
initStemmers();
return m_Stemmers.elements();
}
/**
* generates a comma list of the available stemmers.
*
* @param lineLength
* the max line length, before a linefeed is inserted (0 is unlimited)
* @param indention
* the indention of a line
* @return the generated list
*/
private static String getStemmerList(int lineLength, String indention) {
String result;
Enumeration enm;
String name;
String line;
result = "";
line = "";
enm = listStemmers();
while (enm.hasMoreElements()) {
name = enm.nextElement().toString();
if (line.length() > 0)
line += ", ";
if ((lineLength > 0) && (line.length() + name.length() > lineLength)) {
result += indention + line + "\n";
line = "";
}
line += name;
}
if (line.length() > 0)
result += indention + line + "\n";
return result;
}
/**
* returns the name of the current stemmer, null if none is set.
*
* @return the name of the stemmer
*/
public String getStemmer() {
initStemmers();
if (m_Stemmer == null)
return null;
else
return getStemmerName(m_Stemmer.getClass().getName());
}
/**
* sets the stemmer with the given name, e.g., "porter".
*
* @param name
* the name of the stemmer, e.g., "porter"
*/
public void setStemmer(String name) {
Class<?> snowballClass;
Class[] argClasses;
initStemmers();
if (m_Stemmers.contains(name)) {
try {
snowballClass = Class.forName(getStemmerClassname(name));
m_Stemmer = snowballClass.newInstance();
// methods
argClasses = new Class[0];
m_StemMethod = snowballClass.getMethod("stem", argClasses);
argClasses = new Class[1];
argClasses[0] = String.class;
m_SetCurrentMethod = snowballClass.getMethod("setCurrent", argClasses);
argClasses = new Class[0];
m_GetCurrentMethod = snowballClass.getMethod("getCurrent", argClasses);
} catch (Exception e) {
System.out.println("Error initializing stemmer '" + name + "'!" + e.getMessage());
m_Stemmer = null;
}
} else {
System.err.println("Stemmer '" + name + "' unknown!");
m_Stemmer = null;
}
}
/**
* Returns the tip text for this property.
*
* @return tip text for this property suitable for displaying in the explorer/experimenter gui
*/
public String stemmerTipText() {
return "The Snowball stemmer to use, available: " + getStemmerList(0, "");
}
/**
* Returns the word in its stemmed form.
*
* @param word
* the unstemmed word
* @return the stemmed word
*/
public String stem(String word) {
String result;
Object[] args;
if (m_Stemmer == null) {
result = new String(word);
} else {
// after de-serialization, the methods are null and need to be
// re-initialized
if (m_SetCurrentMethod == null)
setStemmer(getStemmer());
try {
// set word
args = new Object[1];
args[0] = word;
m_SetCurrentMethod.invoke(m_Stemmer, args);
// stem word
args = new Object[0];
m_StemMethod.invoke(m_Stemmer, args);
// get word
args = new Object[0];
result = (String) m_GetCurrentMethod.invoke(m_Stemmer, args);
} catch (Exception e) {
e.printStackTrace();
result = word;
}
}
return result;
}
/**
* returns a string representation of the stemmer.
*
* @return a string representation of the stemmer
*/
public String toString() {
String result;
result = getClass().getName();
result += " " + Utils.joinOptions(getOptions());
return result.trim();
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 8034 $");
}
/**
* Runs the stemmer with the given options.
*
* @param args
* the options
*/
public static void main(String[] args) {
try {
Stemming.useStemmer(new SnowballStemmer(), args);
} catch (Exception e) {
e.printStackTrace();
}
}
}