ExceptionAnalyzer.java

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package com.sun.enterprise.admin.cli.remote;

import java.util.ArrayList;
import java.util.List;

/** An immutable class to analyze the exception stack trace of a given
 * instance of {@link java.lang.Exception}. Can be extended to handle
 * throwables, but it is not done in this version on purpose. Takes the
 * snapshot of given exception at the time of instantiation.
 * @author केदार (km@dev.java.net)
 * @since GlassFish v3 Prelude
 */

final class ExceptionAnalyzer {
    
    private final Exception exc;
    private final List<Throwable> chain;
    ExceptionAnalyzer(Exception e) {
        if (e == null)
            throw new IllegalArgumentException("null arg");
        this.exc   = e;
        this.chain = new ArrayList<Throwable>();
        chain.add(exc);
        build();
    }
    
    private void build() {
        Throwable t = exc.getCause();
        while (t != null) {
            chain.add(t);
            t = t.getCause();
        }
    }
    
    /** Returns the first instance of the given Exception class in the chain
     *  of causes. The counting starts from the instance of the Exception that
     *  created the ExceptionAnalyzer class itself.
     * @param ac the unknown subclass of Exception that needs the chain to be examined for
     * @return first instance of given Throwable (returned object will be an
     * instance of the given class) or null if there is no such instance
     */ 
    Throwable getFirstInstanceOf(Class<? extends Exception> ac) {
        for (Throwable t : chain) {
            try {
                ac.cast(t);
                return t;
            } catch(ClassCastException cce) {
                //ignore and continue
            }
        }
        return null;
    }
}