10001---MyBatis介绍

MyBatis是支持普通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.

编写第一个基于mybaits的测试例子:

添加jar包

  mybatis-3.1.1.jar
  mysql-connector-java-5.1.7-bin.jar

建库+表

  create database mybatis;
  use mybatis;
  CREATE TABLE users(id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20), age INT);
  INSERT INTO users(NAME, age) VALUES('Tom', 12);
  INSERT INTO users(NAME, age) VALUES('Jack', 11);

添加Mybatis的配置文件conf.xml(在src文件下)

<?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><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/mybatis" /><property name="username" value="root" /><property name="password" value="root" /></dataSource></environment></environments></configuration>

定义表所对应的实体类

public class User {private int id;private String name;private int age;    //get,set方法}

定义操作users表的sql映射文件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="com.mybatis.userMapper"> <select id="selectUser" parameterType="int" resultType="com.mybatis.User">select * from users where id=#{id}</select></mapper>

在conf.xml文件中注册userMapper.xml文件

<mappers><mapper resource="com/mybatis/userMapper.xml"/></mappers>

编写测试代码：执行定义的select语句

public class Test {public static void main(String[] args) throws IOException {String resource = "conf.xml"; //加载mybatis的配置文件（它也加载关联的映射文件）Reader reader = Resources.getResourceAsReader(resource); //构建sqlSession的工厂SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);//创建能执行映射文件中sql的sqlSessionSqlSession session = sessionFactory.openSession();//映射sql的标识字符串String statement = "com.mybatis.userMapper"+".selectUser";//执行查询返回一个唯一user对象的sqlUser user = session.selectOne(statement, 1);System.out.println(user);}}

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public static void main(String[] args) throws IOException {String resource = "conf.xml"; InputStream is = Test.class.getClassLoader().getResourceAsStream(resource);SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);SqlSession session = factory.openSession();String statement = "com.atguigu.day03_mybaits.test1.userMapper.getUser";User user = session.selectOne(statement, 2);System.out.println(user);}}