proposal/sandbox/antlib/src/main/org/apache/tools/ant/TaskAdapter.java

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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
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 *    Alternately, this acknowlegement may appear in the software itself,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * 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
 * <http://www.apache.org/>.
 */

package org.apache.tools.ant;

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



/**
 *  Use introspection to "adapt" an arbitrary Bean ( not extending Task, but with similar
 *  patterns).
 *
 * @author costin@dnt.ro
 * @author j_a_fernandez@yahoo.com
 */
public class TaskAdapter extends Task implements RoleAdapter {

    Object proxy;

    /**
     * Checks a class, whether it is suitable to be adapted by TaskAdapter.
     *
     * Checks conditions only, which are additionally required for a tasks
     * adapted by TaskAdapter. Thus, this method should be called by
     * {@link Project#checkTaskClass}.
     *
     * Throws a BuildException and logs as Project.MSG_ERR for
     * conditions, that will cause the task execution to fail.
     * Logs other suspicious conditions with Project.MSG_WARN.
     */
    public static void checkTaskClass(final Class taskClass, final Project project) {
        // This code is for backward compatibility
        checkClass(taskClass, project);
    }

    /**
     * Checks a class, whether it is suitable to be adapted.
     *
     * Checks conditions only, which are additionally required for a tasks
     * adapted by TaskAdapter.
     *
     * Throws a BuildException and logs as Project.MSG_ERR for
     * conditions, that will cause the task execution to fail.
     * Logs other suspicious conditions with Project.MSG_WARN.
     */
    public static void checkClass(final Class taskClass, final Project project) {
        // don't have to check for interface, since then
        // taskClass would be abstract too.
        try {
            final Method executeM = taskClass.getMethod( "execute", null );
            // don't have to check for public, since
            // getMethod finds public method only.
            // don't have to check for abstract, since then
            // taskClass would be abstract too.
            if(!Void.TYPE.equals(executeM.getReturnType())) {
                final String message = "return type of execute() should be void but was \""+executeM.getReturnType()+"\" in " + taskClass;
                project.log(message, Project.MSG_WARN);
            }
        } catch(NoSuchMethodException e) {
            final String message = "No public execute() in " + taskClass;
            project.log(message, Project.MSG_ERR);
            throw new BuildException(message);
        }
    }

    /**
     * Do the execution.
     */
    public void execute() throws BuildException {
        Method setProjectM = null;
        try {
            Class c = proxy.getClass();
            setProjectM =
                c.getMethod( "setProject", new Class[] {Project.class});
            if(setProjectM != null) {
                setProjectM.invoke(proxy, new Object[] {project});
            }
        } catch (NoSuchMethodException e) {
            // ignore this if the class being used as a task does not have
            // a set project method.
        } catch( Exception ex ) {
            log("Error setting project in " + proxy.getClass(),
                Project.MSG_ERR);
            throw new BuildException( ex );
        }


        Method executeM=null;
        try {
            Class c=proxy.getClass();
            executeM=c.getMethod( "execute", new Class[0] );
            if( executeM == null ) {
                log("No public execute() in " + proxy.getClass(), Project.MSG_ERR);
                throw new BuildException("No public execute() in " + proxy.getClass());
            }
            executeM.invoke(proxy, null);
            return;
        } catch( InvocationTargetException ite ) {
            Throwable t = ite.getTargetException();
            if (t instanceof BuildException) {
                throw (BuildException) t;
            }
            throw new BuildException(t);
        } catch( Exception ex ) {
            log("Error in " + proxy.getClass(), Project.MSG_ERR);
            throw new BuildException( ex );
        }

    }

    /**
     * Set the target object class
     */
    public void setProxy(Object o) {
        this.proxy = o;
    }

    public Object getProxy() {
        return this.proxy ;
    }

    public void setId(String id) {}
}