reflectiondatabasefactory.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2006, University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.classfile;

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


/**
 * A generic database factory that tries to create the database
 * by (in order of preference)
 * 
 * <ol>
 * <li>Invoking a static <b>create</b> method </li>
 * <li>Invoking a no-arg constructor
 * </ol>
 * 
 * @author David Hovemeyer
 */
public class ReflectionDatabaseFactory<E> implements IDatabaseFactory<E> {
	private Class<E> databaseClass;

	public ReflectionDatabaseFactory(Class<E> databaseClass) {
		this.databaseClass = databaseClass;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.IDatabaseFactory#createDatabase()
	 */
	public E createDatabase() throws CheckedAnalysisException {
		E database;

		database = createUsingStaticCreateMethod();
		if (database != null) {
			return database;
		}

		database = createUsingConstructor();
		if (database != null) {
			return database;
		}

		throw new CheckedAnalysisException(
				"Could not find a way to create database " + databaseClass.getName());
	}

	/**
	 * Try to create the database using a static create() method.
	 * 
	 * @return the database, or null if there is no static create() method
	 * @throws CheckedAnalysisException 
	 */
	private E createUsingStaticCreateMethod() throws CheckedAnalysisException {
		Method createMethod;
		try {
			createMethod = databaseClass.getMethod("create", new Class[0]);
		} catch (NoSuchMethodException e) {
			return null;
		}

		if (!Modifier.isStatic(createMethod.getModifiers())) {
			return null;
		}

		if (createMethod.getReturnType() != databaseClass) {
			return null;
		}

		try {
			return (E) createMethod.invoke(null, new Object[0]);
		} catch (InvocationTargetException e) {
			throw new CheckedAnalysisException("Could not create " + databaseClass.getName(), e);
		} catch (IllegalAccessException e) {
			throw new CheckedAnalysisException("Could not create " + databaseClass.getName(), e);
		}
	}

	/**
	 * Try to create the database using a no-arg constructor.
	 * 
	 * @return the database, or null if there is no no-arg constructor
	 * @throws CheckedAnalysisException 
	 */
	private E createUsingConstructor() throws CheckedAnalysisException {
		Constructor<E> constructor;
		try {
			constructor = databaseClass.getConstructor(new Class[0]);
		} catch (NoSuchMethodException e) {
			return null;
		}

		try {
			return constructor.newInstance(new Object[0]);
		} catch (InstantiationException e) {
			throw new CheckedAnalysisException("Could not create " + databaseClass.getName(), e);
		} catch (IllegalAccessException e) {
			throw new CheckedAnalysisException("Could not create " + databaseClass.getName(), e);
		} catch (InvocationTargetException e) {
			throw new CheckedAnalysisException("Could not create " + databaseClass.getName(), e);
		}
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.classfile.IDatabaseFactory#registerWith(edu.umd.cs.findbugs.classfile.IAnalysisCache)
	 */
	public void registerWith(IAnalysisCache analysisCache) {
		analysisCache.registerDatabaseFactory(databaseClass, this);
	}

}