Master Druid: Configure, Monitor, and Optimize Spring Boot Data Sources

1. Basic Concepts

Druid is Alibaba's open‑source Java database connection pool designed for monitoring and extensibility. It offers richer monitoring features than HikariCP, which is slightly faster but less feature‑rich.

Druid provides built‑in filters such as StatFilter for statistics, WallFilter for SQL injection protection, and Log4j2 for logging.

2. Adding Maven Dependencies

<!-- Alibaba Druid starter -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.1.23</version>
</dependency>

<!-- MySQL driver -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

<!-- Log4j2 for SQL logging -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

<!-- Exclude default HikariCP when using MyBatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.3</version>
    <exclusions>
        <exclusion>
            <groupId>com.zaxxer</groupId>
            <artifactId>HikariCP</artifactId>
        </exclusion>
    </exclusions>
</dependency>

3. Configuring Druid Properties

All Druid settings can be placed in application.yml. Key sections include JDBC basics, pool size, timeout, validation query, prepared‑statement caching, and filter activation.

spring:
  datasource:
    username: xxx
    password: xxx
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?serverTimezone=Asia/Shanghai
    platform: mysql
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      initial-size: 5
      minIdle: 10
      max-active: 20
      max-wait: 60000
      time-between-eviction-runs-millis: 2000
      min-evictable-idle-time-millis: 600000
      max-evictable-idle-time-millis: 900000
      validationQuery: select 1
      testWhileIdle: true
      testOnBorrow: false
      testOnReturn: false
      poolPreparedStatements: true
      maxOpenPreparedStatements: 20
      keepAlive: true
      aop-patterns: "com.springboot.template.dao.*"
      filters: stat,wall,log4j2
      filter:
        stat:
          enabled: true
          db-type: mysql
          log-slow-sql: true
          slow-sql-millis: 2000
      web-stat-filter:
        enabled: true
        url-pattern: "/*"
        exclusions: "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*"
        session-stat-enable: true
        session-stat-max-count: 1000
      stat-view-servlet:
        enabled: true
        url-pattern: /druid/*
        reset-enable: false
        login-username: root
        login-password: 123
        allow: 127.0.0.1

These properties map to

com.alibaba.druid.spring.boot.autoconfigure.properties.DruidStatProperties

and

org.springframework.boot.autoconfigure.jdbc.DataSourceProperties

.

3.1 Configuring Filters

Filters can be enabled via spring.datasource.druid.filters or configured individually, e.g.:

# StatFilter
spring.datasource.druid.filter.stat.enabled=true
spring.datasource.druid.filter.stat.db-type=h2
spring.datasource.druid.filter.stat.log-slow-sql=true
spring.datasource.druid.filter.stat.slow-sql-millis=2000

# WallFilter
spring.datasource.druid.filter.wall.enabled=true
spring.datasource.druid.filter.wall.db-type=h2
spring.datasource.druid.filter.wall.config.delete-allow=false
spring.datasource.druid.filter.wall.config.drop-table-allow=false

4. SQL Monitoring

The WebStatFilter collects web‑related SQL statistics such as execution time, request count, and accessed tables.

spring:
  datasource:
    druid:
      web-stat-filter:
        enabled: true
        url-pattern: "/*"
        exclusions: "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*"
        session-stat-enable: true
        session-stat-max-count: 1000

5. Slow SQL Recording

Enable slow‑SQL logging by configuring the StatFilter:

spring:
  datasource:
    druid:
      filter:
        stat:
          enabled: true
          db-type: mysql
          log-slow-sql: true
          slow-sql-millis: 2000

SQL statements exceeding 2 seconds are logged.

6. Spring AOP Monitoring

Include the AOP starter and set the pointcut pattern to monitor DAO methods:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>

spring.datasource.druid.aop-patterns="com.springboot.template.dao.*"

7. Removing Druid Footer Ads

Two approaches are provided:

Manually comment out the // this.buildFooter(); line in common.js inside the Druid JAR.

Register a custom filter that intercepts the common.js request and strips the ad HTML via regular expressions.

Both methods work, but editing the JAR source is the most straightforward.

8. Accessing Druid Statistics Programmatically

After enabling StatFilter, you can retrieve monitoring data via DruidStatManagerFacade:

@RestController
@RequestMapping("/druid")
public class DruidStatController {
    @GetMapping("/stat")
    public Object druidStat() {
        return DruidStatManagerFacade.getInstance().getDataSourceStatDataList();
    }
}

The facade also offers other methods for detailed metrics.

The article concludes with a reminder that the configuration shown works for MySQL; adjust db-type for other databases.