GrammaticalStructureFactory.java

package edu.stanford.nlp.trees;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

import edu.stanford.nlp.util.Filter;

/**
 * A general factory for {@link GrammaticalStructure} objects.
 *
 * Uses reflection to create objects of any subclass of
 * {@link GrammaticalStructure}.
 *
 * @author Galen Andrew
 */
public class GrammaticalStructureFactory {

  private final Constructor con;
  private final Filter<String> puncFilter;
  private final HeadFinder hf;

  /**
   * Make a new GrammaticalStructureFactory that dispenses {@link GrammaticalStructure}
   * objects of the given specific type
   * @param name the fully qualified name of a subclass of GrammaticalStructure
   */
  public GrammaticalStructureFactory(String name) {
    this(name, null);
  }

  /**
   * Make a new GrammaticalStructureFactory that dispenses
   * {@link GrammaticalStructure} objects of the given specific type
   *
   * @param name the fully qualified name of a subclass of GrammaticalStructure
   * @param puncFilter A filter that returns false on punctuation words
   */
  public GrammaticalStructureFactory(String name, Filter<String> puncFilter) {
    this(name, puncFilter, null);
  }

  public GrammaticalStructureFactory(String name, Filter<String> puncFilter, HeadFinder hf) {
    Class c, t, f, h;
    try {
      c = Class.forName(name);
      if (!Class.forName("edu.stanford.nlp.trees.GrammaticalStructure").isAssignableFrom(c)) {
        throw new ClassNotFoundException();
      }
      t = Class.forName("edu.stanford.nlp.trees.Tree");
      f = Class.forName("edu.stanford.nlp.util.Filter");
      h = Class.forName("edu.stanford.nlp.trees.HeadFinder");
    } catch (ClassNotFoundException e) {
      throw new RuntimeException("Class " + name + " does not exist or does not extend edu.stanford.nlp.trees.GrammaticalStructure.", e);
    }

    try {
      if (puncFilter == null) {
        if (hf == null) {
          con = c.getConstructor(t);
        } else {
          con = c.getConstructor(t, h);
        }
      } else {
        if (hf == null) {
          con = c.getConstructor(t, f);
        } else {
          con = c.getConstructor(t, f, h);
        }
      }
      this.puncFilter = puncFilter;
      this.hf = hf;
    } catch (NoSuchMethodException e) {
      // this is impossible, given above exceptions
      throw new RuntimeException();
    }
  }

  /**
   * Vend a new {@link GrammaticalStructure} based on the given {@link Tree}.
   *
   * @param t the tree to analyze
   * @return a GrammaticalStructure based on the tree
   */
  public GrammaticalStructure newGrammaticalStructure(Tree t) {
    try {
      if (puncFilter == null) {
        if (hf == null) {
          return (GrammaticalStructure) con.newInstance(t);
        } else {
          return (GrammaticalStructure) con.newInstance(t, hf);
        }
      } else {
        if (hf == null) {
          return (GrammaticalStructure) con.newInstance(t, puncFilter);
        } else {
          return (GrammaticalStructure) con.newInstance(t, puncFilter, hf);
        }
      }
    } catch (InstantiationException e) {
      throw new RuntimeException("Cannot instantiate " + con.getDeclaringClass().getName(), e);
    } catch (IllegalAccessException e) {
      throw new RuntimeException(con.getDeclaringClass().getName() + "(Tree t) does not have public access", e);
    } catch (InvocationTargetException e) {
      throw new RuntimeException("Failed to invoke " + con, e);
    }
  }

}