Mybatis

一.Mybatis介绍

     MyBatis是一个支持普通SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis消除了几乎所有的JDBC代码和参数的手工设置以及对结果集的检索封装。MyBatis可以使用简单的XML或注解用于配置和原始映射，将接口和Java的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录。

二.Mybatis jar包

   需要准备的引用包

　　mybatis-3.2.8.jar：myBatis框架使用

<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>3.2.2</version>
</dependency>

　　ojdbc6.jar：数据库连接

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-Java</artifactId>
  <version>5.1.36</version>
</dependency>

三.结构分析

　　1）需要配置文件连接数据库；

　　2）需要公共方法提供数据库连接的使用；

　　3）PO：持久对象

　　4）数据查询SQL配置XML文件；

　　5）对外接口；

四.结构搭建

示例如下：

 IStudentInfoDAO.java

package cn.happy.dao;

import cn.happy.entity.StudentInfo;

import java.util.List;

/**
 * Created by Happy on 2017-07-09.
 */
public interface IStudentInfoDAO {
     //01.查询所有的学生信息
    public List<StudentInfo> findAll();
    //02.根据学生学号查询特定学生对象
    public  StudentInfo getStudentById(int stuid);
}

IStudentInfoDAO.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!--头文件-->
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <!--namespace：
     命名空间：区分不同空间下的同名SQLID
     A： findlAll
     B:  findAll
    -->
<mapper namespace="cn.happy.dao.IStudentInfoDAO">
    <!--SQL标签
      id:唯一锁定到SQL标识
      paramenterType:SQL语句的入参  可以省略
      resultType：
      增删除操作：不能 写
      查询：单个实体的类型
    -->
    <select id="findAll" resultType="StudentInfo">
        /*SQL文：SQL语句*/
        select * from studentinfo
    </select>
    <!--按主键查询-->
    <select id="getStudentById" resultType="StudentInfo">
        select * from studentinfo WHERE stuid=#{stuId}
    </select>
</mapper>

StudentInfo.java

package cn.happy.entity;

import java.util.Date;

/**
 * Created by Happy on 2017-07-09.
 */
public class StudentInfo {
     private Integer stuId;
     private String stuName;
     private Integer  stuAge;
     private Date stuDate;

    public Integer getStuId() {
        return stuId;
    }

    public void setStuId(Integer stuId) {
        this.stuId = stuId;
    }

    public String getStuName() {
        return stuName;
    }

    public void setStuName(String stuName) {
        this.stuName = stuName;
    }

    public Integer getStuAge() {
        return stuAge;
    }

    public void setStuAge(Integer stuAge) {
        this.stuAge = stuAge;
    }

    public Date getStuDate() {
        return stuDate;
    }

    public void setStuDate(Date stuDate) {
        this.stuDate = stuDate;
    }
}

MyBatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!--文档类型，头文件-->
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--根节点，XMl只能有一个-->
<configuration>
    <typeAliases>
        <!--<typeAlias type="cn.happy.entity.StudentInfo" alias="StudentInfo"></typeAlias>-->
        <!--将该包中的简单类型 StudentInfo作为类的别名-->
        <package name="cn.happy.entity"></package>
    </typeAliases>
    <!--一个environments有N个environment-->
    <environments default="development">
        <environment id="development">
            <!--
            transactionManager:JDBC保证事务的
            update
            delete
            事务分类：JDBC:编程式事务
                        xxx.beginTransaction()

                        tx.commit()
                        tx.rollback()
                      配置式事务
                      JDBC|MANAGED
                      区别
            -->
            <transactionManager type="JDBC"/>
            <!--
                POOLED：MyBatis内置的连接池
                c3p0连接池
                        POOLED 、UNPOOLED  、JNDI
            -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/y2165"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>

    </environments>

    <mappers>
        <mapper resource="cn/happy/dao/IStudentInfoDAO.xml"/>
    </mappers>
</configuration>

MyBatisTest0709.java

package cn.happy.test;

import cn.happy.dao.IStudentInfoDAO;
import cn.happy.entity.StudentInfo;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * Created by Happy on 2017-07-09.
 */
public class MyBatisTest0709 {

    @Test
    //03.根据主键查询单个对象  getMapper（）方式
    public void testSelectOneByGetMapper(){
        String path="MyBatis-config.xml";
        InputStream is= null;
        try {
            is = Resources.getResourceAsStream(path);
            SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(is);
            SqlSession session=factory.openSession();
            IStudentInfoDAO dao = session.getMapper(IStudentInfoDAO.class);
            StudentInfo info = dao.getStudentById(3);
            System.out.println(info.getStuName());
            /*MyBatisTest0709 my=new MyBatisTest0709();
            Class<MyBatisTest0709> clazz = (Class<MyBatisTest0709>) my.getClass();
            try {
                Class<MyBatisTest0709> clazzz = (Class<MyBatisTest0709>)Class.forName("cn.happy.test.MyBatisTest0709");
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }*/
            session.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    @Test
    //02.根据主键查询单个对象
    public void testSelectOne(){
        String path="MyBatis-config.xml";
        InputStream is= null;
        try {
            is = Resources.getResourceAsStream(path);
            SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(is);
            SqlSession session=factory.openSession();
            StudentInfo info = session.selectOne("getStudentById",3);
            System.out.println(info.getStuName());

            session.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

     @Test
    public void testAll(){
         String path="MyBatis-config.xml";
         InputStream is= null;
         try {
             is = Resources.getResourceAsStream(path);
             SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(is);
             SqlSession session=factory.openSession();
             List<StudentInfo> list = session.selectList("findAll");
             for (StudentInfo info:list) {
                 System.out.println(info.getStuName());
             }
             session.close();
         } catch (IOException e) {
             e.printStackTrace();
         }

     }
}