对于数据访问层，无论是SQL还是NOSQL，Spring Boot默认采用整合
Spring Data的方式进行统一处理，添加大量自动配置，屏蔽了很多设置。引入各种xxxTemplate，xxxRepository来简化我们对数据访问层的操作。对我们来说只需要进行简单的设置即可。

整合基本JDBC与数据源

1、引入starter和MySQL驱动

<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、配置application.yml

spring:
  datasource:
    username: root
    password:
    url: jdbc:mysql://localhost:3306/springboot_jdbc?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
    driver‐class‐name: com.mysql.cj.jdbc.Driver

3、测试

@RunWith(SpringRunner.class)
@SpringBootTest
public class HahaApplicationTests {
    @Autowired
    DataSource dataSource;
    @Test
    public void contextLoads() throws SQLException {
        //class com.zaxxer.hikari.HikariDataSource默认数据源
        System.out.println("------------"+dataSource.getClass());

class com.zaxxer.hikari.HikariDataSource作为默认数据源
数据源的相关配置都在DataSourceProperties里面；
自动配置原理：
org.springframework.boot.autoconfigure.jdbc：
1、参考DataSourceConfiguration，根据配置创建数据源，可以使用
spring.datasource.type配置指定自定义的数据源类型；
2、SpringBoot默认可以支持；

org.apache.tomcat.jdbc.pool.DataSource、HikariDataSource、BasicDataSource、

3、DataSourceInitializer：ApplicationListener；
作用：
1）、runSchemaScripts();运行建表语句；
2）、runDataScripts();运行插入数据的sql语句；
默认只需要将文件命名为：

spring:
  datasource:
    username: root
    password:
    url: jdbc:mysql://localhost:3306/springboot_jdbc?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
    driver‐class‐name: com.mysql.cj.jdbc.Driver
	schema‐*.sql、data‐*.sql
	默认规则：schema.sql，schema‐all.sql；
	initialization-mode: always
	schema:
		‐ classpath:department.sql
	指定位置

springboot2.0x 执行schema.sql脚本注意要加上一个配置：spring.datasource.initialization-mode=always
表示始终执行初始化。
4、操作数据库：自动配置了JdbcTemplate操作数据库

@Controller
public class HelloController {

    @Autowired
    JdbcTemplate jdbcTemplate;

    @GetMapping("/hello")
    @ResponseBody
    public Map<String,Object> haha(){
        List<Map<String, Object>> list = jdbcTemplate.queryForList("select * from emp");
        return list.get(0);
    }

}

4、整合Druid数据源

1、引入依赖

		<!-- Druid数据源 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.20</version>
        </dependency>

2、配置application.yml

spring:
  datasource:
    #   数据源基本配置
    username: root
    password:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url:  jdbc:mysql://localhost:3306/mybatis?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
    type: com.alibaba.druid.pool.DruidDataSource
    #   数据源其他配置
    initialSize: 5
    minIdle: 5
    maxActive: 20
    maxWait: 60000
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQuery: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    #   配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
    filters: stat,wall,slf4j
    maxPoolPreparedStatementPerConnectionSize: 20
    useGlobalDataSourceStat: true
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
#    schema:
#      - classpath:mysql/department.sql
#      - classpath:mysql/employee.sql
#    initialization-mode: always

3、编写Druid的配置文件，并实现后台监控

@Configuration
public class DruidCongig {

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

    //配置Druid监控
    //配置一个管理后台的servlet
    @Bean
    public ServletRegistrationBean statViewServlet(){
        ServletRegistrationBean bean = new ServletRegistrationBean(new StatViewServlet(), "/druid");

        Map<String,String> map =new HashMap<>();
        map.put("loginUsername","admin");
        map.put("loginPassword","123");
        map.put("allow","");//允许所有访问
        map.put("deny","");
        bean.setInitParameters(map);
        return bean;
    }
    //配置一个web监控的filter
    @Bean
    public FilterRegistrationBean webStatFilter(){
//        FilterRegistrationBean bean = new FilterRegistrationBean(new WebStatFilter());
//        Map<String,String> map =new HashMap<>();
//        map.put("exclusions","*.js,*.css,/druid/*");//允许通过
//        bean.setInitParameters(map);
//        bean.setUrlPatterns(Arrays.asList("/*"));
//        return bean;

        FilterRegistrationBean bean = new FilterRegistrationBean();
        bean.setFilter(new WebStatFilter());

        Map<String,String> initParams = new HashMap<>();
        initParams.put("exclusions","*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");

        bean.setInitParameters(initParams);

        bean.setUrlPatterns(Arrays.asList("/*"));

        return  bean;
    }


}