1.引入druid连接池

<!-- Druid -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.0.28</version>
</dependency>

2.配置文件中：（我这里是ssm的配置）

<!-- 配置数据源ORACLE 数据库 -->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="driverClassName" value="${jdbc.driverClassName}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <!-- 初始化连接大小 -->
        <property name="initialSize" value="${jdbc.initialSize}"/>
        <!-- 连接池最大数量 -->
        <property name="maxActive" value="${jdbc.maxActive}"/>
        <!-- 连接池最小空闲 -->
        <property name="minIdle" value="${jdbc.minIdle}"/>
        <!-- 获取连接最大等待时间 -->
        <property name="maxWait" value="${jdbc.maxWait}"/>
        <!-- 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒 -->
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>
        <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
        <property name="minEvictableIdleTimeMillis" value="300000"/>
        <!-- 用来检测连接是否有效的sql，要求是一个查询语句-->
        <property name="validationQuery" value="select 'x' FROM DUAL"/>
        <!-- 申请连接时执行validationQuery检测连接是否有效，配置为true会降低性能 -->
        <property name="testWhileIdle" value="true"/>
        <property name="testOnBorrow" value="false"/>
        <!-- 归还连接时执行validationQuery检测连接是否有效，配置为true会降低性能  -->
        <property name="testOnReturn" value="false"/>
        <!-- 打开PSCache，并且指定每个连接上PSCache的大小 -->
        <property name="poolPreparedStatements" value="true"/>
        <property name="maxPoolPreparedStatementPerConnectionSize" value="20"/>
        <!--配置监控统计拦截的filters，属性类型是字符串，通过别名的方式配置扩展插件，常用的插件有：监控统计用的filter:stat；日志用的filter:log4j；防御SQL注入的filter:wall -->
        <property name="filters" value="stat,wall,slf4j"/>
        <!-- 通过connectProperties属性来打开mergeSql功能；慢SQL记录-->
         <property name="connectionProperties" value="druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000" />
        <!-- 关闭abanded连接时输出错误日志 -->
        <property name="logAbandoned" value="true"/>
    </bean>

3.web.xml配置：

<!-- 添加druid监控-->
    <servlet>
        <servlet-name>DruidStatView</servlet-name>
        <servlet-class>com.alibaba.druid.support.http.StatViewServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>DruidStatView</servlet-name>
        <url-pattern>/druid/*</url-pattern>
    </servlet-mapping>
    <!-- 添加Web应用等监控 -->
    <filter>
        <filter-name>DruidWebStatFilter</filter-name>
        <filter-class>com.alibaba.druid.support.http.WebStatFilter</filter-class>
        <init-param>
            <param-name>exclusions</param-name>
            <param-value>*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*</param-value>
        </init-param>
        <init-param>
            <param-name>profileEnable</param-name>
            <param-value>true</param-value>
        </init-param>
        <init-param>
            <param-name>principalCookieName</param-name>
            <param-value>USER_COOKIE</param-value>
        </init-param>
        <init-param>
            <param-name>principalSessionName</param-name>
            <param-value>USER_SESSION</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>DruidWebStatFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

访问地址：localhost/项目名/druid

spring boot 配置：
1.yml配置：

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driverClassName: com.mysql.jdbc.Driver
    url: xxx
    username: xx
    password: xx
    initialSize: 10
    minIdle: 10
    maxActive: 200
    # 配置获取连接等待超时的时间
    maxWait: 60000
    # 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒
    timeBetweenEvictionRunsMillis: 60000
    # 配置一个连接在池中最小生存的时间，单位是毫秒
    minEvictableIdleTimeMillis: 30000
    validationQuery: select 'x'
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    # 打开PSCache，并且指定每个连接上PSCache的大小
    poolPreparedStatements: true
    maxPoolPreparedStatementPerConnectionSize: 20
    # 配置监控统计拦截的filters
    filters: stat,wall,slf4j
    # 通过connectProperties属性来打开mergeSql功能；慢SQL记录
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000

2.spring boot大多于基于注解的配置，如果是web.xml配置，按上面的配置：

import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.support.http.StatViewServlet;
import com.alibaba.druid.support.http.WebStatFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;
import java.sql.SQLException;

/**
 * druid数据源状态监控
 *
 * @author huyw
 * @date 2018/11/12
 */
@Configuration
public class DruidDBConfig {
    private Logger logger = LoggerFactory.getLogger(DruidDBConfig.class);

