hibernate 关联查询报错解决方法

//查询的hql            StringBuffer hql = new StringBuffer("select d,p from DriverInfo d,Parameter p where d.licenseType = p.id.paramKey And p.id.paramType = ? ");            //存入字段            ArrayList<Object> param = new ArrayList<Object>();            param.add("licenseType");            if(name!=null && !name.equals("")){                hql.append(" And d.name = ?");                param.add(name);            }            if(driverLicense!=null && !driverLicense.equals("")){                hql.append(" And d.driverLicense = ?");                param.add(driverLicense);            }                        List<Object> drivers = (List<Object>) this.queryForPage(hql.toString(),param, offset, length);                        List<DriverInfo> drs = null ;                        for(int i=0 ;i<drivers.size();i++){                Object[] ob =(Object[]) drivers.get(i);                System.out.println(ob[0]);                DriverInfo driver =(DriverInfo) ob[0]; //报错行                Parameter parame = (Parameter) ob[1];                driver.setLicenseType(parame.getParamValue());                drs.add(driver);            }            return drs;

public List<?> queryForPage(final String hql,final ArrayList<Object> param,final int offset, final int length)    {        List<?> list = getHibernateTemplate().executeFind(new HibernateCallback()        {            public Object doInHibernate(Session session) throws HibernateException, SQLException            {                Query query = session.createQuery(hql);                //插入查询条件                if(param.size()>0){                    for(int i=0;i<param.size();i++){                        query.setParameter(i, param.get(i));                    }                }                //设置分页                query.setFirstResult(offset);                query.setMaxResults(length);                List<?> list = query.list();                return list;            }        });        return list;    }

2011-10-12 00:16:01,932 DEBUG [http-8080-3] (SQLStatementLogger.java:111) - select driverinfo0_.DRIVER_ID as DRIVER1_7_0_, parameter1_.PARAM_TYPE as PARAM1_11_1_, parameter1_.PARAM_KEY as PARAM2_11_1_, driverinfo0_.NAME as NAME7_0_, driverinfo0_.PHONE as PHONE7_0_, driverinfo0_.DRIVER_LICENSE as DRIVER4_7_0_, driverinfo0_.LICENSE_TYPE as LICENSE5_7_0_, driverinfo0_.LICENSE_YEAR as LICENSE6_7_0_, driverinfo0_.NOTE as NOTE7_0_, parameter1_.PARAM_VALUE as PARAM3_11_1_, parameter1_.PARAM_DESC as PARAM4_11_1_ from transport.tb_driver_info driverinfo0_, transport.tb_parameter parameter1_ where driverinfo0_.LICENSE_TYPE=parameter1_.PARAM_KEY and parameter1_.PARAM_TYPE=? limit ?java.lang.NullPointerException    at lxt.action.DriverAction.loadAll(DriverAction.java:54)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)    at java.lang.reflect.Method.invoke(Unknown Source)    at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:441)    at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:280)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:243)    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:165)    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:252)    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:130)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:165)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:179)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485)    at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at lxt.action.core.LoginFilter.doFilter(LoginFilter.java:37)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)    at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)    at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)    at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)    at java.lang.Thread.run(Unknown Source)