requestToken = function() {
    var getTokenURI = '/gettoken?userid=' + userid;
    var httpRequest = makeRequest(getTokenURI, true);

    httpRequest.onreadystatechange = function() {
        if (httpRequest.readyState == 4) {
            if (httpRequest.status == 200) {
                openChannel(httpRequest.responseText);
            } else {
                alert('ERROR: AJAX request status = ' + httpRequest.status);
            }
        }
    }
};

function makeRequest(url, async) {
    var httpRequest;
    if (window.XMLHttpRequest) {

        httpRequest = new XMLHttpRequest();

    } else if (window.ActiveXObject) {
        // IE
        try {

            httpRequest = new ActiveXObject("Msxml2.XMLHTTP");

        } catch (e) {
            try {

                httpRequest = new ActiveXObject("Microsoft.XMLHTTP");

            } catch (e) {
            }
        }
    }

    if (!httpRequest) {

        return false;
    }

    httpRequest.open('POST', url, async);
    httpRequest.send();

    return httpRequest;
}

它在localhost上运行非常好…但是在Google App
Engine上，它的httpRequest.status等于500，并进入else语句。为什么？

在Google App Engine上登录：

/getFriendList?userid=d 500 253ms 0kb Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11
175.110.179.86 - - [17/Dec/2012:08:35:33 -0800] "POST /getFriendList?userid=d HTTP/1.1" 500 0 "http://faisalimmsngr.appspot.com/" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11" "faisalimmsngr.appspot.com" ms=254 cpu_ms=110 instance=00c61b117caf2d11ca57d2a2296ccd0b902b038a
W 2012-12-17 08:35:33.272
Failed startup of context com.google.apphosting.utils.jetty.RuntimeAppEngineWebAppContext@10ff62a{/,/base/data/home/apps/s~faisalimmsngr/1.363934467542140431}
org.mortbay.util.MultiException[java.lang.UnsupportedClassVersionError: adv/web/mid/exam/FriendServlet : Unsupported major.minor version 51.0, java.lang.UnsupportedClassVersionError: adv/web/mid/exam/MessageServlet : Unsupported major.minor version 51.0, java.lang.UnsupportedClassVersionError: adv/web/mid/exam/TokenServlet : Unsupported major.minor version 51.0]
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:656)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:219)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:194)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:134)
    at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:447)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:454)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:461)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:703)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:338)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:330)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:458)
    at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
    at java.lang.Thread.run(Thread.java:679)
java.lang.UnsupportedClassVersionError: adv/web/mid/exam/FriendServlet : Unsupported major.minor version 51.0
    at com.google.appengine.runtime.Request.process-c04431eac3a1f275(Request.java)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
    at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at org.mortbay.util.Loader.loadClass(Loader.java:91)
    at org.mortbay.util.Loader.loadClass(Loader.java:71)
    at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:73)
    at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:454)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:461)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:703)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:338)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:330)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:458)
    at java.lang.Thread.run(Thread.java:679)