vaadin-framework/server/src/main/java/com/vaadin/ui/AbstractJavaScriptComponent.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.ui;

import com.vaadin.server.JavaScriptCallbackHelper;
import com.vaadin.server.JsonCodec;
import com.vaadin.shared.communication.ServerRpc;
import com.vaadin.shared.ui.JavaScriptComponentState;

import elemental.json.Json;
import elemental.json.JsonValue;

/**
 * Base class for Components with all client-side logic implemented using
 * JavaScript.
 * <p>
 * When a new JavaScript component is initialized in the browser, the framework
 * will look for a globally defined JavaScript function that will initialize the
 * component. The name of the initialization function is formed by replacing .
 * with _ in the name of the server-side class. If no such function is defined,
 * each super class is used in turn until a match is found. The framework will
 * thus first attempt with <code>com_example_MyComponent</code> for the
 * server-side
 * <code>com.example.MyComponent extends AbstractJavaScriptComponent</code>
 * class. If MyComponent instead extends <code>com.example.SuperComponent</code>
 * , then <code>com_example_SuperComponent</code> will also be attempted if
 * <code>com_example_MyComponent</code> has not been defined.
 * <p>
 * JavaScript components have a very simple GWT widget (
 * {@link com.vaadin.client.ui.JavaScriptWidget} ) just consisting of a single
 * element (a <code>div</code> by default) to which the JavaScript code should
 * initialize its own user interface. The tag can be overridden by defining a
 * string named <code>com_example_MyComponent.tag</code>. If no tag has been
 * defined, a tag defined in a super class will be located in the same manner as
 * with the init function.
 * <p>
 * For example, to create a component ({@code my.package.Span}) with the DOM
 * {@code <span>some text</span>}, taking the {@code span} text from the state,
 * the JavaScript would be:
 *
 * <pre>
 * <code>
my_package_Span = function() {
  this.onStateChange = function() {
    this.getElement().innerText = this.getState().text;
  }
}
my_package_Span.tag = "span";
</code>
 * </pre>
 *
 * <p>
 * The initialization function will be called with <code>this</code> pointing to
 * a connector wrapper object providing integration to Vaadin. Please note that
 * in JavaScript, <code>this</code> is not necessarily defined inside callback
 * functions and it might therefore be necessary to assign the reference to a
 * separate variable, e.g. <code>var self = this;</code>. The following
 * functions are provided by the connector wrapper object:
 * <ul>
 * <li><code>getConnectorId()</code> - returns a string with the id of the
 * connector.</li>
 * <li><code>getParentId([connectorId])</code> - returns a string with the id of
 * the connector's parent. If <code>connectorId</code> is provided, the id of
 * the parent of the corresponding connector with the passed id is returned
 * instead.</li>
 * <li><code>getElement([connectorId])</code> - returns the DOM Element that is
 * the root of a connector's widget. <code>null</code> is returned if the
 * connector can not be found or if the connector doesn't have a widget. If
 * <code>connectorId</code> is not provided, the connector id of the current
 * connector will be used.</li>
 * <li><code>getState()</code> - returns an object corresponding to the shared
 * state defined on the server. The scheme for conversion between Java and
 * JavaScript types is described bellow.</li>
 * <li><code>registerRpc([name, ] rpcObject)</code> - registers the
 * <code>rpcObject</code> as a RPC handler. <code>rpcObject</code> should be an
 * object with field containing functions for all eligible RPC functions. If
 * <code>name</code> is provided, the RPC handler will only used for RPC calls
 * for the RPC interface with the same fully qualified Java name. If no
 * <code>name</code> is provided, the RPC handler will be used for all incoming
 * RPC invocations where the RPC method name is defined as a function field in
 * the handler. The scheme for conversion between Java types in the RPC
 * interface definition and the JavaScript values passed as arguments to the
 * handler functions is described bellow.</li>
 * <li><code>getRpcProxy([name])</code> - returns an RPC proxy object. If
 * <code>name</code> is provided, the proxy object will contain functions for
 * all methods in the RPC interface with the same fully qualified name, provided
 * a RPC handler has been registered by the server-side code. If no
 * <code>name</code> is provided, the returned RPC proxy object will contain
 * functions for all methods in all RPC interfaces registered for the connector
 * on the server. If the same method name is present in multiple registered RPC
 * interfaces, the corresponding function in the RPC proxy object will throw an
 * exception when called. The scheme for conversion between Java types in the
 * RPC interface and the JavaScript values that should be passed to the
 * functions is described bellow.</li>
 * <li><code>translateVaadinUri(uri)</code> - Translates a Vaadin URI to a URL
 * that can be used in the browser. This is just way of accessing
 * {@link com.vaadin.client.ApplicationConnection#translateVaadinUri(String)}</li>
 * <li><code>addResizeListener(element, callbackFunction)</code> - Registers a
 * listener that gets notified whenever the size of the provided element
 * changes. The listener is called with one parameter: an event object with the
 * <code>element</code> property pointing to the element that has been resized.
 * <li><code>removeResizeListener(element, callbackFunction)</code> -
 * Unregisters a combination of an element and a listener that has previously
 * been registered using <code>addResizeListener</code>. All registered
 * listeners are automatically unregistered when this connector is unregistered,
 * but this method can be use to to unregister a listener at an earlier point in
 * time.
 * </ul>
 * The connector wrapper also supports these special functions:
 * <ul>
 * <li><code>onStateChange</code> - If the JavaScript code assigns a function to
 * the field, that function is called whenever the contents of the shared state
 * is changed.</li>
 * <li><code>onUnregister</code> - If the JavaScript code assigns a function to
 * the field, that function is called when the connector has been
 * unregistered.</li>
 * <li>Any field name corresponding to a call to
 * {@link #addFunction(String, JavaScriptFunction)} on the server will
 * automatically be present as a function that triggers the registered function
 * on the server.</li>
 * <li>Any field name referred to using {@link #callFunction(String, Object...)}
 * on the server will be called if a function has been assigned to the
 * field.</li>
 * </ul>
 * <p>
 *
 * Values in the Shared State and in RPC calls are converted between Java and
 * JavaScript using the following conventions:
 * <ul>
 * <li>Primitive Java numbers (byte, char, int, long, float, double) and their
 * boxed types (Byte, Character, Integer, Long, Float, Double) are represented
 * by JavaScript numbers.</li>
 * <li>The primitive Java boolean and the boxed Boolean are represented by
 * JavaScript booleans.</li>
 * <li>Java Strings are represented by JavaScript strings.</li>
 * <li>Java Dates are represented by JavaScript numbers containing the timestamp
 * </li>
 * <li>List, Set and all arrays in Java are represented by JavaScript
 * arrays.</li>
 * <li>Map&lt;String, ?&gt; in Java is represented by JavaScript object with
 * fields corresponding to the map keys.</li>
 * <li>Any other Java Map is represented by a JavaScript array containing two
 * arrays, the first contains the keys and the second contains the values in the
 * same order.</li>
 * <li>A Java Bean is represented by a JavaScript object with fields
 * corresponding to the bean's properties.</li>
 * <li>A Java Connector is represented by a JavaScript string containing the
 * connector's id.</li>
 * <li>A pluggable serialization mechanism is provided for types not described
 * here. Please refer to the documentation for specific types for serialization
 * information.</li>
 * </ul>
 *
 * @author Vaadin Ltd
 * @since 7.0.0
 */
public abstract class AbstractJavaScriptComponent extends AbstractComponent {
    private final JavaScriptCallbackHelper callbackHelper = new JavaScriptCallbackHelper(
            this);

