IDEA中Maven工程的MyBatis快速入门

Java sxdgy 222℃

1.创建maven工程

Create New Project–>Maven–>勾选create from archetype–>maven archetype quickstart–>……

2.添加jar包坐标

在pom.xml中添加如下依赖包:

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.4.5</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.6</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.12</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
</dependencies>

3.编写实体类

Mybitis使用了ORM(Object Relational Mappging 对象关系映射)思想,即要求数据库表字段和实体类属性相对应。假如数据库有一个User表为:

CREATE TABLE `user` (
`id` int(11) NOT NULL auto_increment,
`username` varchar(32) NOT NULL COMMENT '用户名',
`sex` char(1) default NULL COMMENT '性别',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert into `user`(`id`,`username`,`sex`) values (41,'老王','男'),(42,'二王','女');

需要创建的User类具有相同的数表字段名,同时需要实现Serializable接口,放在src/main/java下,代码如下:

package com.gqzzw.domain;

import java.io.Serializable;

public class User implements Serializable {
    private Integer id;
    private String userName;
    private String sex;

    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 String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

4.编写实体类的持久层映射接口

这里对应的User类持久层映射接口取名UserMapper,放在src/main/java下,代码如下:

package com.gqzzw.mapper;

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

public interface UserMapper {
    //查询所有用户
    List<User> findAll();
}

5.编写映射接口的配置文件

放在src/main/resources下,必须与久层接口包路径和文件名相同,即:com.gqzzw.mapper.UserMapper.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.gqzzw.mapper.UserMapper">
    <!-- 配置SQL语句 -->
    <select id="findAll" resultType="com.gqzzw.domain.User">
        select * from user
    </select>
</mapper>

6.编写MyBatis主配置文件

放在src/main/resources下,新建SqlMapConfig.xml,内容如下:

<?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>
    <!-- 环境配置列表 -->
    <environments default="local">
        <!-- 环境配置 -->
        <environment id="local">
            <!-- 事务类型 -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 数据源(连接池) -->
            <dataSource type="POOLED">
                <!-- 连接mysql四要素 -->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 映射配置文件位置 -->
    <mappers>
        <mapper resource="com/gqzzw/dao/UserDao.xml"></mapper>
    </mappers>
</configuration>

7.编写log4j的配置文件

放在src/main/resources下,新建log4j.properties,内容如下:

#设置日志的级别,输出目的
log4j.rootLogger=DEBUG, stdout
#设置输出目的地为控制台
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
#布局为PatternLayout,可灵活地指定布局模式。
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
#设置输出格式
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

8.编写测试类

放在src/test/java下,编写测试类,内容如下:

package com.gqzzw.mapper;

import com.gqzzw.domain.User;
import com.gqzzw.mapper.UserMapper;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class UserMapperTset {
 @Test
 public void test() throws IOException {
 //1.读取配置文件
 InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
 //2.创建SqlSessionFactory的构建者对象
 SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
 //3.使用构建者创建工厂对象SqlSessionFactory
 SqlSessionFactory factory = builder.build(in);
 //4.使用SqlSessionFactory生产SqlSession对象
 SqlSession sqlSession = factory.openSession();
 //5.使用SqlSession创建映射接口的代理对象
 UserMapper mapper = sqlSession.getMapper(UserMapper.class);
 //6.使用代理对象执行查询所有方法
 List<User> users = mapper.findAll();
 //7.遍历集合
 for (User user : users) {
 System.out.println(user);
 }
//8.释放资源
        sqlSession.close();
        in.close();
 }
}

9.使用Junit测试

测试结果类似如下代表成功:

DEBUG [main] - ==>  Preparing: select * from user 
DEBUG [main] - ==> Parameters: 
DEBUG [main] - <==      Total: 2
User{id=41, username='老王', sex=男}
User{id=42, username='二王', sex=女}

10.使用注解(可选)

移除映射接口的配置文件UserMapper.xml,修改主配置文件的映射配置为:

<!-- 映射配置文件位置 -->
    <mappers>
      <mapper class="com.gqzzw.mapper.UserMapper"/>
    </mappers>

再在实体类映射接口UserMapper.class的方法上添加@Select注解:

package com.gqzzw.mapper;

import com.gqzzw.domain.User;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface UserMapper {
    //查询所有用户
    @Select("select * from user")
    List<User> findAll();
}

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