mybatis连接数据库

第一次学习使用mybatis,花了好几个小时解决了各种问题，主要是配置方面的问题，但是最后总算实现了数据库读表。

1、现在的绝大多数web应用，通常都以action、service、dao三层去组织代码，这样划分结构很清晰，分工明确

2、一般情况下，我们会把事务控制在service层。

3、action和dao层，会使用一些框架技术。比如action层可能选择有springmvc、struts等，dao层有hibernate、mybatis等选择，所以action的dao有可能遂根据情况变化，而service层关注业务逻辑，业务代码都是自己完成的，代码对自己是透明的。

整个项目分为 dao层，Model层，service层，xml文件，以及mybatis-config.xml文件。

dao层：

package user.dao;import java.util.List;import user.model.User;public interface userDAO {public List<User> query2();public void insertPredict(User u); }

model层：

package user.model;public class User {private Integer userid;private Integer sex;private Integer userlvcd;public Integer getUserid() {return userid;}public void setUserid(Integer userid) {this.userid = userid;}public Integer getSex() {return sex;}public void setSex(Integer sex) {this.sex = sex;}public Integer getUserlvcd() {return userlvcd;}public void setUserlvcd(Integer userlvcd) {this.userlvcd = userlvcd;}}

service层：

IBuySevice.java

package user.service;import java.util.List;import user.model.User;public interface IBuyService extends ITransactionService{public List<User> predict();}

ITransactionService.java;

package user.service;import org.apache.ibatis.session.SqlSession;/** * 带事务的server，配合TransactionProxyManager，TransactionInvaocationHandler使用 * */public interface ITransactionService {public void setSession(SqlSession session);public SqlSession getSession();}

TransactionInvocationHandler:

package user.service;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;/** * 事务调用handler * @author shenan4321 * */public class TransactionInvocationHandler implements InvocationHandler {    private ITransactionService proxy;      private SqlSessionFactory factory;              /**     * 构造函数     * @param object     * @param factory     */    TransactionInvocationHandler(ITransactionService object, SqlSessionFactory factory)      {          this.proxy = object;          this.factory = factory;      }                  @Override    public Object invoke(Object o, Method method, Object[] objects) throws Throwable      {      SqlSession session = factory.openSession();          Object result = null;          try          {          proxy.setSession(session);                    result = method.invoke(proxy, objects);                          session.commit();          } catch (Exception e)          {          e.printStackTrace();        session.rollback();          } finally          {          session.close();          proxy.setSession(null);        }          return result;      }  }

TransactionProxyManager:

package user.service;import java.io.Reader;import java.lang.reflect.Proxy;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;/** * 事物代理管理器 * */public class TransactionProxyManager {protected static SqlSessionFactory sqlSessionFactory;protected static Reader reader;    static {        try {            reader = Resources.getResourceAsReader("mybatis-config.xml");            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);        } catch (Exception e) {            e.printStackTrace();        }    }    /**     * 开启session     * @return     */    public static SqlSession openSession() {        return sqlSessionFactory.openSession();    }    /**     * 关闭session     * @param session     */    public static void closeSession(SqlSession session){    session.close();    }         /**     * 为服务层代理事务     * @param object     * @return     */    public static Object proxyFor(ITransactionService object)    {      ClassLoader classLoder = object.getClass().getClassLoader();    @SuppressWarnings("rawtypes")Class[] interfaces = object.getClass().getInterfaces();        return Proxy.newProxyInstance(classLoder, interfaces, new TransactionInvocationHandler(object, sqlSessionFactory));      } }

UserServiceImpl:

package user.service;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.apache.ibatis.session.SqlSession;import user.dao.userDAO;import user.model.User;public class UserServiceImpl implements IBuyService{private SqlSession session;@Overridepublic SqlSession getSession() {return session;}@Overridepublic void setSession(SqlSession session) {this.session = session;}public List<User> predict(){List<User>  UserResult= getSession().getMapper(userDAO.class).query2();Map<Integer,Integer> userMap= new HashMap<Integer,Integer>();System.out.println("4月份(4/1~4/15)加购且下单的数量："+UserResult.size());Integer userId,sex,userlvcd;for(User u : UserResult){userId= u.getUserid();sex= u.getSex();userlvcd=u.getUserlvcd();System.out.println(userId+" "+sex+" "+userlvcd);}return UserResult;}public static void main(String[] args){IBuyService serv= (IBuyService) TransactionProxyManager.proxyFor(new UserServiceImpl());List<User> user1= serv.predict();}}

xml文件（userMapper.xml）：

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="user.dao.userDAO"><resultMap  type="User" id="UserResult"><result property="sex" column="sex" /><result property="userid" column="user_id" /><result property="userlvcd" column="user_lv_cd" /></resultMap>         <select id="query2" resultMap="UserResult" resultType="User">//resultMap=id的值         SELECT user_id,sex,user_lv_cd         FROM Jdata_user         WHERE user_id &it; 20         </select></mapper>

mybatis-config.xml:

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration><!--JD数据库配置--><typeAliases>          <typeAlias type="user.model.User" alias="User" />//alias的值要与上面的resulttype值相同        </typeAliases>      <environments default="development">        <environment id="development">        <transactionManager type="JDBC"/><dataSource type="POOLED">            <property name="driver" value="com.mysql.jdbc.Driver"/>                 <property name="url" value="jdbc:mysql://localhost:3306/mysql?useUnicode=true&characterEncoding=utf-8&useSSL=true"/>//易错            <property name="username" value="root"/>            <property name="password" value="1234"/>            </dataSource>        </environment>    </environments>      <!-- mybatis的mapper文件，每个xml配置文件对应一个接口 -->    <mappers>        <mapper resource="user/xml/userMapper.xml"/>    </mappers>      </configuration>

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