juneau-core/juneau-marshall/src/main/java/org/apache/juneau/http/header/EntityTag.java

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package org.apache.juneau.http.header;

import static org.apache.juneau.internal.StringUtils.*;
import static org.apache.juneau.assertions.Assertions.*;
import static org.apache.juneau.internal.ExceptionUtils.*;
import static org.apache.juneau.internal.ObjectUtils.*;

/**
 * Represents a validator value.
 *
 * <p>
 * <h5 class='figure'>Example</h5>
 * <p class='bcode w800'>
 * 	ETag: "123456789"    – A strong ETag validator
 * 	ETag: W/"123456789"  – A weak ETag validator
 * </p>
 *
 * <ul class='seealso'>
 * 	<li class='extlink'>{@doc ExtRFC2616}
 * </ul>
 */
public class EntityTag {

	private final String value;
	private final boolean isWeak, isAny;

	/**
	 * Creator.
	 *
	 * @param value The validator string value.
	 * @return A new header bean or <jk>null</jk> if the value was <jk>null</jk>.
	 * @throws IllegalArgumentException If attempting to set an invalid entity tag value.
	 */
	public static EntityTag of(Object value) {
		Object o = unwrap(value);
		return (o == null ? null : new EntityTag(o.toString()));
	}

	/**
	 * Constructor.
	 *
	 * @param value The validator string value.
	 * @throws IllegalArgumentException If attempting to set an invalid entity tag value.
	 */
	public EntityTag(String value) {
		assertArgNotNull("value", value);

		value = trim(emptyIfNull(value));
		isWeak = value.startsWith("W/");
		isAny = "*".equals(value);

		if (! isAny) {
			if (isWeak)
				value = value.substring(2);
			if (value.length() > 1 && value.charAt(0) == '"' && value.charAt(value.length()-1) == '"')
				value = value.substring(1, value.length()-1);
			else
				throw illegalArgumentException("Invalid value for entity-tag: [{0}]", isWeak ? ("W/"+value) : value);
		}
		this.value = value;

	}

	/**
	 * Returns the validator value stripped of quotes and weak tag.
	 *
	 * @return The validator value.
	 */
	public String getEntityValue() {
		return value;
	}

	/**
	 * Returns <jk>true</jk> if the weak flag is present in the value.
	 *
	 * @return <jk>true</jk> if the weak flag is present in the value.
	 */
	public boolean isWeak() {
		return isWeak;
	}

	/**
	 * Returns <jk>true</jk> if the validator string value is <c>*</c>.
	 *
	 * @return <jk>true</jk> if the validator string value is <c>*</c>.
	 */
	public boolean isAny() {
		return isAny;
	}

	@Override
	public String toString() {
		return (isWeak ? "W/" : "") + (isAny() ? "*" : ('"' + value + '"'));
	}
}