记录下spring boot关于数据库连接池的一个小坑

环境：spring boot 1.5、JDK1.8

application.properties配置

# 驱动配置信息
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/mealsystem?useUnicode=true&characterEncoding=utf-8
spring.datasource.username = root
spring.datasource.password = 123456
spring.datasource.driverClassName = com.mysql.jdbc.Driver

#连接池的配置信息
spring.datasource.initialSize=5
spring.datasource.minIdle=5
spring.datasource.maxActive=20
spring.datasource.maxWait=60000
spring.datasource.timeBetweenEvictionRunsMillis=60000
spring.datasource.minEvictableIdleTimeMillis=300000
spring.datasource.validationQuery=SELECT 1 FROM DUAL
spring.datasource.testWhileIdle=true
spring.datasource.testOnBorrow=false
spring.datasource.testOnReturn=false
spring.datasource.poolPreparedStatements=true
spring.datasource.maxPoolPreparedStatementPerConnectionSize=20
spring.datasource.filters=stat,wall,log4j
spring.datasource.connectionProperties=druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000

先找到这个类：
org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder
并在下面的源码中打个断点

public DataSource build() {
        Classextends DataSource> type = this.getType();
        DataSource result = (DataSource)BeanUtils.instantiate(type);
        this.maybeGetDriverClassName();
        this.bind(result);
        return result;
    }

启动项目

我们可以发现，在没有配置spring.datasource.type时，spring boot默认的连接池是tomcat-jdbc
也就是说我们在application.properties中配置的连接池参数是无效的。
好，那我们再配置下这个属性，使用阿里巴巴的druid

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource

再启动下

再来看看1.5版本org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder的源码

private static final String[] DATA_SOURCE_TYPE_NAMES = new String[] {
            "org.apache.tomcat.jdbc.pool.DataSource",
            "com.zaxxer.hikari.HikariDataSource",
            "org.apache.commons.dbcp.BasicDataSource", // deprecated
            "org.apache.commons.dbcp2.BasicDataSource" };

spring boot 1.5的版本默认连接池为tomcat-jdbc
spring boot 2.0的版本默认连接池为HikariCP