Java MyBatis3（1）入门
MyBatis3介绍
mybatis就是一个封装来jdbc的持久层框架，它和hibernate都属于ORM框架，但是具体的说，hibernate是一个完全的orm框架，而mybatis是一个不完全的orm框架。
Mybatis让程序员只关注sql本身，而不需要去关注如连接的创建、statement的创建等操作。
Mybatis会将输入参数、输出结果进行映射。
MyBatis3原理
1、mybatis配置
SqlMapConfig.xml，此文件作为mybatis的全局配置文件，配置了mybatis的运行环境等信息。
mapper.xml文件即sql映射文件，文件中配置了操作数据库的sql语句。此文件需要在SqlMapConfig.xml中加载。
2、通过mybatis环境等配置信息构造SqlSessionFactory即会话工厂
3、由会话工厂创建sqlSession即会话，操作数据库需要通过sqlSession进行。
4、mybatis底层自定义了Executor执行器接口操作数据库，Executor接口有两个实现，一个是基本执行器、一个是缓存执行器。
5、Mapped Statement也是mybatis一个底层封装对象，它包装了mybatis配置信息及sql映射信息等。mapper.xml文件中一个sql对应一个Mapped Statement对象，sql的id即是Mapped statement的id。
6、Mapped Statement对sql执行输入参数进行定义，包括HashMap、基本类型、pojo，Executor通过Mapped Statement在执行sql前将输入的java对象映射至sql中，输入参数映射就是jdbc编程中对preparedStatement设置参数。
7、Mapped Statement对sql执行输出结果进行定义，包括HashMap、基本类型、pojo，Executor通过Mapped Statement在执行sql后将输出结果映射至java对象中，输出结果映射过程相当于jdbc编程中对结果的解析处理过程。
MyBatis3入门使用
1.mysql表结构
创建表语句
CREATE TABLE `user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `username` varchar(32) NOT NULL COMMENT '用户名称', `birthday` date DEFAULT NULL COMMENT '生日', `sex` char(1) DEFAULT NULL COMMENT '性别', `address` varchar(256) DEFAULT NULL COMMENT '地址', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=31 DEFAULT CHARSET=utf8
测试数据
insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('1','王五',NULL,'2',NULL); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('10','张三','2014-07-10','1','北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('16','张小明',NULL,'1','北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('22','陈小明',NULL,'1','北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('24','张三丰',NULL,'1','北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('25','陈小明',NULL,'1','北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('26','王五',NULL,NULL,'北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('27','小六子',NULL,NULL,'北京市'); insert into `user` (`id`, `username`, `birthday`, `sex`, `address`) values('35','沐风',NULL,NULL,'北京市');
2.搭建如下工程
3.Mybatis的核心包和依赖包
4. User.java类
package com.mf.mybatis.po;
import java.io.Serializable;
import java.util.Date;
@SuppressWarnings("serial")
public class User implements Serializable{
private int id;
private String username;
private String sex;
private Date birthday;
private String address;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", sex=" + sex
+ ", birthday=" + birthday + ", address=" + address + "]";
}
}
5.创建全局配置文件
<?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"></transactionManager> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8" /> <property name="username" value="root" /> <property name="password" value="root" /> </dataSource> </environment> </environments> <mappers> <mapper resource="User.xml" /> </mappers> </configuration>
6.在config目录下，创建User.xml（这种命名规范是由ibatis遗留下来）
<?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="test"> <select id="findUserById" parameterType="int" resultType="com.mf.mybatis.po.User"> SELECT * FROM USER WHERE id =#{id} </select> <insert id="insertUser" parameterType="com.mf.mybatis.po.User"> <selectKey keyProperty="id" resultType="int" order="AFTER"> SELECT LAST_INSERT_ID() </selectKey> INSERT INTO USER (username,birthday,sex,address) VALUES(#{username},#{birthday},#{sex},#{address}) </insert> </mapper>
7.测试代码
package com.mf.mybatis.first; import java.io.InputStream; import java.util.List; 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 com.mf.mybatis.po.User; public class MybatisFirst { @Test public void findUserByIdTest() throws Exception{ //读取配置文件 //全局配置文件的路径 String resource = "SqlMapConfig.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); //创建SqlSessionFactory SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //创建SqlSession SqlSession sqlSession = sqlSessionFactory.openSession(); //调用SqlSession的增删改查方法 //第一个参数：表示statement的唯一标示 User user = sqlSession.selectOne("test.findUserById", 1); System.out.println(user); //关闭资源 sqlSession.close(); } @Test public void insertUserTest() throws Exception{ String resource = "SqlMapConfig.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSession sqlSession = sqlSessionFactory.openSession(); User user = new User(); user.setUsername("沐风"); user.setAddress("mufeng"); sqlSession.insert("test.insertUser", user); System.out.println(user.getId()); sqlSession.commit(); sqlSession.close(); } }
