com.google.gwt.core.client.JavaScriptException.java Source code

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Here is the source code for com.google.gwt.core.client.JavaScriptException.java

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/*
 * Copyright 2008 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.core.client;

import com.google.gwt.core.client.impl.StackTraceCreator;

/**
 * Any JavaScript exceptions occurring within JSNI methods are wrapped as this
 * class when caught in Java code. The wrapping does not occur until the
 * exception passes out of JSNI into Java. Before that, the thrown object
 * remains a native JavaScript exception object, and can be caught in JSNI as
 * normal.
 * <p>
 * The return value of {@link #getStackTrace()} may vary between browsers due to
 * variations in the underlying error-reporting capabilities. When possible, the
 * stack trace will be the stack trace of the underlying error object. If it is
 * not possible to accurately report a stack trace, a zero-length array will be
 * returned. In those cases where the underlying stack trace cannot be
 * determined, {@link #fillInStackTrace()} can be called in the associated catch
 * block to create a stack trace corresponding to the location where the
 * JavaScriptException object was created.
 * 
 * <pre>
 * try {
 *   nativeMethod();
 * } catch (JavaScriptException e) {
 *   if (e.getStackTrace().length == 0) {
 *     e.fillInStackTrace();
 *   }
 * }
 * </pre>
 */
public final class JavaScriptException extends RuntimeException {

    private static String getDescription(Object e) {
        if (e instanceof JavaScriptObject) {
            return getDescription0((JavaScriptObject) e);
        } else {
            return e + "";
        }
    }

    private static native String getDescription0(JavaScriptObject e) /*-{
                                                                     return (e == null) ? null : e.message;
                                                                     }-*/;

    private static String getName(Object e) {
        if (e == null) {
            return "null";
        } else if (e instanceof JavaScriptObject) {
            return getName0((JavaScriptObject) e);
        } else if (e instanceof String) {
            return "String";
        } else {
            return e.getClass().getName();
        }
    }

    private static native String getName0(JavaScriptObject e) /*-{
                                                              return (e == null) ? null : e.name;
                                                              }-*/;

    private static String getProperties(Object e) {
        return (GWT.isScript() && e instanceof JavaScriptObject)
                ? StackTraceCreator.getProperties((JavaScriptObject) e)
                : "";
    }

    /**
     * The original description of the JavaScript exception this class wraps,
     * initialized as <code>e.message</code>.
     */
    private String description;

    /**
     * The underlying exception this class wraps.
     */
    private final Object e;

    /**
     * A constructed message describing this exception.
     */
    private String message;

    /**
     * The original type name of the JavaScript exception this class wraps,
     * initialized as <code>e.name</code>.
     */
    private String name;

    /**
     * @param e the object caught in JavaScript that triggered the exception
     */
    public JavaScriptException(Object e) {
        this.e = e;
        /*
         * In Development Mode, JavaScriptExceptions are created exactly when the
         * native method returns and their stack traces are fixed-up by the
         * hosted-mode plumbing.
         *
         * In Production Mode, we'll attempt to infer the stack trace from the
         * thrown object, although this is not possible in all browsers.
         */
        if (GWT.isScript()) {
            StackTraceCreator.createStackTrace(this);
        }
    }

    public JavaScriptException(String name, String description) {
        this.message = "JavaScript " + name + " exception: " + description;
        this.name = name;
        this.description = description;
        this.e = null;
    }

    /**
     * Used for server-side instantiation during JUnit runs. Exceptions are
     * manually marshaled through
     * <code>com.google.gwt.junit.client.impl.ExceptionWrapper</code> objects.
     * 
     * @param message the detail message
     */
    protected JavaScriptException(String message) {
        super(message);
        this.message = this.description = message;
        this.e = null;
    }

    /**
     * Returns the original JavaScript message of the exception; may be
     * <code>null</code>.
     */
    public String getDescription() {
        if (message == null) {
            init();
        }
        return description;
    }

    /**
     * Returns the original JavaScript the exception; may be <code>null</code>.
     */
    public JavaScriptObject getException() {
        return (e instanceof JavaScriptObject) ? (JavaScriptObject) e : null;
    }

    @Override
    public String getMessage() {
        if (message == null) {
            init();
        }
        return message;
    }

    /**
     * Returns the original JavaScript type name of the exception; may be
     * <code>null</code>.
     */
    public String getName() {
        if (message == null) {
            init();
        }
        return name;
    }

    private void init() {
        name = getName(e);
        description = getDescription(e);
        message = "(" + name + "): " + description + getProperties(e);
    }

}