hibernate 连接问题
TOMCAT服务器运行几天后，网页就会有有java.lang.null异常，并且都显示不了数据，但是数据库里有数据。重新启动TOMCAT后又回复正常，我上网找是因为连接诶释放的问题，我的项目是用struts2+hibernate3.0 没用到SPRING，我也不知道哪错了，一直纠结了好多天。DAO层的代码贴在下面，麻烦大神们看看package com.dc_system.dao;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.hibernate.Hibernate;
import org.hibernate.Query;
import org.hibernate.SQLQuery;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.transform.Transformers;
import com.dc_system.hibernate.HibernateSessionFactory;
import com.dc_system.vo.DcUserVO;
public class BaseDAO<T> {
private Session session;
private Transaction trans;
public Session getSession() {
if(session == null)
session = HibernateSessionFactory.getSession();
return session;
}
public Transaction getTrans() {
if(trans == null)
trans = getSession().beginTransaction();
return trans;
}
public void closeSession(){
HibernateSessionFactory.closeSession();
}
public List getResBySQL(String sql,Class[] beanClass,Class targetClass) {
List list = new ArrayList();
try {
System.out.println(sql);
//getTrans().begin();
SQLQuery query = getSession().createSQLQuery(sql);
for(int i = 0 ;i < beanClass.length;i++)
query.addEntity(beanClass[i]);
if(beanClass.length > 1)
list = converVO(query.list(),targetClass);
else
list = query.list();
// getTrans().commit();
} catch (Exception e) {
e.printStackTrace();
//getTrans().rollback();
} finally {
trans = null;
closeSession();
}
return list;
}
/***
* 将得到后的结果转到目的的类
* @param list
* @param beanClass 转换成目标类
* @return
*/
public List converVO(List list,Class beanClass){
List list1 = new ArrayList();
Iterator iterator1 = list.iterator();
try {
while (iterator1.hasNext()) {
Object vo = beanClass.newInstance();
Object[] o = (Object[]) iterator1.next();
for(int i = 0 ;i < o.length;i++)
copyProperties(o[i], vo);
list1.add(vo);
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list1;
}
/***
* 多表查询返回一个VO
* @param hql
* @return
*/
public List getResByHQL(String hql,Class beanClass) {
List list = new ArrayList();
List list1 = new ArrayList();
try {
Query query = getSession().createQuery(hql);
list = query.list();
list1 = converVO(list,beanClass);
//getTrans().commit();
} catch (Exception e) {
e.printStackTrace();
//getTrans().rollback();
} finally {
trans = null;
closeSession();
}
return list1;
}
public List findByProperty(String property_name, Object value , String table_name,Class targetClass) {
try {
//getTrans().begin();
String queryString = "select * from "+table_name.toLowerCase()+" as model where model."
+ property_name + "='"+String.valueOf(value).toLowerCase()+"' and (model.del is null or model.del = 0)" ;
SQLQuery query = getSession().createSQLQuery(queryString);
query.addEntity(targetClass);
System.out.println(queryString);
return query.list();
} catch (Exception re) {
re.printStackTrace();
}finally {
trans = null;
closeSession();
}
return null;
}
/***
* 保存和更新
* @param transientInstance
*/
public void save(T transientInstance) {
try {
getTrans().begin();
getSession().saveOrUpdate(transientInstance);
getTrans().commit();
} catch (RuntimeException re) {
re.printStackTrace();
throw re;
}finally {
trans = null;
closeSession();
}
}
public void delete(T persistentInstance) {
try {
// getTrans().begin();
getSession().delete(persistentInstance);
getTrans().commit();
} catch (RuntimeException re) {
throw re;
}finally {
trans = null;
closeSession();
}
}
/***
* 获得所有的没有删除的数据
* @param table_name
* @param haveDel
* @param tableClass
* @return
*/
public List getAll(String table_name , Boolean haveDel,Class tableClass) {
try {
//getTrans().begin();
String sql="";
if(haveDel){
sql = "select * from "+table_name+" where del < 1 or del is null";
}else
sql = "select * from "+table_name;
return getResBySQL(sql, new Class[]{tableClass},tableClass);
} catch (RuntimeException re) {
throw re;
}finally {
trans = null;
closeSession();
}
}
public List getPageList(String table_name, String primerKey,int pageNo ,Boolean haveDel,Class tableClass){
