src/exceptions/JavaException.java

package com.googlecode.prolog_cafe.exceptions;

import com.googlecode.prolog_cafe.lang.IntegerTerm;
import com.googlecode.prolog_cafe.lang.JavaObjectTerm;
import com.googlecode.prolog_cafe.lang.Operation;
import com.googlecode.prolog_cafe.lang.StructureTerm;
import com.googlecode.prolog_cafe.lang.SymbolTerm;
import com.googlecode.prolog_cafe.lang.Term;

/**
 * Java error.<br>
 * There will be a Java error when 
 * a Java exception is threw during interoperating with Java in Prolog Cafe.
 * The class <code>JavaException</code> wraps a subclass of <code>java.lang.Exception</code>.
 *
 * @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
 * @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
 * @version 1.0
 */
public class JavaException extends BuiltinException {
    private static final long serialVersionUID = 1L;

    /** A functor symbol of <code>java_error/3</code>. */
    public static final SymbolTerm JAVA_ERROR = SymbolTerm.intern("java_error", 3);

    /** Holds a Java exception. */
    public Exception e;

    /** Constructs a new <code>JavaException</code> with a Java exception. */
    public JavaException(Exception _e) {
	e = _e;
    }

    /** Constructs a new <code>JavaException</code> with the given arguments. */
    public JavaException(Operation _goal, int _argNo, Exception _e) {
	this.goal    = _goal;
	this.argNo   = _argNo;
	e = _e;
    }

    /** Returns a term representation of this <code>JavaException</code>:
     * <code>java_error(goal,argNo,exception)</code>.
     */
    @Override
    public Term getMessageTerm() {
	Term[] args = {
	    new JavaObjectTerm(goal), 
	    new IntegerTerm(argNo), 
	    new JavaObjectTerm(e)};
	return new StructureTerm(JAVA_ERROR, args);
    }

    /** Returns a underlying Java exception. */
    public Exception getException() {
	return e;
    }

    /** Returns a string representation of this <code>JavaException</code>. */
    @Override
    public String toString() {
	String s = "{JAVA ERROR: " + goal.toString();
	if (argNo > 0)
	    s += " - arg " + argNo;
	s += ", occurs " + e.toString();
	s += "}";
	return s;
    }
}