/*
* Copyright 2012 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.shared;
/**
* Supports core functionality that in some cases requires direct support from
* the compiler and runtime systems such as runtime type information and
* deferred binding.
*/
public final class GWT {
/**
* Always <code>null</code> in Production Mode; in Development Mode provides
* the implementation for certain methods.
*/
private static GWTBridge sGWTBridge = null;
/**
* Instantiates a class via deferred binding.
*
* <p>
* The argument to {@link #create(Class)} <i>must</i> be a class literal
* because the Production Mode compiler must be able to statically determine
* the requested type at compile-time. This can be tricky because using a
* {@link Class} variable may appear to work correctly in Development Mode.
* </p>
*
* @param classLiteral a class literal specifying the base class to be
* instantiated
* @return the new instance, which must be cast to the requested class
*/
public static <T> T create(Class<?> classLiteral) {
if (sGWTBridge == null) {
/*
* In Production Mode, the compiler directly replaces calls to this method
* with a new Object() type expression of the correct rebound type.
*/
throw new UnsupportedOperationException(
"ERROR: GWT.create() is only usable in client code! It cannot be called, "
+ "for example, from server code. If you are running a unit test, "
+ "check that your test case extends GWTTestCase and that GWT.create() "
+ "is not called from within an initializer or constructor.");
} else {
return sGWTBridge.<T> create(classLiteral);
}
}
/**
* Returns the empty string when running in Production Mode, but returns a
* unique string for each thread in Development Mode (for example, different
* windows accessing the dev mode server will each have a unique id, and
* hitting refresh without restarting dev mode will result in a new unique id
* for a particular window.
*
* TODO(unnurg): Remove this function once Dev Mode rewriting classes are in
* gwt-dev.
*/
public static String getUniqueThreadId() {
if (sGWTBridge != null) {
return sGWTBridge.getThreadUniqueID();
}
return "";
}
/**
* Get a human-readable representation of the GWT version used, or null if
* this is running on the client.
*
* @return a human-readable version number, such as {@code "2.5"}
*/
public static String getVersion() {
return sGWTBridge == null ? null : sGWTBridge.getVersion();
}
/**
* Returns <code>true</code> when running inside the normal GWT environment,
* either in Development Mode or Production Mode. Returns <code>false</code>
* if this code is running in a plain JVM. This might happen when running
* shared code on the server, or during the bootstrap sequence of a
* GWTTestCase test.
*/
public static boolean isClient() {
// Replaced with "true" by GWT compiler.
return sGWTBridge != null && sGWTBridge.isClient();
}
/**
* Returns <code>true</code> when running in production mode. Returns
* <code>false</code> when running either in development mode, or when running
* in a plain JVM.
*/
public static boolean isProdMode() {
// Replaced with "true" by GWT compiler.
return false;
}
/**
* Determines whether or not the running program is script or bytecode.
*/
public static boolean isScript() {
// Replaced with "true" by GWT compiler.
return false;
}
/**
* Logs a message to the development shell logger in Development Mode. Calls
* are optimized out in Production Mode.
*/
public static void log(String message) {
log(message, null);
}
/**
* Logs a message to the development shell logger in Development Mode. Calls
* are optimized out in Production Mode.
*/
public static void log(String message, Throwable e) {
if (sGWTBridge != null) {
sGWTBridge.log(message, e);
}
}
/**
* Called via reflection in Development Mode; do not ever call this method in
* Production Mode. May be called in server code to initialize server bridge.
*/
public static void setBridge(GWTBridge bridge) {
sGWTBridge = bridge;
}
}