通过springboot操作读写数据库，首先在pom.xml引入对应的依赖jar包

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.10</version>
</dependency>
<!--通用mapper-->
<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper-spring-boot-starter</artifactId>
    <version>2.1.5</version>
</dependency>
<!-- 数据库驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.19</version>
</dependency>
<!-- oracle ojdbc -->
<dependency>
    <groupId>oracle</groupId>
    <artifactId>ojdbc6</artifactId>
    <version>11.2.0.3</version>
</dependency>

然后进入application.properties，写入链接数据库的地址

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://IP:3306/canace?useUnicode=true&characterEncoding=UTF-8&useSSL=false&allowMultiQueries=true
spring.datasource.username=root
spring.datasource.password=(密码)

创建数据库连接池

private static DruidDataSource dataSource;
    static {
        Properties properties = ProPertiesUtil.getProperties("application.properties");
        // 使用德鲁伊数据库连接池工厂类
        try {
            dataSource = (DruidDataSource) DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

获取链接对象

/**
     * 获取连接对象（从数据库连接池中获取）
     * @return 连接对象
     */
    public static Connection getConnection() {
        Connection connection = null;
        try {
            connection = dataSource.getConnection();
        } catch (Exception e) {
            return null;
        }
        return connection;
    }

通过sql语句写入mysql数据库（QueryRunner模式）

public void addUser(userAllModel use) {
        //创建QueryRunner 对象
        QueryRunner queryRunner = new QueryRunner();
        //获取Connection连接
        Connection connection = JDBCUtil.getConnection();
        //定义sql语句
        String sql = "insert into user(username,description,content) values(?,?,?)";
        try {
            int update = queryRunner.update(connection, sql, use.getUsername(), use.getDescription(), use.getContent());
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtil.close(connection);
        }
    }

查询语句，结果返回格式是Map集合

public String selectLast() {
        //创建QueryRunner 对象
        QueryRunner queryRunner = new QueryRunner();
        //获取Connection连接
        Connection connection = JDBCUtil.getConnection();
        //定义sql语句
        String sql = "select * from user order by id desc limit 1";
        try {
            //这条记录返回Map集合
            Map<String, Object> objectMap = queryRunner.query(connection, sql, new MapHandler());
            return JSON.toJSONString(objectMap);
        } catch (SQLException e) {
            e.printStackTrace();
        } 
        return null;
    }

第二、下面是DriverManager的链接方式：

static String driverClass = "oracle.jdbc.driver.OracleDriver"; //oracle的驱动
static String url = "jdbc:oracle:thin:@IP:1521:ORCL";  //连接oracle
static String user = "System";   //user是数据库的用户名
static String password = "123456";  //用户登录密码

 public static Connection getconn() {  //为了方便下面的讲解，这里专门建立了一个用于数据库连接的一个方法
        Connection conn = null;
        try {
            Class.forName(driverClass);//首先建立驱动
            conn = DriverManager.getConnection(url, user, password);  //驱动成功后进行连接
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn; //返回一个连接
    }

    public List<UserModel> selectAll() {
        List<UserModel> uselist = new ArrayList<UserModel>();
        try {
            Connection conn = getconn();
            Statement st = conn.createStatement();
            //创建sql查询语句
            String querySQL = "SELECT * FROM \"C##CCTEST\".T_USER";
            //执行sql语句并且换回一个查询的结果集
            ResultSet rs = st.executeQuery(querySQL);
            while (rs.next()) {  //循环遍历结果集
                UserModel use = new UserModel();
                int id = rs.getInt("id");
                String userid = rs.getString("userid");
                use.setID(id);
                use.setUSERID(userid);
                uselist.add(use);
            }
            st.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return uselist;
    }

第三、Mapper的方式：

<?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.pamirs.agent.httptest.demo.mapper.UserMapper">
    <resultMap id="BaseResultMap" type="com.pamirs.agent.httptest.demo.entity.User">
        <id column="id" jdbcType="BIGINT" property="id"/>
        <result column="name" jdbcType="VARCHAR" property="name"/>
        <result column="description" jdbcType="VARCHAR" property="description"/>
    </resultMap>

    <select id="selectByPrimaryKey" parameterType="java.lang.Long" resultMap="BaseResultMap">
        select
        <include refid="Base_Column_List"/>
        from user where id = #{id,jdbcType=BIGINT}
    </select>
</mapper>

3】java的UserMapper下面方法与resources的id名称一致。

@Component
public interface UserMapper {
    User selectByPrimaryKey(Long id);
}

4】创建方法，调用UserMapper

@Resource
private UserMapper userMapper;
@Override
public User getUserById(Long id) {
   return userMapper.selectByPrimaryKey(id);
}

5】在application.properties中添加mybatis.typeAliasesPackage和mybatis.mapperLocations，typeAliasesPackage=java下面mapper的绝对路径。

mybatis.mapperLocations=classpath*:/mapper/*.xml
mybatis.typeAliasesPackage=com.pamirs.agent.httptest.demo

6】在启动类里面添加启动项，MapperScan对应java下面mapper的绝对路径。

@SpringBootApplication
@MapperScan("com.pamirs.agent.httptest.demo.mapper")
public class HttpApplication {
    public static void main(String[] args) {
        SpringApplication.run(HttpApplication.class, new String[]{"--spring.profiles.active=c"});
    }
}