一、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。

二、快速入门

2.1 准备

首先需要添加两个jar包，一个是mybatis-3.1.1.jar，一个是mysql-connector-java-5.1.7-bin.jar。然后在MySQL中建立数据库和数据表：

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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);

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

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		select * from users where id=#{id}
	

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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sqlSession
		SqlSession session = sessionFactory.openSession();
		//映射sql的标识字符串
		String statement = "com.atguigu.mybatis.bean.userMapper"+".selectUser";
		//执行查询返回一个唯一user对象的sql
		User user = session.selectOne(statement, 1);
		System.out.println(user);

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3.1 XML的实现

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	insert into users(name, age) values(#{name}, #{age});



	delete from users where id=#{id}

		

	update users set name=#{name},age=#{age} where id=#{id}

		

	select * from users where id=#{id}

		

	select * from users

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public interface UserMapper {
	@Insert("insert into users(name, age) values(#{name}, #{age})")
	public int insertUser(User user);

	@Delete("delete from users where id=#{id}")
	public int deleteUserById(int id);
			
	@Update("update users set name=#{name},age=#{age} where id=#{id}")
	public int updateUser(User user);

	@Select("select * from users where id=#{id}")
	public User getUserById(int id);

	@Select("select * from users")
	public List getAllUser();
}

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public User getUserById(int id) {
	SqlSession session = sessionFactory.openSession();
	UserMapper mapper = session.getMapper(UserMapper.class);
	User user = mapper.getUserById(id);
	return user;
}

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4.1 建立数据库配置文件

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## db.properties

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4.3 添加log4j配置文件，打印日志信息

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#log4j.properties
log4j.rootLogger=DEBUG, Console
#Console
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n
log4j.logger.java.sql.ResultSet=INFO
log4j.logger.org.apache=INFO
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

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