JPA+mysql+servlet实现的连接操作数据库的小例子

persistence.xml:

<?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="mysql" transaction-type="RESOURCE_LOCAL"><provider>org.hibernate.ejb.HibernatePersistence</provider>    <jta-data-source>java:comp/env/jdbc/mysql</jta-data-source>    <class>com.chinasoft.database2.Persion</class>   <properties><property name="hibernate.show_sql" value="true"></property>  </properties></persistence-unit>  </persistence>

?tomcat中server.xml配置：

  <Context path="/DatabaseTest" docBase="/DatabaseTest"  reloadable="false" crossContext="true"> <Resource name="jdbc/mysql"   auth="Container"  type="javax.sql.DataSource"  maxActive="5"   maxIdle="2"   maxWait="10000"   removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost/lpm?user=root&password=" />  </Context>

?建一个实体Persion类：

package com.chinasoft.database2;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="persion")public class Persion {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private java.lang.Long userid;    private java.lang.String name;      public java.lang.Long getUserid() {return userid;}public void setUserid(java.lang.Long userid) {this.userid = userid;}public java.lang.String getName() {return name;}public void setName(java.lang.String name) {this.name = name;}}

?建一个servlet类：

public class Start extends HttpServlet {?public void doGet(HttpServletRequest request, HttpServletResponse response)???throws ServletException, IOException {

?? EntityManagerFactory entityfactory = null;?? EntityTransaction? t=null;?? EntityManager em=null;??try{???entityfactory = Persistence.createEntityManagerFactory("mysql");???em=entityfactory.createEntityManager();??????Query query=em.createQuery("from Persion");???List list=query.getResultList();???Iterator iter=list.iterator();???while(iter.hasNext()){????Persion persion=(Persion) iter.next();????System.out.println(persion.getName());???}??????????? t=em.getTransaction();???t.begin();???Persion p=new Persion();???p.setName("abc");???em.persist(p);???t.commit();??}catch(Exception e){???e.printStackTrace();???t.rollback();??}??em.close();??entityfactory.close();?}}

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