src/main/org/apache/tools/ant/taskdefs/optional/jsp/compilers/CompilerAdapterFactory.java

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Ant", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
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 * 5. Products derived from this software may not be called "Apache"
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 * ====================================================================
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 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
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 */
package org.apache.tools.ant.taskdefs.optional.jsp.compilers;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Task;


/**
 * Creates the necessary compiler adapter, given basic criteria.
 *
 * @author <a href="mailto:jayglanville@home.com">J D Glanville</a>
 * @author Matthew Watson <a href="mailto:mattw@i3sp.com">mattw@i3sp.com</a>
 */
public class CompilerAdapterFactory {

    /** This is a singlton -- can't create instances!! */
    private CompilerAdapterFactory() {
    }

    /**
     * Based on the parameter passed in, this method creates the necessary
     * factory desired.
     *
     * The current mapping for compiler names are as follows:
     * <ul><li>jasper = jasper compiler (the default)
     * <li><i>a fully quallified classname</i> = the name of a jsp compiler
     * adapter
     * </ul>
     *
     * @param compilerType either the name of the desired compiler, or the
     * full classname of the compiler's adapter.
     * @param task a task to log through.
     * @throws BuildException if the compiler type could not be resolved into
     * a compiler adapter.
     */
    public static CompilerAdapter getCompiler( String compilerType, Task task ) 
        throws BuildException {
        /* If I've done things right, this should be the extent of the
         * conditional statements required.
         */
        if ( compilerType.equalsIgnoreCase("jasper") ) {
            return new JasperC();
        }
        return resolveClassName( compilerType );
    }

    /**
     * Tries to resolve the given classname into a compiler adapter.
     * Throws a fit if it can't.
     *
     * @param className The fully qualified classname to be created.
     * @throws BuildException This is the fit that is thrown if className
     * isn't an instance of CompilerAdapter.
     */
    private static CompilerAdapter resolveClassName( String className )
        throws BuildException {
        try {
            Class c = Class.forName( className );
            Object o = c.newInstance();
            return (CompilerAdapter) o;
        } catch ( ClassNotFoundException cnfe ) {
            throw new BuildException( className + " can\'t be found.", cnfe );
        } catch ( ClassCastException cce ) {
            throw new BuildException(className + " isn\'t the classname of "
                                     + "a compiler adapter.", cce);
        } catch ( Throwable t ) {
            // for all other possibilities
            throw new BuildException(className + " caused an interesting "
                                     + "exception.", t);
        }
    }

}