org.hibernate.impl.SessionImpl.get(SessionImpl)
代码
package com.me.common.dao.impl;
import java.io.Serializable;
import java.util.List;
import java.util.Map;
import org.hibernate.Query;
import org.hibernate.Session;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
import com.me.common.dao.BaseDao;
import com.me.util.ToolsUtil;
import com.me.vo.PageVo;
public class BaseDaoImpl<T> extends HibernateDaoSupport implements BaseDao<T> {
private Class<T> clazz;
/*
* 添加对象
*/
@Override
public boolean insert(T entity) {
Session session = this.getSession();
session.save(entity);
return true;
}
/*
* 更新对象
*/
@Override
public boolean update(T entity) {
Session session = this.getSession();
session.update(entity);
return true;
}
/*
* 根据Id查找
*/
@SuppressWarnings("unchecked")
@Override
public T queryById(Serializable id) {
Session session = this.getSession();
T object = (T)session.get(clazz, id);
return object;
}
/*
*无条件查找
*/
@SuppressWarnings("unchecked")
@Override
public List<T> queryByPage(PageVo pageVo) {
Session session = this.getSession();
Query query = session.createQuery("from " + clazz.getName());
List<T> objects = query.setFirstResult((pageVo.getPageNo()-1)*pageVo.getPageCount()).setMaxResults(pageVo.getPageSize()).list();
return objects;
}
/**
* 条件交集查找
* @param condition
* @param pageVo
* @return
*/
@SuppressWarnings("unchecked")
@Override
public List<T> queryByConditionIntersection (Map<String, Object> condition, PageVo pageVo) {
if(condition.isEmpty())
return queryByPage(pageVo);
else{
Session session = this.getSession();
Query query = session.createQuery("from "+clazz.getName()+ ToolsUtil.convertConditionIntersection(condition));
List<T> objects = (List<T>) query.setFirstResult((pageVo.getPageNo()-1)*pageVo.getPageCount()).setMaxResults(pageVo.getPageCount());
return objects;
}
}
/**
* 条件并集查找
* @param condition
* @param pageVo
* @return
*/
@SuppressWarnings("unchecked")
@Override
public List<T> queryByConditionUnion(Map<String, Object> condition, PageVo pageVo) {
if(condition.isEmpty())
return queryByPage(pageVo);
else{
Session session = this.getSession();
Query query = session.createQuery("from "+clazz.getName()+ ToolsUtil.convertConditionUnion(condition));
List<T> objects = (List<T>) query.setFirstResult((pageVo.getPageNo()-1)*pageVo.getPageCount()).setMaxResults(pageVo.getPageCount());
return objects;
}
}
}
所有的数据库操作类都将继承该BaseDao
错误：
java.lang.NullPointerException at org.hibernate.impl.SessionImpl.get(SessionImpl.java:990) at com.me.common.dao.impl.BaseDaoImpl.queryById(BaseDaoImpl.java:51) at com.me.service.impl.UserServiceImpl.queryUserById(UserServiceImpl.java:32) at com.me.controller.UserController.queryUser(UserController.java:25) 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 org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:746) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:687) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:811) at javax.servlet.http.HttpServlet.service(HttpServlet.java:620) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796) at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) 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:107) 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:503) 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:950) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source)
解决方案：
我所遇到的这个问题，是因为我不了解反射。
没有加：
/**
* 通过反射泛型获取Class类型,getGenericSuperclass()方法获取对象的泛型的父类类型信息，
* getActualTypeArguments()[0]方法得到T的真实类型
*
*/
@SuppressWarnings("unchecked")
public BaseDaoImpl() {
ParameterizedType pt = (ParameterizedType) this.getClass()
.getGenericSuperclass();
this.clazz = (Class<T>) pt.getActualTypeArguments()[0];
}
现在正在认真理解中......