Druid是一个关系型数据库连接池，它是阿里巴巴的一个开源项目。Druid支持所有JDBC兼容数据库，包括了Oracle、MySQL、PostgreSQL、SQL Server、H2等。
Druid在监控、可扩展性、稳定性和性能方面具有明显的优势。通过Druid提供的监控功能，可以实时观察数据库连接池和SQL查询的工作情况。使用Druid连接池在一定程度上可以提高数据访问效率。

引入依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.0.29</version>
</dependency>

添加配置

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8
    username: root
    password: root
    #最大活跃数
    maxActive: 20
    #初始化数量
    initialSize: 1
    #最大连接等待超时时间
    maxWait: 60000
    #打开PSCache，并且指定每个连接PSCache的大小
    poolPreparedStatements: true
    maxPoolPreparedStatementPerConnectionSize: 20
    #通过connectionProperties属性来打开mergeSql功能；慢SQL记录
    #connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQuery: select 1 from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    #配置监控统计拦截的filters，去掉后监控界面sql将无法统计,'wall'用于防火墙
    filters: stat, wall, log4j
  jpa:
    properties:
      hibernate:
        show_sql: true
        format_sql: true

开启监控

添加Druid的filter

@Configuration
public class DruidConfiguration {

    @Bean
    public ServletRegistrationBean startViewServlet() {
        // 创建servlet注册实体
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(new StatViewServlet(),
                "/druid/*");
        // 设置ip白名单
        servletRegistrationBean.addInitParameter("allow", "127.0.0.1");
        // 设置ip黑名单，如果allow与deny共同存在时,deny优先于allow
        servletRegistrationBean.addInitParameter("deny", "192.168.0.19");
        // 设置控制台管理用户
        servletRegistrationBean.addInitParameter("loginUsername", "druid");
        servletRegistrationBean.addInitParameter("loginPassword", "123456");
        // 是否可以重置数据
        servletRegistrationBean.addInitParameter("resetEnable", "false");
        return servletRegistrationBean;
    }

    @Bean
    public FilterRegistrationBean statFilter() {
        // 创建过滤器
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(new WebStatFilter());
        // 设置过滤器过滤路径
        filterRegistrationBean.addUrlPatterns("/*");
        // 忽略过滤的形式
        filterRegistrationBean.addInitParameter("exclusions", "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
        return filterRegistrationBean;
    }
}

多数据源

数据源配置

spring:
  datasource:
    user:
      type: com.alibaba.druid.pool.DruidDataSource
      url: jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver
      filters: stat
      maxActive: 20
      initialSize: 1
      maxWait: 60000
      minIdle: 1
      timeBetweenEvictionRunsMillis: 60000
      minEvictableIdleTimeMillis: 300000
      validationQuery: select 'x'
      testWhileIdle: true
      testOnBorrow: false
      testOnReturn: false
      poolPreparedStatements: true
      maxOpenPreparedStatements: 20
    book:
      type: com.alibaba.druid.pool.DruidDataSource
      url: jdbc:mysql://127.0.0.1:3306/books?characterEncoding=utf8
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver
      filters: stat
      maxActive: 20
      initialSize: 1
      maxWait: 60000
      minIdle: 1
      timeBetweenEvictionRunsMillis: 60000
      minEvictableIdleTimeMillis: 300000
      validationQuery: select 'x'
      testWhileIdle: true
      testOnBorrow: false
      testOnReturn: false
      poolPreparedStatements: true
      maxOpenPreparedStatements: 20
  jpa:
    properties:
      hibernate:
        show_sql: true
        format_sql: true

Configuration

声明数据源

@Configuration
public class DataSourceConfigurer
{

    //用户数据源
    @Bean(name = "userDataSource")//装配该方法返回值为userDataSource管理bean
    @Qualifier("userDataSource")//spring装配bean唯一标识
    @ConfigurationProperties(prefix="spring.datasource.user")//application.yml文件内配置数据源的前缀
    public DataSource userDataSource(){return DataSourceBuilder.create().build();}

    //书籍数据源
    @Bean(name = "bookDataSource")
    @Primary//配置该数据源为主数据源
    @Qualifier("bookDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.book")
    public DataSource bookDataSource(){return DataSourceBuilder.create().build();}
}

@Primary
@Primary配置了数据源为主数据源，当没有配置自动切换的package时默认使用该数据源进行数据处理操作。

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef="entityManagerFactoryBook",//实体管理引用
        transactionManagerRef="transactionManagerBook",//事务管理引用
        basePackages = { "com.yuqiyu.chapter24.book"}) //设置书籍数据源所应用到的包
public class BookDataSourceConfigurer
{
    //注入书籍数据源
    @Autowired
    @Qualifier("bookDataSource")
    private DataSource bookDataSource;

    //配置EntityManager实体
    @Primary
    @Bean(name = "entityManagerBook")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactoryBook(builder).getObject().createEntityManager();
    }

    //配置EntityManager工厂实体
    @Primary
    @Bean(name = "entityManagerFactoryBook")
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryBook (EntityManagerFactoryBuilder builder) {
        return builder
                .dataSource(bookDataSource)
                .properties(getVendorProperties(bookDataSource))
                .packages(new String[]{ "com.yuqiyu.chapter24.book" }) //设置应用creditDataSource的基础包名
                .persistenceUnit("bookPersistenceUnit")
                .build();
    }

    //注入jpa配置实体
    @Autowired
    private JpaProperties jpaProperties;

    //获取jpa配置信息
    private Map<String, String> getVendorProperties(DataSource dataSource) {
        return jpaProperties.getHibernateProperties(dataSource);
    }

    //配置事务
    @Primary
    @Bean(name = "transactionManagerBook")
    public PlatformTransactionManager transactionManagerBook(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryBook(builder).getObject());
    }
}

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef="entityManagerFactoryUser",//实体管理引用
        transactionManagerRef="transactionManagerUser",//失误管理引用
        basePackages = { "com.yuqiyu.chapter24.user"}) //设置用户数据源所应用到的包
public class UserDataSourceConfigurer
{
    //注入用户数据源
    @Autowired
    @Qualifier("userDataSource")
    private DataSource userDataSource;

    //配置EntityManager实体
    @Bean(name = "entityManagerUser")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactoryUser(builder).getObject().createEntityManager();
    }

    //配置EntityManager工厂实体
    @Bean(name = "entityManagerFactoryUser")
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryUser (EntityManagerFactoryBuilder builder) {
        return builder
                .dataSource(userDataSource)
                .properties(getVendorProperties(userDataSource))
                .packages(new String[]{ "com.yuqiyu.chapter24.user" }) //设置应用creditDataSource的基础包名
                .persistenceUnit("userPersistenceUnit")
                .build();
    }

    //注入jpa配置实体
    @Autowired
    private JpaProperties jpaProperties;

    //获取jpa配置信息
    private Map<String, String> getVendorProperties(DataSource dataSource) {
        return jpaProperties.getHibernateProperties(dataSource);
    }

    //配置事务
    @Bean(name = "transactionManagerUser")
    public PlatformTransactionManager transactionManagerUser(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryUser(builder).getObject());
    }
}