springboot学习（九） 使用mybatis访问数据库

1、添加maven依赖

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.1</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>6.0.6</version>
</dependency>

　　这里使用的是mysql数据库，如果是其他数据库将数据库依赖换掉即可。

2、修改配置文件

　　在application.properties配置文件中增加mybatis的数据库连接配置：

# 定义注解类所在的包
mybatis.type-aliases-package=cn.origal.domain

spring.datasource.url=jdbc:mysql://localhost:3309/test?serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

3、修改启动类

　　在启动类中增加项目对mapper包的扫描：

@SpringBootApplication
@MapperScan("cn.origal.mapper")
public class Application {

    public static void main(String[] args) {
        SpringApplication application = new SpringApplication(Application.class);
        // 取消通过命令行设置属性值
        application.setAddCommandLineProperties(false);
        application.run(Application.class, args);
    }
}

4、开发mapper类连接测试

　　user实体类：

package cn.origal.domain;

public class User {

    private String name;

    private Integer age;

    //  .....  
}

　　mapper类：

package cn.origal.mapper;

import cn.origal.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserMapper {

    @Insert("insert into user(name, age) values (#{name}, #{age})")
    void insert(User user);

    @Update("update user set age=#{age} where name=#{name}")
    void update(User user);

    @Delete("delete from user where name=#{name}")
    void delete(User user);

    @Select("select name, age from user")
    @Results({
            @Result(property = "name",  column = "name"),
            @Result(property = "age", column = "age")
    })
    List<User> getAll();
}

　　测试类：

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class TestMybatis {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testInsert() {
        User user = new User();
        user.setName("a2");
        user.setAge(11);

        userMapper.insert(user);
    }

    @Test
    public void query() {
        System.out.println(userMapper.getAll());
    }
}

5、通过xml文件连接测试

　　（1）首先在上面的那些配置还是需要的，然后在application.properties配置文件中添加xml文件配置：

# 定义注解类所在的包
mybatis.config-locations=classpath:mybatis/mybatis-config.xml
mybatis.mapper-locations=classpath:mybatis/mapper/*.xml

　　目录结构：

　　（2）在mybatis配置mybatis-config.xml中添加一些基础配置：

<?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>
    <typeAliases>
    </typeAliases>
</configuration>

　　（3）添加User的映射文件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="cn.origal.mapper.UserXmlMapper">

    <select id="getAll" resultType="User">
        SELECT
        name, age
        FROM user
    </select>
</mapper>

　　（4）编写对应的dao层：

package cn.origal.mapper;

import cn.origal.domain.User;

import java.util.List;

public interface UserXmlMapper {

    List<User> getAll();
}

　　（5）进行连接测试：

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class TestXmlMybatis {

    @Autowired
    private UserXmlMapper userXmlMapper;

    @Test
    public void test() {
        System.out.println(userXmlMapper.getAll());
    }
}