Mybatis学习01 - Mybatis入门案例及工作原理分析
环境搭建
1.在数据库中创建表user并添加数据
CREATE TABLE `users` (
`id` int(11) NOT NULL auto_increment,
`username` varchar(32) NOT NULL COMMENT '用户名称',
`birthday` datetime default NULL COMMENT '生日',
`sex` char(1) default NULL COMMENT '性别',
`address` varchar(256) default NULL COMMENT '地址',
PRIMARY KEY (`id`)
)
insert into `users`(`id`,`username`,`birthday`,`sex`,`address`) values (41,'老王','2018-02-27 17:47:08','男','北京'),(43,'小二王','2018-03-04 11:34:34','女','北京金燕龙'),(45,'传智播客','2018-03-04 12:04:06','男','北京金燕龙'),(46,'老王','2018-03-07 17:37:26','男','北京'),(48,'小马宝莉','2018-03-08 11:44:00','女','北京修正');
2.创建Maven项目并在pom.xml中导入依赖坐标
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.5</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
</dependencies>
3.在resources目录下创建log4j的配置文件log4j.properties（日志信息）
# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE debug info warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE
# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE
# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
4.创建与数据库表对应的User类，属性名和数据库表的字段名相同
package com.chenpeng.domain;
import java.io.Serializable;
import java.util.Date;
public class User implements Serializable {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday=" + birthday +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
}
5.编写持久层接口UserDao
package com.chenpeng.dao;
import com.chenpeng.domain.User;
import java.util.List;
public interface UserDao {
/**
* 查询所有用户
* @return
*/
List<User> findAll();
}
使用xml配置mybatis
1.在resources目录下创建mybatis配置文件SqlMapConfig.xml
<?xml version="1.0" encoding="UTF-8"?>
<!-- 引入Mybatis的xml约束 -->
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--Mybatis的主配置文件-->
<configuration>
<!--配置环境-->
<environments default="mysql">
<!--配置mysql的环境-->
<environment id="mysql">
<!--配置事务的类型-->
<transactionManager type="JDBC"></transactionManager>
<!--配置数据源(连接池)-->
<dataSource type="POOLED">
<!--连接数据库的信息，用于创建Connection对象-->
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/user"/>
<property name="username" value="root"/>
<property name="password" value="991105"/>
</dataSource>
</environment>
</environments>
</configuration>
2.通过配置文件实现持久层接口
把sql语句写进xml文件中,让Mybatis框架通过反射给我们提供持久层接口的实现类
1.创建映射配置文件
在resources目录下创建com/chenpeng/dao/UserDao.xml文件，xml文件的路径和文件名与包路径和类名 相同
<?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">
<!-- 编写实现持久层代码的sql语句，namespace属性dao层接口的全限定类名 -->
<mapper namespace="com.chenpeng.dao.UserDao">
<!-- id属性为实现的方法，resultType属性为封装结果集的实体类的全限定类名 -->
<select id="findAll" resultType="com.chenpeng.domain.User">
<!-- 在select标签内写sql语句，用于获取PreparedStatement对象 -->
select * from user
</select>
</mapper>
2.在mybatis配置文件SqlMapConfig.xml中添加mapper标签指定映射配置文件的位置
<!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->
<mappers>
<mapper resource="com/chenpeng/dao/UserDao.xml"/>
</mappers>
3.编写测试类
package com.chenpeng.test;
import com.chenpeng.dao.UserDao;
import com.chenpeng.domain.User;
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 java.io.InputStream;
import java.util.List;
public class MybatisTest {
public static void main(String[] args) throws Exception{
//1.读取配置文件
InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(in);
//3.使用工厂生产SqlSession对象
SqlSession session = factory.openSession();
//4.使用SqlSession创建Dao层的代理对象
UserDao userDao = session.getMapper(UserDao.class);
//5.使用代理对象执行方法
List<User> users = userDao.findAll();
for (User user : users) {
System.out.println(user);
}
//6.释放资源
session.close();
in.close();
}
}
使用注解配置mybatis
1.在持久层接口的方法上加上@Select注解，其value属性为该方法要执行的sql语句
public interface UserDao {
/**
* 查询所有用户
* @return
*/
@Select("select * from users")
List<User> findAll();
}
2.在mybatis配置文件SqlMapConfig.xml中修改mapper
<mappers>
<mapper class="com.chenpeng.dao.UserDao"/>
</mappers>
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