AXIS调用WEBSERVICE报错，求帮助。

服务端也报错了，异常信息如下：
五月 24, 2013 11:57:20 下午 com.sun.xml.internal.ws.server.sei.EndpointMethodHandler invoke
SEVERE: null
java.lang.NullPointerException
at cn.com.gdjtny.service.BigAntService.sendMsg(BigAntService.java:51)
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 com.sun.xml.internal.ws.api.server.InstanceResolver$1.invoke(InstanceResolver.java:235)
at com.sun.xml.internal.ws.server.InvokerTube$2.invoke(InvokerTube.java:135)
at com.sun.xml.internal.ws.server.sei.EndpointMethodHandler.invoke(EndpointMethodHandler.java:246)
at com.sun.xml.internal.ws.server.sei.SEIInvokerTube.processRequest(SEIInvokerTube.java:85)
at com.sun.xml.internal.ws.api.pipe.Fiber.__doRun(Fiber.java:626)
at com.sun.xml.internal.ws.api.pipe.Fiber._doRun(Fiber.java:585)
at com.sun.xml.internal.ws.api.pipe.Fiber.doRun(Fiber.java:570)
at com.sun.xml.internal.ws.api.pipe.Fiber.runSync(Fiber.java:467)
at com.sun.xml.internal.ws.server.WSEndpointImpl$2.process(WSEndpointImpl.java:299)
at com.sun.xml.internal.ws.transport.http.HttpAdapter$HttpToolkit.handle(HttpAdapter.java:593)
at com.sun.xml.internal.ws.transport.http.HttpAdapter.handle(HttpAdapter.java:244)
at com.sun.xml.internal.ws.transport.http.server.WSHttpHandler.handleExchange(WSHttpHandler.java:95)
at com.sun.xml.internal.ws.transport.http.server.WSHttpHandler.handle(WSHttpHandler.java:80)
at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:77)
at sun.net.httpserver.AuthFilter.doFilter(AuthFilter.java:83)
at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:80)
at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(ServerImpl.java:668)
at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:77)
at sun.net.httpserver.ServerImpl$Exchange.run(ServerImpl.java:640)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)