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Java example source code file (NashornException.java)

This example Java source code file (NashornException.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, engine_script_source_name, list, nashornexception, runtimeexception, stacktraceelement, string, stringbuilder, suppresswarnings, throwable, util

The NashornException.java Java example source code

/*
 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.api.scripting;

import java.util.ArrayList;
import java.util.List;
import jdk.nashorn.internal.codegen.CompilerConstants;
import jdk.nashorn.internal.runtime.ECMAErrors;

/**
 * This is base exception for all Nashorn exceptions. These originate from
 * user's ECMAScript code. Example: script parse errors, exceptions thrown from
 * scripts. Note that ScriptEngine methods like "eval", "invokeMethod",
 * "invokeFunction" will wrap this as ScriptException and throw it. But, there
 * are cases where user may need to access this exception (or implementation
 * defined subtype of this). For example, if java interface is implemented by a
 * script object or Java access to script object properties via java.util.Map
 * interface. In these cases, user code will get an instance of this or
 * implementation defined subclass.
 */
@SuppressWarnings("serial")
public abstract class NashornException extends RuntimeException {
    // script file name
    private final String fileName;
    // script line number
    private final int line;
    // script column number
    private final int column;

    /** script source name used for "engine.js" */
    public static final String ENGINE_SCRIPT_SOURCE_NAME = "nashorn:engine/resources/engine.js";

    /**
     * Constructor
     *
     * @param msg       exception message
     * @param fileName  file name
     * @param line      line number
     * @param column    column number
     */
    protected NashornException(final String msg, final String fileName, final int line, final int column) {
        this(msg, null, fileName, line, column);
    }

    /**
     * Constructor
     *
     * @param msg       exception message
     * @param cause     exception cause
     * @param fileName  file name
     * @param line      line number
     * @param column    column number
     */
    protected NashornException(final String msg, final Throwable cause, final String fileName, final int line, final int column) {
        super(msg, cause == null ? null : cause);
        this.fileName = fileName;
        this.line = line;
        this.column = column;
    }

    /**
     * Constructor
     *
     * @param msg       exception message
     * @param cause     exception cause
     */
    protected NashornException(final String msg, final Throwable cause) {
        super(msg, cause == null ? null : cause);
        // This is not so pretty - but it gets the job done. Note that the stack
        // trace has been already filled by "fillInStackTrace" call from
        // Throwable
        // constructor and so we don't pay additional cost for it.

        // Hard luck - no column number info
        this.column = -1;

        // Find the first JavaScript frame by walking and set file, line from it
        // Usually, we should be able to find it in just few frames depth.
        for (final StackTraceElement ste : getStackTrace()) {
            if (ECMAErrors.isScriptFrame(ste)) {
                // Whatever here is compiled from JavaScript code
                this.fileName = ste.getFileName();
                this.line = ste.getLineNumber();
                return;
            }
        }

        this.fileName = null;
        this.line = 0;
    }

    /**
     * Get the source file name for this {@code NashornException}
     *
     * @return the file name
     */
    public final String getFileName() {
        return fileName;
    }

    /**
     * Get the line number for this {@code NashornException}
     *
     * @return the line number
     */
    public final int getLineNumber() {
        return line;
    }

    /**
     * Get the column for this {@code NashornException}
     *
     * @return the column
     */
    public final int getColumnNumber() {
        return column;
    }

    /**
     * Returns array javascript stack frames from the given exception object.
     *
     * @param exception exception from which stack frames are retrieved and filtered
     * @return array of javascript stack frames
     */
    public static StackTraceElement[] getScriptFrames(final Throwable exception) {
        final StackTraceElement[] frames = exception.getStackTrace();
        final List<StackTraceElement> filtered = new ArrayList<>();
        for (final StackTraceElement st : frames) {
            if (ECMAErrors.isScriptFrame(st)) {
                final String className = "<" + st.getFileName() + ">";
                String methodName = st.getMethodName();
                if (methodName.equals(CompilerConstants.RUN_SCRIPT.symbolName())) {
                    methodName = "<program>";
                }
                filtered.add(new StackTraceElement(className, methodName,
                        st.getFileName(), st.getLineNumber()));
            }
        }
        return filtered.toArray(new StackTraceElement[filtered.size()]);
    }

    /**
     * Return a formatted script stack trace string with frames information separated by '\n'
     *
     * @param exception exception for which script stack string is returned
     * @return formatted stack trace string
     */
    public static String getScriptStackString(final Throwable exception) {
        final StringBuilder buf = new StringBuilder();
        final StackTraceElement[] frames = getScriptFrames(exception);
        for (final StackTraceElement st : frames) {
            buf.append("\tat ");
            buf.append(st.getMethodName());
            buf.append(" (");
            buf.append(st.getFileName());
            buf.append(':');
            buf.append(st.getLineNumber());
            buf.append(")\n");
        }
        final int len = buf.length();
        // remove trailing '\n'
        if (len > 0) {
            assert buf.charAt(len - 1) == '\n';
            buf.deleteCharAt(len - 1);
        }
        return buf.toString();
    }
}

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