    @Override
    protected <T extends ServerRpc> void registerRpc(T implementation,
            Class<T> rpcInterfaceType) {
        super.registerRpc(implementation, rpcInterfaceType);
        callbackHelper.registerRpc(rpcInterfaceType);
    }

    /**
     * Register a {@link JavaScriptFunction} that can be called from the
     * JavaScript using the provided name. A JavaScript function with the
     * provided name will be added to the connector wrapper object (initially
     * available as <code>this</code>). Calling that JavaScript function will
     * cause the call method in the registered {@link JavaScriptFunction} to be
     * invoked with the same arguments.
     *
     * @param functionName
     *            the name that should be used for client-side function
     * @param function
     *            the {@link JavaScriptFunction} object that will be invoked
     *            when the JavaScript function is called
     */
    protected void addFunction(String functionName,
            JavaScriptFunction function) {
        callbackHelper.registerCallback(functionName, function);
    }

    /**
     * Invoke a named function that the connector JavaScript has added to the
     * JavaScript connector wrapper object. The arguments can be any boxed
     * primitive type, String, {@link JsonValue} or arrays of any other
     * supported type. Complex types (e.g. List, Set, Map, Connector or any
     * JavaBean type) must be explicitly serialized to a {@link JsonValue}
     * before sending. This can be done either with
     * {@link JsonCodec#encode(Object, JsonValue, java.lang.reflect.Type, com.vaadin.ui.ConnectorTracker)}
     * or using the factory methods in {@link Json}.
     *
     * @param name
     *            the name of the function
     * @param arguments
     *            function arguments
     */
    protected void callFunction(String name, Object... arguments) {
        callbackHelper.invokeCallback(name, arguments);
    }

    @Override
    protected JavaScriptComponentState getState() {
        return (JavaScriptComponentState) super.getState();
    }

    @Override
    protected JavaScriptComponentState getState(boolean markAsDirty) {
        return (JavaScriptComponentState) super.getState(markAsDirty);
    }
}