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package com.sun.xml.xsom.parser;

import org.xml.sax.ContentHandler;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;

/**
 * Used to parse {@code <xs:annotation>}.
 * 
 * @author Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
 */
public abstract class AnnotationParser {
    /**
     * Called every time a new {@code <xs:annotation>} element
     * is found.
     * 
     * The sub-tree rooted at {@code <xs:annotation>} will be
     * sent to this ContentHandler as if it is a whole document.
     * 
     * @param context
     *      indicates the schema component that owns this annotation.
     *      Always non-null.
     * @param parentElementName
     *      local name of the element that contains {@code <xs:annotation>}.
     *      (e.g., "element", "attribute", ... )
     * @param errorHandler
     *      The error handler that the client application specifies.
     *      The returned content handler can send its errors to this
     *      object.
     * @param entityResolver
     *      The entity resolver that is currently in use. Again,
     *      The returned content handler can use this object
     *      if it needs to resolve entities.
     */
    public abstract ContentHandler getContentHandler(
        AnnotationContext context,
        String parentElementName,
        ErrorHandler errorHandler,
        EntityResolver entityResolver );
    
    /**
     * Once the SAX events are fed to the ContentHandler,
     * this method will be called to retrieve the parsed result.
     * 
     * @param existing
     *      An annotation object which was returned from another
     *      AnnotationParser before. Sometimes, one schema component
     *      can have multiple {@code <xs:annotation>} elements and
     *      this parameter is used to merge all those annotations
     *      together. If there is no existing object, null will be
     *      passed.
     * @return
     *      Any object, including null.
     */
    public abstract Object getResult( Object existing );
}