一、Springboot連接數(shù)據(jù)的方式主要有以下三種

• JDBC
• Mybatis
• Spring Data JPA

二、springboot整合JDBC

1.創(chuàng)建項目，引入stater

查看pom.xml，主要依賴已經(jīng)引入

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
 
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

2.編寫yml

spring:
  datasource:
    username: root
    password: root
    url: jdbc:mysql://localhost:3306/test2
    driver-class-name: com.mysql.jdbc.Driver

3.修改測試類進(jìn)行測試

@SpringBootTest
class SpringbootJdbcApplicationTests {

    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
        Connection connection = dataSource.getConnection();
        System.out.println("connection:" + connection);
        connection.close();
    }

}

輸出:

connection:HikariProxyConnection@1054913783 wrapping com.mysql.cj.jdbc.ConnectionImpl@79b84841

springboot 默認(rèn)可以支持Dbcp2，Hikari，Tomcat（springboot 2.2.5）等數(shù)據(jù)源
相關(guān)配置在DataSourceConfiguration類中
4.使用JdbcTemplate操作數(shù)據(jù)庫
創(chuàng)建Controller

代碼如下：

@RestController
@RequestMapping("/hello")
public class HelloController {
    @Autowired
    JdbcTemplate jdbcTemplate;

    @GetMapping("/score")
    public Map<String, Object> getScore() {
        List<Map<String, Object>> scoreList = jdbcTemplate.queryForList("SELECT * FROM score");
        return scoreList.get(0);
    }

}

數(shù)據(jù)庫表數(shù)據(jù)：

查詢結(jié)果如下：

5.如何修改數(shù)據(jù)源
性能方面 hikari>druid>tomcat-jdbc>dbcp>c3p0 。hikari的高性能得益于最大限度的避免鎖競爭。druid功能最為全面，sql攔截等功能，統(tǒng)計數(shù)據(jù)較為全面，具有良好的擴(kuò)展性。
上面的開發(fā)中可以看到我們使用的數(shù)據(jù)源為hikari，接下來我們要將其修改為durid
(1)首先加入如下依賴

<!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.20</version>
</dependency>

（2）修改pom文件，加入type: com.alibaba.druid.pool.DruidDataSource

spring:
  datasource:
    username: root
    password: root
    url: jdbc:mysql://localhost:3306/test2
    driver-class-name: com.mysql.cj.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource

(3)測試類進(jìn)行測試

@SpringBootTest
class SpringbootJdbcApplicationTests {

    @Autowired
    DataSource dataSource;

    @Test
    void contextLoads() throws SQLException {
        System.out.println(dataSource.getClass());
    }
}

輸出：

class com.alibaba.druid.pool.DruidDataSource

(4)更全面的連接池配置

spring:
  datasource:
    username: root
    password: root
    url: jdbc:mysql://localhost:3306/test2
    driver-class-name: com.mysql.cj.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource
    initialSize: 1 #初始化大小
    minIdle: 1 #最小等待連接數(shù)量
    # maxIdle: 5 最大等待連接數(shù)量,已經(jīng)被棄用，報錯：maxIdle is deprecated
    maxActive: 20 #最大連接數(shù)
    maxWait: 60000 #配置獲取連接等待超時的時間
    timeBetweenEvictionRunsMillis: 60000 #間隔多久才進(jìn)行一次檢測，檢測需要關(guān)閉的空閑連接，單位是毫秒
    minEvictableIdleTimeMillis: 300000 # 配置一個連接在池中最小生存的時間，單位是毫秒
    # Oracle必須這樣配置檢查，不了會報檢查錯誤
    validationQuery: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: true
    testOnReturn: false
    # 打開PSCache，并且指定每個連接上PSCache的大小
    poolPreparedStatements: false
    maxPoolPreparedStatementPerConnectionSize: 20
    # 配置監(jiān)控統(tǒng)計攔截的filters，去掉后監(jiān)控界面sql無法統(tǒng)計，'wall'用于防火墻
    filters: stat,wall,log4j
    # 通過connectProperties屬性來打開mergeSql功能；慢SQL記錄
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
    # 合并多個DruidDataSource的監(jiān)控數(shù)據(jù)
    useGlobalDataSourceStat: true

druid:
  allow: #允許登陸的IP地址
    ip: 127.0.0.1
  login: #登陸的賬戶密碼
    userName: admin
    password: admin123

為了使上面連接池配置生效，需要添加duridConfig配置文件

@Configuration
public class DuridConfig {
    @Value("${druid.login.userName}")
    private String userName;

    @Value("${druid.login.password}")
    private String password;

    @Value("${druid.allow.ip}")
    private String allowIp;

    @ConfigurationProperties(prefix = "spring.datasource")
    @Bean
    public DataSource druid() {
        return new DruidDataSource();
    }

    //配置durid的監(jiān)控
    //1.配置一個管理后臺的servlet
    @Bean
    public ServletRegistrationBean statViewServlet() {
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean();
        servletRegistrationBean.setServlet(new StatViewServlet());
        servletRegistrationBean.addUrlMappings("/druid/*");
        Map<String, String> initParameters = new HashMap<>();
        initParameters.put("loginUsername", userName); // 用戶名
        initParameters.put("loginPassword", password); // 密碼
        initParameters.put("resetEnable", "false");    // 禁用HTML頁面上的“Reset All”功能
        initParameters.put("allow", allowIp); // IP白名單 (沒有配置或者為空，則允許所有訪問)
        //initParameters.put("deny", "");// IP黑名單 (存在共同時，deny優(yōu)先于allow)
        servletRegistrationBean.setInitParameters(initParameters);
        return servletRegistrationBean;
    }

    //2.注冊一個web監(jiān)控的filter
    @Bean
    public FilterRegistrationBean filterRegistrationBean() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(new WebStatFilter());
        filterRegistrationBean.addUrlPatterns("/*");
        filterRegistrationBean.addInitParameter("exclusions", "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
        return filterRegistrationBean;
    }
}

瀏覽器訪問：http://127.0.0.1:8080/druid