juneau-core/juneau-marshall/src/main/java/org/apache/juneau/internal/ExceptionBuilder.java

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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.internal;

import static org.apache.juneau.internal.ExceptionUtils.*;
import static org.apache.juneau.internal.StringUtils.*;

/**
 * Builder class for {@link Exception} objects.
 *
 * @param <T> The exception class.
 */
public class ExceptionBuilder<T extends Throwable> {

	private final Class<T> type;
	private String message;
	private Throwable causedBy;

	/**
	 * Default constructor.
	 * @param type The exception type to create.
	 */
	public ExceptionBuilder(Class<T> type) {
		this.type = type;
	}

	/**
	 * Specifies the exception message.
	 *
	 * @param msg The exception message.  Can be <jk>null</jk>.
	 * 	<br>If <jk>null</jk>, then the caused-by message is used if available.
	 * @param args The exception message arguments.
	 * @return This object (for method chaining).
	 */
	@FluentSetter
	public ExceptionBuilder<T> message(String msg, Object...args) {
		message = format(msg, args);
		return this;
	}

	/**
	 * Specifies the caused-by exception.
	 *
	 * @param value The caused-by exception.  Can be <jk>null</jk>.
	 * @return This object (for method chaining).
	 */
	@FluentSetter
	public ExceptionBuilder<T> causedBy(Throwable value) {
		causedBy = value;
		return this;
	}

	/**
	 * Creates the exception.
	 *
	 * @return The exception.
	 */
	public T build() {
		try {
			return type.getConstructor(String.class, Throwable.class).newInstance(message, causedBy);
		} catch (Exception e) {
			throw runtimeException(e);
		}
	}
}