求高手看一看！index.jsp可以进，在往上点就出现有关问题了

求高手看一看！index.jsp可以进，在往下点就出现问题了！
HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
com.xdd.web.Login.execute(Login.java:36)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:453)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)
org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)