JPA连接数据库

<?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0"> <persistence-unit name="PHMSPU" transaction-type="RESOURCE_LOCAL"> <provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider> <class>cn.wiztek.phm.domain.Assets</class> <class>cn.wiztek.phm.domain.Rentalreport</class> <class>cn.wiztek.phm.domain.Rentinfo</class> <!-- .......... --> <!-- <class>cn.wiztek.phm.domain.Menu2</class>--> <properties> <property name="openjpa.ConnectionURL" value="jdbc:db2://192.168.50.211:50000/PHMS" /> <property name="openjpa.ConnectionDriverName" value="com.ibm.db2.jcc.DB2Driver" /> <property name="openjpa.ConnectionUserName" value="db2inst1" /> <property name="openjpa.ConnectionPassword" value="wiztek" /> <property name="openjpa.Log" value="log4j" /> </properties> </persistence-unit> </persistence>

 

其中 <class>cn.wiztek.phm.domain.Assets</class>为与数据库表对应的Bean路径；

<properties/> 为 数据库的连接信息；

然后，创建类

package cn.wiztek.phm.util; import java.util.logging.Level; import java.util.logging.Logger; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; import javax.persistence.Query; public class EntityManagerHelper { private static final EntityManagerFactory emf; private static final ThreadLocal<EntityManager> threadLocal; private static final Logger logger; static { emf = Persistence.createEntityManagerFactory("PHMSPU"); //该处名称与上面配置文件一致 threadLocal = new ThreadLocal<EntityManager>(); logger = Logger.getLogger("PHMSPU"); logger.setLevel(Level.ALL); } public static EntityManager getEntityManager() { EntityManager manager = threadLocal.get(); if (manager == null || !manager.isOpen()) { logger.info("getting EntityManager"); manager = emf.createEntityManager(); System.out.println(manager); threadLocal.set(manager); } return manager; } public static void closeEntityManager() { EntityManager em = threadLocal.get(); threadLocal.set(null); if (em != null && em.isOpen()) { logger.info("closing EntityManager"); em.close(); } } public static void beginTransaction() { logger.info("begining Transaction"); getEntityManager().getTransaction().begin(); } public static void commit() { logger.info("commiting transaction"); getEntityManager().getTransaction().commit(); } public static void rollback() { logger.info("rollback transaction"); getEntityManager().getTransaction().rollback(); } public static Query createQuery(String query) { return getEntityManager().createQuery(query); } public static void log(String info, Level level, Throwable ex) { logger.log(level, info, ex); } }

 

 

数据库操作：

package cn.wiztek.phm.dao.impl; import java.util.List; import java.util.logging.Level; import javax.persistence.EntityManager; import javax.persistence.Query; import cn.wiztek.phm.dao.CommonDao; import cn.wiztek.phm.util.EntityManagerHelper; public class CommonDaoImpl implements CommonDao { private EntityManager getEntityManager(){ return EntityManagerHelper.getEntityManager(); } /** * 添加对象操作 * @param <T> * @param entityClass * @param t * @return */ public<T> boolean addObject(Class<?> entityClass,T t){ EntityManagerHelper.log("addObject "+entityClass.getSimpleName(),Level.INFO,null); try{ getEntityManager().persist(t); getEntityManager().flush(); EntityManagerHelper.log("addObject success",Level.INFO,null); return true; }catch(Exception e){ EntityManagerHelper.log("addObject failed",Level.SEVERE,e); return false; } } /** * 更新对象操作 * @param <T> * @param entityClass * @param t * @return */ public<T> boolean modiObject(Class<T> entityClass,T t){ EntityManagerHelper.log("modiObject "+entityClass.getSimpleName(),Level.INFO,null); try{ getEntityManager().merge(t); EntityManagerHelper.log("modiObject success",Level.INFO,null); return true; }catch(Exception e){ EntityManagerHelper.log("modiObject failed",Level.SEVERE,e); return false; } } /** * 执行sql操作，主要用于更新和删除 * @param sql * @return */ public boolean execSql(String sql){ EntityManagerHelper.log("execSql sql is : "+sql,Level.INFO,null); int num; try{ Query query = getEntityManager().createQuery(sql); num = query.executeUpdate(); }catch(Exception e){ EntityManagerHelper.log("execSql failed : ",Level.SEVERE,e); return false; } if(num == 0){ EntityManagerHelper.log("execSql num is 0 ",Level.INFO,null); } return true; } /** * 根据sql进行查询操作 * @param sql * @param firse 开始行 * @param size 步长 * @return */ @SuppressWarnings("unchecked") public List queryObject(final String sql,final int first,final int size ){ EntityManagerHelper.log("queryObject sql is : "+sql,Level.INFO,null); try{ List rlist; Query query = getEntityManager().createQuery(sql); int nfirst = first < 0 ? 0 : first; query.setFirstResult(nfirst); if(size >0){ query.setMaxResults(size); } rlist = query.getResultList(); return rlist; }catch(Exception e){ EntityManagerHelper.log("queryObject failed : "+sql,Level.SEVERE,e); return null; } } /** * 查询条数 * @param sql * @return */ public Integer queryCount(final String sql){ EntityManagerHelper.log("queryCount sql is : "+sql,Level.INFO,null); try{ Query query = getEntityManager().createQuery(sql); return (Integer)query.getSingleResult(); }catch(Exception e){ EntityManagerHelper.log("queryCount failed : "+sql,Level.SEVERE,e); return 0; } } }