    @Value("${spring.datasource.url}")
    private String dbUrl;

    @Value("${spring.datasource.username}")
    private String username;

    @Value("${spring.datasource.password}")
    private String password;

    @Value("${spring.datasource.driver-class-name}")
    private String driverClassName;

    @Value("${spring.datasource.initialSize}")
    private int initialSize;

    @Value("${spring.datasource.minIdle}")
    private int minIdle;

    @Value("${spring.datasource.maxActive}")
    private int maxActive;

    @Value("${spring.datasource.maxWait}")
    private int maxWait;

    @Value("${spring.datasource.timeBetweenEvictionRunsMillis}")
    private int timeBetweenEvictionRunsMillis;

    @Value("${spring.datasource.minEvictableIdleTimeMillis}")
    private int minEvictableIdleTimeMillis;

    @Value("${spring.datasource.validationQuery}")
    private String validationQuery;

    @Value("${spring.datasource.testWhileIdle}")
    private boolean testWhileIdle;

    @Value("${spring.datasource.testOnBorrow}")
    private boolean testOnBorrow;

    @Value("${spring.datasource.testOnReturn}")
    private boolean testOnReturn;

    @Value("${spring.datasource.poolPreparedStatements}")
    private boolean poolPreparedStatements;

    @Value("${spring.datasource.maxPoolPreparedStatementPerConnectionSize}")
    private int maxPoolPreparedStatementPerConnectionSize;

    @Value("${spring.datasource.filters}")
    private String filters;

    @Value("{spring.datasource.connectionProperties}")
    private String connectionProperties;

    @Bean(initMethod = "init", destroyMethod = "close") //声明其为Bean实例
    @Primary //在同样的DataSource中，首先使用被标注的DataSource
    public DataSource dataSource() {

        DruidDataSource datasource = new DruidDataSource();

        datasource.setUrl(dbUrl);
        datasource.setUsername(username);
        datasource.setPassword(password);
        datasource.setDriverClassName(driverClassName);
        //configuration
        datasource.setInitialSize(initialSize);
        datasource.setMinIdle(minIdle);
        datasource.setMaxActive(maxActive);
        datasource.setMaxWait(maxWait);
        datasource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
        datasource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
        datasource.setValidationQuery(validationQuery);
        datasource.setTestWhileIdle(testWhileIdle);
        datasource.setTestOnBorrow(testOnBorrow);
        datasource.setTestOnReturn(testOnReturn);
        datasource.setPoolPreparedStatements(poolPreparedStatements);
        datasource.setMaxPoolPreparedStatementPerConnectionSize(maxPoolPreparedStatementPerConnectionSize);
        try {
            datasource.setFilters(filters);
        } catch (SQLException e) {
            logger.error("druid configuration initialization filter", e);
        }
        datasource.setConnectionProperties(connectionProperties);

        return datasource;
    }

    /**
     * 注册一个StatViewServlet
     *
     * @return
     */
    @Bean
    public ServletRegistrationBean druidServlet() {
        ServletRegistrationBean reg = new ServletRegistrationBean();
        reg.setServlet(new StatViewServlet());
        reg.addUrlMappings(new String[]{"/druid/*"});
        //IP白名单 (没有配置或者为空，则允许所有访问)
        reg.addInitParameter("allow", "");
        //是否能够重置数据
        reg.addInitParameter("resetEnable", "false");
        //设置账号密码
        reg.addInitParameter("loginUsername", "admin");
        reg.addInitParameter("loginPassword", "123456");
        return reg;
    }

    /**
     * 注册一个：filterRegistrationBean
     *
     * @return
     */
    @Bean
    public FilterRegistrationBean filterRegistrationBean() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(new WebStatFilter());
        //添加过滤规则
        filterRegistrationBean.addUrlPatterns(new String[]{"/*"});
        //添加不需要忽略的格式信息
        filterRegistrationBean.addInitParameter("exclusions", "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
        filterRegistrationBean.addInitParameter("profileEnable", "true");
        filterRegistrationBean.addInitParameter("principalCookieName", "USER_COOKIE");
        filterRegistrationBean.addInitParameter("principalSessionName", "USER_SESSION");
        filterRegistrationBean.addInitParameter("DruidWebStatFilter", "/*");
        return filterRegistrationBean;
    }
}