com.fasterxml.jackson.databind.type.ClassKey Maven / Gradle / Ivy

package com.fasterxml.jackson.databind.type;

/**
 * Key class, used as an efficient and accurate key
 * for locating per-class values, such as
 * {@link com.fasterxml.jackson.databind.JsonSerializer}s.
 *
 * The reason for having a separate key class instead of
 * directly using {@link Class} as key is mostly
 * to allow for redefining hashCode method --
 * for some strange reason, {@link Class} does not
 * redefine {@link Object#hashCode} and thus uses identity
 * hash, which is pretty slow. This makes key access using
 * {@link Class} unnecessarily slow.
 *
 * Note: since class is not strictly immutable, caller must
 * know what it is doing, if changing field values.
 */
public final class ClassKey
    implements Comparable,
        java.io.Serializable // since 2.1
{
    private static final long serialVersionUID = 1L;

    private String _className;

    private Class _class;

    /**
     * Let's cache hash code straight away, since we are
     * almost certain to need it.
     */
    private int _hashCode;

    public ClassKey() 
    {
        _class = null;
        _className = null;
        _hashCode = 0;
    }

    public ClassKey(Class clz)
    {
        _class = clz;
        _className = clz.getName();
        _hashCode = _className.hashCode();
    }

    public void reset(Class clz)
    {
        _class = clz;
        _className = clz.getName();
        _hashCode = _className.hashCode();
    }

    /*
    /**********************************************************
    /* Comparable
    /**********************************************************
     */

    @Override
    public int compareTo(ClassKey other)
    {
        // Just need to sort by name, ok to collide (unless used in TreeMap/Set!)
        return _className.compareTo(other._className);
    }

    /*
    /**********************************************************
    /* Standard methods
    /**********************************************************
     */

    @Override
        public boolean equals(Object o)
    {
        if (o == this) return true;
        if (o == null) return false;
        if (o.getClass() != getClass()) return false;
        ClassKey other = (ClassKey) o;

        /* Is it possible to have different Class object for same name + class loader combo?
         * Let's assume answer is no: if this is wrong, will need to uncomment following functionality
         */
        /*
        return (other._className.equals(_className))
            && (other._class.getClassLoader() == _class.getClassLoader());
        */
        return other._class == _class;
    }

    @Override public int hashCode() { return _hashCode; }

    @Override public String toString() { return _className; }
    
}