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());
     }
 }