vaadin-framework/server/src/main/java/com/vaadin/server/DefaultErrorHandler.java

/*
 * Copyright 2000-2018 Vaadin Ltd.
 *
 * 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.vaadin.server;

import java.lang.reflect.InvocationTargetException;
import java.net.SocketException;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.vaadin.event.ListenerMethod.MethodException;
import com.vaadin.server.ClientConnector.ConnectorErrorEvent;
import com.vaadin.server.ServerRpcManager.RpcInvocationException;
import com.vaadin.shared.Connector;
import com.vaadin.ui.AbstractComponent;
import com.vaadin.ui.Component;

public class DefaultErrorHandler implements ErrorHandler {
    @Override
    public void error(ErrorEvent event) {
        doDefault(event);
    }

    public static void doDefault(ErrorEvent event) {
        Throwable t = event.getThrowable();
        if (t instanceof SocketException) {
            // Most likely client browser closed socket
            getLogger().info("SocketException in CommunicationManager."
                    + " Most likely client (browser) closed socket.");
            return;
        }

        t = findRelevantThrowable(t);

        // Finds the original source of the error/exception
        AbstractComponent component = findAbstractComponent(event);
        if (component != null) {
            // Shows the error in AbstractComponent
            ErrorMessage errorMessage = AbstractErrorMessage
                    .getErrorMessageForException(t);
            component.setComponentError(errorMessage);
        }

        // also print the error on console
        getLogger().log(Level.SEVERE, "", t);
    }

    /**
     * Vaadin wraps exceptions in its own and due to reflection usage there
     * might be also other irrelevant exceptions that make no sense for Vaadin
     * users (~developers using Vaadin). This method tries to choose the
     * relevant one to be reported.
     *
     * @since 7.2
     * @param t
     *            a throwable passed to ErrorHandler
     * @return the throwable that is relevant for Vaadin users
     */
    public static Throwable findRelevantThrowable(Throwable t) {
        try {
            if ((t instanceof RpcInvocationException)
                    && (t.getCause() instanceof InvocationTargetException)) {
                /*
                 * RpcInvocationException (that always wraps irrelevant
                 * java.lang.reflect.InvocationTargetException) might only be
                 * relevant for core Vaadin developers.
                 */
                return findRelevantThrowable(t.getCause().getCause());
            } else if (t instanceof MethodException) {
                /*
                 * Method exception might only be relevant for core Vaadin
                 * developers.
                 */
                return t.getCause();
            }
        } catch (Exception e) {
            // NOP, just return the original one
        }
        return t;
    }

    private static Logger getLogger() {
        return Logger.getLogger(DefaultErrorHandler.class.getName());
    }

    /**
     * Returns the AbstractComponent associated with the given error if such can
     * be found.
     *
     * @param event
     *            The error to investigate
     * @return The {@link AbstractComponent} to error relates to or null if
     *         could not be determined or if the error does not relate to any
     *         AbstractComponent.
     */
    public static AbstractComponent findAbstractComponent(
            com.vaadin.server.ErrorEvent event) {
        if (event instanceof ConnectorErrorEvent) {
            Component c = findComponent(
                    ((ConnectorErrorEvent) event).getConnector());
            if (c instanceof AbstractComponent) {
                return (AbstractComponent) c;
            }
        }

        return null;
    }

    /**
     * Finds the nearest component by traversing upwards in the hierarchy. If
     * connector is a Component, that Component is returned. Otherwise, looks
     * upwards in the hierarchy until it finds a {@link Component}.
     *
     * @return A Component or null if no component was found
     */
    public static Component findComponent(Connector connector) {
        if (connector instanceof Component) {
            return (Component) connector;
        }
        if (connector.getParent() != null) {
            return findComponent(connector.getParent());
        }

        return null;
    }

}