Mybatis的使用以及快速入门

基本配置

（1）mybatis-config.xml

<?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>


<properties resource="db.properties">
<property name="username" value="root"/>
<property name="password" value="123"/>
</properties>


<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
<setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>




<typeAliases>

</typeAliases>

<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>

<mappers>
<mapper class="com.kuang.dao.BlogMapper"/>
</mappers>

</configuration>

(2)db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8

(3)MybatisUtils

package com.kuang.utils;

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.IOException;
import java.io.InputStream;

//sqlSessionFactory -->sqlSession

public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
static {

InputStream inputStream = null;
try {
// 使用Mybatis第一步：获取sqlSessionFactory对象
String resource = "mybatis-config.xml";
inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}

}
// 获取salSessionFactory，完全包含了面向数据库执行SQL命令所需的所有方法
public static SqlSession getSqlSession(){
SqlSession sqlSession = sqlSessionFactory.openSession();
return sqlSession;
}
}

(4)pom 文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.kuang</groupId>
<artifactId>Mybatis-Study</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
<module>Mybatis-01</module>
<module>mybatis-02</module>
<module>mybatis-03</module>
<module>mybatis-06</module>
<module>mybatis-08</module>
<module>mybatis-09</module>
<module>mybatis-10</module>
<module>mybatis-15</module>
</modules>


<dependencies>

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>


<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>

<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>

</dependency>
</dependencies>
、
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>

</project>

二、注解的方式(与SQL有关)

（1）CRUD

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.kuang.dao.UserMapper">

<cache type="org.mybatis.caches.ehcache.EhcacheCache"/>
<select id="querUserById" resultType="User">
select * from user where id=#{id}
</select>
</mapper>

UserMapper.xml文件。这里面主要写的是sql，现在我们来看一下，

namespace为所引用的接口，这里相当于UserMapper.

id,相当于这个UserMapper中方法的名字

resultType为返回的类型，parameterType为参数的类型

多对一

现在我们需要查询学生和老师的相关信息