RequestFactoryServlet意外错误 - 无法将Boolean转换为String

Question

我正在尝试将我的应用程序切换到java-7但是当我使用RequestFactory从appengine加载我的对象时，我收到以下错误：

com.google.web.bindery.requestfactory.server.RequestFactoryServlet doPost: Unexpected error
java.lang.ClassCastException: Cannot cast java.lang.Boolean to java.lang.String
    at java.lang.Class.cast(Class.java:3062)
    at com.google.web.bindery.autobean.vm.impl.BeanPropertyContext.set(BeanPropertyContext.java:44)
    at com.google.web.bindery.requestfactory.server.Resolver$PropertyResolver.visitValueProperty(Resolver.java:155)
    at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:289)
    at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166)
    at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101)
    at com.google.web.bindery.requestfactory.server.Resolver.resolveClientValue(Resolver.java:414)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.processInvocationMessages(SimpleRequestProcessor.java:491)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:233)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:135)
    at com.google.web.bindery.requestfactory.server.RequestFactoryServlet.doPost(RequestFactoryServlet.java:133)

使用java-6一切正常。这种情况只发生在java-7上，只发生在appengine上。当我使用带开发模式的java-7时没有问题。可能导致此问题的任何想法？