Ant example source code file (IsReference.java)

This example Ant source code file (IsReference.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Ant tags/keywords

buildexception, buildexception, class, class, condition, isreference, isreference, no, object, object, projectcomponent, reference, string

The IsReference.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.tools.ant.taskdefs.condition;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.ProjectComponent;
import org.apache.tools.ant.types.Reference;

/**
 * Condition that tests whether a given reference has been defined.
 *
 * <p>Optionally tests whether it is of a given type/class.

 *
 * @since Ant 1.6
 */
public class IsReference extends ProjectComponent implements Condition {
    private Reference ref;
    private String type;

    /**
     * Set the refid attribute.
     *
     * @param r a Reference value
     */
    public void setRefid(Reference r) {
        ref = r;
    }

    /**
     * Set the type attribute. This is optional attribute.
     *
     * @param type an ant component type name
     */
    public void setType(String type) {
        this.type = type;
    }

    /**
     * @return true if the reference exists and if type is set, if
     *              the reference is the same type
     * @exception BuildException if an error occurs
     */
    public boolean eval() throws BuildException {
        if (ref == null) {
            throw new BuildException("No reference specified for isreference "
                                     + "condition");
        }

        Object o = getProject().getReference(ref.getRefId());

        if (o == null) {
            return false;
        } else if (type == null) {
            return true;
        } else {
            Class typeClass =
                (Class) getProject().getDataTypeDefinitions().get(type);

            if (typeClass == null) {
                typeClass =
                    (Class) getProject().getTaskDefinitions().get(type);
            }

            if (typeClass == null) {
                // don't know the type, should throw exception instead?
                return false;
            }

            return typeClass.isAssignableFrom(o.getClass());
        }
    }

}