com.google.gwt.useragent.client.UserAgentAsserter Maven / Gradle / Ivy
/*
* Copyright 2011 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.useragent.client;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
/**
* Helper class, which, during startup, asserts that the specified user.agent
* selection property value indeed matches the expected value for this browser /
* user agent, thus avoid long hours debugging strange error messages when a
* single user agent compile, typically created for testing purposes, ends up
* being executed in the wrong browser.
*/
public class UserAgentAsserter implements EntryPoint {
/**
* Interface to provide both the compile time and runtime
* user.agent selection property value.
*/
interface UserAgentProperty {
String getCompileTimeValue();
String getRuntimeValue();
boolean getUserAgentRuntimeWarning();
}
/**
* Default {@link UserAgentProperty} implementation used when
* {@code user.agent.runtimeWarning} is {@code false}.
*/
static class UserAgentPropertyDisabled implements UserAgentProperty {
@Override
public String getCompileTimeValue() {
return null;
}
@Override
public String getRuntimeValue() {
return null;
}
@Override
public boolean getUserAgentRuntimeWarning() {
return false;
}
}
@Override
public void onModuleLoad() {
UserAgentProperty impl = GWT.create(UserAgentProperty.class);
if (!impl.getUserAgentRuntimeWarning()) {
return;
}
String compileTimeValue = impl.getCompileTimeValue();
String runtimeValue = impl.getRuntimeValue();
if (!compileTimeValue.equals(runtimeValue)) {
displayMismatchWarning(runtimeValue, compileTimeValue);
}
}
/**
* Implemented as a JSNI method to avoid potentially using any user agent
* specific deferred binding code, since this method is called precisely when
* we're somehow executing code from the wrong user.agent permutation.
*/
private native void displayMismatchWarning(String runtimeValue,
String compileTimeValue) /*-{
$wnd.alert("ERROR: Possible problem with your *.gwt.xml module file."
+ "\nThe compile time user.agent value (" + compileTimeValue
+ ") does not match the runtime user.agent value (" + runtimeValue
+ "). Expect more errors.\n");
}-*/;
}