src/jsr311-api/src/javax/ws/rs/core/EntityTag.java

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/*
 * EntityTag.java
 *
 * Created on March 21, 2007, 3:14 PM
 *
 */

package javax.ws.rs.core;

import javax.ws.rs.ext.RuntimeDelegate;
import javax.ws.rs.ext.RuntimeDelegate.HeaderDelegate;

/**
 * An abstraction for the value of a HTTP Entity Tag, used as the value 
 * of an ETag response header.
 * @see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.11">HTTP/1.1 section 3.11</a>
 */
public class EntityTag {
    
    private String value;
    private boolean weak;
    
    private static final HeaderDelegate<EntityTag> delegate = 
            RuntimeDelegate.getInstance().createHeaderDelegate(EntityTag.class);

    /**
     * Creates a new instance of a strong EntityTag. 
     * @param value the value of the tag, quotes not included. 
     * @throws IllegalArgumentException if value is null
     */
    public EntityTag(String value) {
        this(value, false);
    }
    
    /**
     * Creates a new instance of an EntityTag
     * @param value the value of the tag, quotes not included.
     * @param weak true if this represents a weak tag, false otherwise
     * @throws IllegalArgumentException if value is null
     */
    public EntityTag(String value, boolean weak) {
        if (value == null)
            throw new IllegalArgumentException("value==null");
        this.value = value;
        this.weak = weak;
    }
    
    /**
     * Creates a new instance of EntityTag by parsing the supplied string.
     * @param value the entity tag string
     * @return the newly created EntityTag
     * @throws IllegalArgumentException if the supplied string cannot be parsed
     * or is null
     */
    public static EntityTag valueOf(String value) throws IllegalArgumentException {
        return delegate.fromString(value);
    }
    
    /**
     * Check the strength of an EntityTag
     * @return true if this represents a weak tag, false otherwise
     */
    public boolean isWeak() {
        return weak;
    }
    
    /**
     * Get the value of an EntityTag
     * @return the value of the tag
     */
    public String getValue() {
        return value;
    }
    
    /**
     * Compares obj to this tag to see if they are the same considering weakness and
     * value.
     * @param obj the object to compare to
     * @return true if the two tags are the same, false otherwise.
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == null)
            return false;
        if (!(obj instanceof EntityTag))
            return super.equals(obj);
        EntityTag other = (EntityTag)obj;
        if (value.equals(other.getValue()) && weak==other.isWeak())
            return true;
        return false;
    }

    /**
     * Generate hashCode based on value and weakness.
     * @return the hashCode
     */
    @Override
    public int hashCode() {
        int hash = 3;
        hash = 17 * hash + (this.value != null ? this.value.hashCode() : 0);
        hash = 17 * hash + (this.weak ? 1 : 0);
        return hash;
    }

    /**
     * Convert the entity tag to a string suitable for use as the value of the
     * corresponding HTTP header.
     * @return a stringified entity tag
     */
    @Override
    public String toString() {
        return delegate.toString(this);
    }
}