restAPI中提供的demo有时候运行没有问题，有时候又会抛异常，代码都没动

抛出的异常是什么？ 贴出来看看
 

直接运行demo main方法中的实例 在获取token时候 返回的，tokenResponse对象为HTTP/1.0 302 Moved Temporarily [Location: http://10.16.248.2/auth_entry.php?authmeth=3&webtype=0&orgi=http://a1.easemob.com, Content-Type: text/html;, Content-Length: 0]，token为null
异常就是空指针异常
java.lang.RuntimeException: java.lang.NullPointerException
 at com.easemob.server.example.httpclient.utils.HTTPClientUtils.sendHTTPRequest(HTTPClientUtils.java:123)
 at com.easemob.server.example.httpclient.apidemo.EasemobIMUsers.createNewIMUserSingle(EasemobIMUsers.java:179)
 at com.easemob.server.example.httpclient.apidemo.EasemobIMUsers.main(EasemobIMUsers.java:45)
Caused by: java.lang.NullPointerException
 at com.easemob.server.example.httpclient.vo.Token.applyAuthentication(Token.java:29)
 at com.easemob.server.example.httpclient.vo.Token.applyAuthentication(Token.java:25)
 at com.easemob.server.example.httpclient.utils.HTTPClientUtils.sendHTTPRequest(HTTPClientUtils.java:78)
 ... 2 more
 
我把demo中的代码拷贝到我的工程，接收前台的注册信息时候，也是
    HttpResponse tokenResponse = client.execute(httpPost);
    HttpEntity entity = tokenResponse.getEntity();
这两句代码直接就抛异常 ，tokenResponse 对象都没接受到 。
异常如下：
java.lang.RuntimeException: java.lang.RuntimeException: Some errors occurred while fetching a token by username and password .
 at iaf.im.httpclient.utils.HTTPClientUtils.sendHTTPRequest(HTTPClientUtils.java:123)
 at iaf.im.web.UserController.createNewIMUserSingle(UserController.java:152)
 at iaf.im.web.UserController.register(UserController.java:52)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:601)
 at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
 at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
 at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
 at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
 at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
 at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
 at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:957)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
 at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
 at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
 at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
 at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.RuntimeException: Some errors occurred while fetching a token by username and password .
 at iaf.im.httpclient.vo.ClientSecretCredential.getToken(ClientSecretCredential.java:103)
 at iaf.im.httpclient.vo.Token.applyAuthentication(Token.java:25)
 at iaf.im.httpclient.utils.HTTPClientUtils.sendHTTPRequest(HTTPClientUtils.java:78)
 ... 39 more
 
 
最最关键的是前天这些代码就报这些错，而 昨天这些代码运行的好好的，今天一开机，运行，又挂了 ！！！