idea上MyBatis第一个例子

接着上面创建的maven项目来。

1.java目录下创建cn.happy.entity包

2.idea下创建数据库连接

配置连接参数

3.把数据库表变成实体类

导入成功，改一下包名就可以用了

4.新建cn.happy.dao包，在下面新建IUserDAO接口，代码如下

package cn.happy.dao;

import cn.happy.entity.Smbms_user;

import java.util.List;

public interface IUserDAO {
    List<Smbms_user> findAll();
}

5.在IUserDAO同包下新建IUserDAO.xml文件（俗称小配置），文件名一定要相同（这样做可以规避后面的一些问题）。

官方文档中找到

2.1.4 Exploring Mapped SQL Statements

把下面的文档直接粘贴到IUserDAO.xml里

<?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="org.mybatis.example.BlogMapper">
 <select id="selectBlog" parameterType="int" resultType="Blog">
 select * from Blog where id = #{id}
 </select>
</mapper>

修改包名和<mapper>节点，比如我的代码修改如下即可

<?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">
<!--关联接口的全限定名-->
<mapper namespace="cn.happy.dao.IUserDAO">
    <!--大配置中settings autoMappingBehavior NONE,所以数据库只会装配以下column-->
    <resultMap id="UserMapper" type="cn.happy.entity.Smbms_user">
        <id property="id" column="id"/>
        <result property="username" column="username"/>
        <result property="userpassword" column="userpassword"/>
    </resultMap>
    <!--id要与接口中的方法名相同-->
    <select id="findAll" resultMap="UserMapper">
        select * from smbms_user
    </select>
</mapper>

6.配置resources

这里需要配置三个文件

1.jdbc.properties

2.log4j.properties

3.mybatis-config.xml

jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql:///t14_smbms?characterEncoding=utf8&useSSL=true
jdbc.username=root
jdbc.password=root

log4j.properties

log4j.rootLogger=debug,stdout,file
### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### direct messages to file mylog.log ###
log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=c:\\logs\\log.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### set log levels - for more verbose logging change 'info' to 'debug' ###

log4j.logger.cn.happy.dao=debug, stdout,file

mybatis-config.xml,俗称大配置

<?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>
    <!--引入 jdbc.properties-->
    <properties resource="jdbc.properties"/>
    <settings>
        <setting name="logImpl" value="LOG4J"/>
        <setting name="autoMappingBehavior" value="NONE"/>
    </settings>
    <!--别名，这里不使用别名，一律使用全限定名-->
    <!--<typeAliases>
        <package name="cn.happy.entity"/>
    </typeAliases>-->
    <!--DB connection info,配置mybatis多套运行环境-->
    <environments default="development">
        <environment id="development">
            <!--采用jdbc事务管理-->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--大配置关联小配置-->
    <mappers>
        <!--关联单个小配置,不能重复关联-->
        <mapper resource="cn/happy/dao/IUserDAO.xml"/>
        <!--关联整个包,dao层接口名字和对应的xml名字要一样-->
        <!--<package name="cn.happy.dao"/>-->
    </mappers>
</configuration>

7.编写MyBatisUtil类

package cn.happy.util;

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;

public class MyBatisUtil {
    private static InputStream is;
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            is=Resources.getResourceAsStream("mybatis-config.xml");
        } catch (IOException e) {
            e.printStackTrace();
        }
        sqlSessionFactory= new SqlSessionFactoryBuilder().build(is);
    }
    private MyBatisUtil(){}
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

8.创建测试类

代码：

package cn.happy.test;

import cn.happy.dao.IUserDAO;
import cn.happy.entity.Smbms_user;
import cn.happy.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class Test20170916 {
    @Test
    public void findAll(){
        SqlSession session = MyBatisUtil.getSession();
        IUserDAO mapper = session.getMapper(IUserDAO.class);
        List<Smbms_user> users = mapper.findAll();
        for (Smbms_user user:users
             ) {
            System.out.println(user.getId()+"\t"+user.getUsername()+"\t"+user.getUserpassword());
        }
    }
}

 运行结果：