Spring Boot 数据访问

application.yami配置

引入依赖包druid-spring-boot-starter

<dependency>
   <groupId>com.alibaba</groupId>
   <artifactId>
       druid-spring-boot-starter
   </artifactId>
   <version>1.2.8</version>
</dependency>
<!--导入驱动-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>
        mysql-connector-java
    </artifactId>
    <version>8.0.26</version>
</dependency>

①配置文件配置MySQL接口和数据库驱动Driver

# 配置数据库连接
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test
    username: gcs
    password: 273869
    driver-class-name: com.mysql.cj.jdbc.Driver

②利用JdbcTemplate调用sql语句

#在方法里放入执行语句
jdbcTemplate.execute("select * from user");

mybatis.xml+Mapper.xml

引入依赖包mybatis-spring-boot-starter

<dependency>
  <groupId>org.mybatis.spring.boot</groupId>
  <artifactId>
      mybatis-spring-boot-starter
   </artifactId>
   <version>2.2.0</version>
</dependency>
<!--导入驱动-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>
        mysql-connector-java
    </artifactId>
    <version>8.0.26</version>
</dependency>

①创建mybatis.xml配置文件

<?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">
<configuration>
   <environments default="development">
   <environment id="development">
   <transactionManager type="JDBC"/>
   <dataSource type="POOLED">
   <property          
       name="driver"
       value="com.mysql.jdbc.Driver"/>
   <property 
       name="url"
       value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=utf8"/>
   <property name="username" value="gcs"/>
   <property name="password" value="273869"/>
   </dataSource>
   </environment>
   </environments>
   <mappers>
   <mapper    resource="com/example/spring_mybatis/mapper/userMapper.xml"/>
        
</configuration>

②创建接口Mapper

@Mapper
public interface AccountMapper{
    #构建方法
    public Account getAccount(String name);
}

③创建mapper配置文件Mapper.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.example.managesystemdemo.mapper.AccountMapper">
    
<!--id为Mapper接口里面的方法名,namespace为Mapper接口的地址-->
   <select id="getAccount" resultType="com.example.managesystemdemo.bean.Account">
    select * from user where username=#{name}
    </select>

</mapper>

④为Mapper接口创建服务接口和实现类

@Data
@Component
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class Account {
    private  String username;
    private  String pwd;
}

public interface AccountService {

    public Account getUser(String name);
}

@Service
public class AccountServiceImpl 
             implements AccountService {

    @Autowired
    AccountMapper accountMapper;

    public Account getUser(String name) {
        //调用mapper接口方法
        return accountMapper.getAccount(name);
    }

}

⑤利用服务接口实现数据访问

@Autowired
AccountService accountService;

@ResponseBody
@GetMapping("/select")
public Account select(@RequestParam String name
    {
        return accountService.getUser(name);
    }

Mapper接口+注释

引入依赖包导入mybatis-plus包,自带jdbc驱动,所以不需要导入驱动包mysql-connector-java

<dependency>
   <groupId>com.baomidou</groupId>
   <artifactId>
       mybatis-plus-boot-starter
   </artifactId>
   <version>3.4.1</version>
 </dependency>

①创建Mapper接口

public interface AccountMapper {
    /**
     * 有@Insert注释就不需要配置mapper.xml文件了
     */
    @Insert("insert into user 
    values(#{username},#{pwd})")
    public void insertAccount(Account account);
}

②创建服务接口和实现类

@Data
@Component
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class Account {
    private  String username;
    private  String pwd;
}


public interface AccountService {

    public void insertAccount(Account account);
}

@Service
public class AccountServiceImpl 
             implements AccountService {

    @Autowired
    AccountMapper accountMapper;

    @Override
    public void insertAccount(Account account)
    {
        //调用mapper接口方法
        accountMapper.insertAccount(account);
    }

}

③利用服务类访问数据

City city = new City("上饶","江西","中国");

@Autowired
AccountService accountService;

@ResponseBody
@GetMapping("/insert")
public String insert()
   {
        cityService.insert(city);
        return "{city.toString()}插入成功！！！";
    }

BaseMapper+@TableName()

引入依赖mybatis-plus

<dependency>
   <groupId>com.baomidou</groupId>
   <artifactId>
       mybatis-plus-boot-starter
   </artifactId>
   <version>3.4.1</version>
 </dependency>

①创建数据表映射的类

@Data
@Component
@ToString
@NoArgsConstructor
@AllArgsConstructor
//默认表名为类名小写
@TableName("user_info")
public class User {
 //所有属性都应该在数据表中，属性名和表中字段名相同
 //除了有TableField(exist =   false)注释的
    
    //默认主键为自增，如果主键不是自增得说明，不然会报错
    @TableId(type = IdType.AUTO)
    private String username;

    @TableField(exist = false)
    //表中没有该属性对应的字段名
    private String password;

    private String fullname;
    private String email;
    private String address;
    private String city;
    private String sex;
}

②创建Mapper接口

/**
 * 继承BaseMapper就有操作数据库的方法，不需要写Mapper.xml
 */
@Mapper
public interface UserMapper extends BaseMapper<User> {


}

③创建服务接口和实现类

/**
 * 继承IService<User>类，里面有所有的MySQL执行方法
 */
public interface UserService extends IService<User> {
    
}


/**
 * 继承ServiceImpl<UserMapper,User>类就不需要重写   
 * IService接口里面的所有方法
 */
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

}

④利用服务接口访问数据

@Autowired
UserService userService;

@ResponseBody
    @GetMapping("/userInfo")
    public List<User> getUserInfo()
    {
        //BaseMapper<>类自带很多MySQL执行方法
        return userService.list();
    }