【Mybatis】手把手搭建Mybatis环境并实现数据库读取

一、创建数据库

这里我将数据库命名为mybatis
数据库如下：

DROP TABLE IF EXISTS `user`;

CREATE TABLE `user` (   `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`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `user`(`id`,`username`,`birthday`,`sex`,`address`) values (41,'老王','2018-02-27 17:47:08','男','北京'),(42,'小二王','2018-03-02 15:09:37','女','北京金燕龙'),(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');

DROP TABLE IF EXISTS `account`;

CREATE TABLE `account` (   `ID` int(11) NOT NULL COMMENT '编号',   `UID` int(11) default NULL COMMENT '用户编号',   `MONEY` double default NULL COMMENT '金额',   PRIMARY KEY  (`ID`),   KEY `FK_Reference_8` (`UID`),   CONSTRAINT `FK_Reference_8` FOREIGN KEY (`UID`) REFERENCES `user` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `account`(`ID`,`UID`,`MONEY`) values (1,41,1000),(2,45,1000),(3,41,2000);

DROP TABLE IF EXISTS `role`;

CREATE TABLE `role` (   `ID` int(11) NOT NULL COMMENT '编号',   `ROLE_NAME` varchar(30) default NULL COMMENT '角色名称',   `ROLE_DESC` varchar(60) default NULL COMMENT '角色描述',   PRIMARY KEY  (`ID`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `role`(`ID`,`ROLE_NAME`,`ROLE_DESC`) values (1,'院长','管理整个学院'),(2,'总裁','管理整个公司'),(3,'校长','管理整个学校');

DROP TABLE IF EXISTS `user_role`;

CREATE TABLE `user_role` (   `UID` int(11) NOT NULL COMMENT '用户编号',   `RID` int(11) NOT NULL COMMENT '角色编号',   PRIMARY KEY  (`UID`,`RID`),   KEY `FK_Reference_10` (`RID`),   CONSTRAINT `FK_Reference_10` FOREIGN KEY (`RID`) REFERENCES `role` (`ID`),   CONSTRAINT `FK_Reference_9` FOREIGN KEY (`UID`) REFERENCES `user` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `user_role`(`UID`,`RID`) values (41,1),(45,1),(41,2);

二、Mybatis环境搭建

1.创建Maven项目

注意：如果是第一次，要勾选Create from archetype，选择其中的quickstart导入一些必要的库。否则在写依赖时可能出现红色下划线报错not found。若已经初始化过，可以不勾选直接开始。

总目录结构

2.在pom.xml中添加如下依赖

<dependencies> 
	<dependency> 
		<groupId>org.mybatis</groupId> 
		<artifactId>mybatis</artifactId> 
		<version>3.4.5</version> 
	</dependency> 
	<dependency> 
		<groupId>junit</groupId> 
		<artifactId>junit</artifactId> 
		<version>4.10</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.编写User实体类

package com.surong.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 + '\'' +
                '}';
    }
}

4.编写持久层接口UserDao

package com.surong.dao;

import com.surong.domain.User;
import java.util.List;
/*
 *用户的持久层接口
 */
public interface UserDao {

    //查询所有
    List<User> findAll();

}

5.编写持久层接口的映射文件UserDao.xml

<?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="com.surong.dao.UserDao">
    <!-- 配置查询所有操作 -->
    <select id="findAll" resultType="com.surong.domain.User"> <!--方法名和类名-->
        select * from user
    </select>
</mapper>

6.编写 SqlMapConfig.xml 配置文件并添加log4j.properties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">
<!--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>
            <!--配置连接池-->
            <dataSource type="POOLED">
                <!--配置连接数据库的四个基本信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>

        </environment>
    </environments>

    <mappers>
        <mapper resource="com/surong/dao/UserDao.xml"/>
    </mappers>

</configuration>

lo4j.properties

# 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

7.编写测试类MybatisTest

package com.surong.test;

import com.surong.dao.UserDao;
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;

import java.util.List;
import com.surong.domain.User;

import javax.xml.transform.Source;

public class MybatisTest {

    public static void main(String[] args) throws IOException {
        //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SqlSessionFactory
        SqlSession session = factory.openSession();

        //4.使用SqlSessionFactory创建Dao接口的代理对象
        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();

    }
}

8.编译链接
结果如下：

注意：可能出现如下错误
1.不再支持源选项 1.5。请使用 1.6 或更高版本
查看链接：

2.Unknown DataSource property: url
检查第6步SqlMapConfig.xml 文件中DataSource里的property的url有没写错，要写你创建的数据库的名字。

三、基于注解的Mybatis的使用

目录结构

1.移除 第五步中xml 的映射配置（UserDao.xml）

2.在持久层接口UserDao中添加注解

package com.surong.dao;
 
import com.surong.domain.User;
import org.apache.ibatis.annotations.Select;
 
import java.util.List;
/*
*用户的持久层接口
*/
public interface UserDao{
 
//查询所有
@Select("select * from user")
	List<User> findAll();
 
}

3.修改 SqlMapConfig.xml中的mapper

<mappers>
	<mapper class="com.surong.dao.UserDao"/>
</mappers>