try {
//getTrans().begin();
String sql="";
if(haveDel){
sql = "select * from "+table_name+" where (del < 1 or del is null) order by "+primerKey+" desc limit "
+ (pageNo-1)*10+",10 ";
}
return getResBySQL(sql, new Class[]{tableClass},tableClass);
} catch (RuntimeException re) {
throw re;
}finally {
trans = null;
closeSession();
}
}
/***
* 一个类复制到另一个类
* @param oldObj
* @param newObj
* @throws Exception
*/
public static void copyProperties(Object oldObj , Object newObj) throws Exception{
Class c1 = oldObj.getClass();
Class c2 = newObj.getClass();
//Field[] fields = c1.getDeclaredFields();
Method[] methods = c1.getMethods();
for(Method f : methods) {
if(f.getName().indexOf("set") == 0){
PropertyDescriptor pd1 = new PropertyDescriptor(f.getName().substring(3), c1);
Method getter = pd1.getReadMethod();
Object val = getter.invoke(oldObj);
try{
PropertyDescriptor pd2 = new PropertyDescriptor(f.getName().substring(3), c2);
Method setter = pd2.getWriteMethod();
setter.invoke(newObj, val);
}catch(Exception e){
System.out.println("-----------"+f.getName() +" is not found in "+newObj+"------------");
}
}
}
return;
}
public void upadateByHql(String hql){
try{
getTrans().begin();
Query query = getSession().createQuery(hql);
query.executeUpdate();
getTrans().commit();
}catch(Exception e){
e.printStackTrace();
}finally {
trans = null;
closeSession();
}
}
/**
* 获得记录数
* @return
*/
public Integer getCount(String tableName,String whereHQL,Class targetClass){
String hql="select count(*) as count from "+tableName +" "+ whereHQL;
SQLQuery query = getSession().createSQLQuery(hql.toLowerCase());
query.addScalar("count",Hibernate.INTEGER);
return (Integer) query.uniqueResult();
}
}
--------------------编程问答-------------------- 看下你hibernate的配置文件 --------------------编程问答--------------------
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools. -->
<hibernate-configuration>
<session-factory>
<property name="dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="connection.url">jdbc:mysql://localhost:3306/lyc_dc_server</property>
<property name="connection.username">lyc</property>
<property name="connection.password">uLW4PMHv5wZyu2aE</property>
<property name="connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="myeclipse.connection.profile">MYSQL</property>
<property name="c3p0.min_size">5</property>
<property name="c3p0.max_size">30</property>
<property name="c3p0.time_out">1800</property>
<property name="c3p0.max_statement">50</property>
<mapping resource="com/dc_system/bo/DcComment.hbm.xml" />
<mapping resource="com/dc_system/bo/DcArticle.hbm.xml" />
<mapping resource="com/dc_system/bo/DcUserDetail.hbm.xml" />
<mapping resource="com/dc_system/bo/DcUser.hbm.xml" />
<mapping resource="com/dc_system/bo/DcTea.hbm.xml" />
<mapping resource="com/dc_system/bo/DcAchievement.hbm.xml" />
<mapping resource="com/dc_system/bo/DcCommon.hbm.xml" />
<mapping resource="com/dc_system/bo/DcArea.hbm.xml" />
<mapping resource="com/dc_system/bo/DcVote.hbm.xml" />
<mapping resource="com/dc_system/bo/DcTrade.hbm.xml" />
</session-factory>
</hibernate-configuration> --------------------编程问答-------------------- <property name="c3p0.max_size">30</property> 这个弄大点 --------------------编程问答-------------------- 我按照网上说的添加CP30的数据库连接池，就这样在XML里添加这个代码啊？在DAO层还需要专门写一个获取连接的类吗？如果要添加JAVA代码的话，还要添加什么？ --------------------编程问答--------------------
调成300可以么？ --------------------编程问答-------------------- 嗯，再跑断时间看下 --------------------编程问答--------------------
原来我的项目没用到连接池，后来添加的，我就添加了一个CP30的JAR包，然后在hibernate这个配置文件添加这一段，其他什么都没做，这样可以吗？ --------------------编程问答-------------------- 嗯，，，跑下看看 --------------------编程问答-------------------- 如果mysql连接8小时内不操作的话，会被自己回收掉。。去加大Mysql连接超时时间吧 --------------------编程问答-------------------- 除 --------------------编程问答--------------------
当初第一个上线项目就是这mysql8小时问题，加大时间后就可以了，楼主可以试试
补充：Java , Web 开发
