available, instead of erroring out, the dependency result will be
                `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, in a query
                parameter or in an HTTP Bearer token).

package org.apache.maven.exception;

import java.util.Collections;
import java.util.List;

/**
 * Provide a summary of the exception, containing:<ul>
 * <li>the exception itself,</li>
 * <li>useful end-user message,</li>
 * <li>useful reference to a solution, or set of solutions: this is usually a wiki page url in
 * <a href="http://cwiki.apache.org/confluence/display/MAVEN/">http://cwiki.apache.org/confluence/display/MAVEN/</a>,
 * </li>

                is not available, instead of erroring out, the dependency result will
                be `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, with OpenID
                Connect or in a cookie).

// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 Affero General Public License for more details.
//

        But Guava aims to provide functionality that is useful across boundaries of projects,
        companies, or even industries — utilities useful for a sizable proportion of all Java
        programmers everywhere. If you can give enough detail such that any of us can imagine coming
        across a similar need in our own work, that's extremely helpful in studying how broadly
        useful the proposed change will be.

  - type: textarea

     */
    boolean required() default false;

    /**
     * Specifies that this parameter cannot be configured directly by the user (as in the case of POM-specified
     * configuration). This is useful when you want to force the user to use common POM elements rather than plugin
     * configurations, as in the case where you want to use the artifact's final name as a parameter. In this case, you

But still, it is very powerful, and allows you to declare arbitrarily deeply nested dependency "graphs" (trees).

!!! tip
    All this might not seem as useful with these simple examples.

    But you will see how useful it is in the chapters about **security**.

 *
 * <p>This class extends {@link Number}, but does not define methods such as {@code
 * equals}, {@code hashCode} and {@code compareTo} because instances are expected to be mutated, and
 * so are not useful as collection keys.
 *
 * <p>jsr166e note: This class is targeted to be placed in java.util.concurrent.atomic.
 *
 * @since 1.8
 * @author Doug Lea
 */
@GwtCompatible(emulated = true)

 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.exception;

/**
 * Transform an exception into useful end-user message.
 *
 * @since 3.0-alpha-3
 */
public interface ExceptionHandler {
    ExceptionSummary handleException(Throwable e);

 * 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.
 *