目前Spring Boot中預設支援的連線池有dbcp,dbcp2, tomcat, hikari三種連線池。 

在springboot1.5之前預設tomcat連線池， 版本org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder的原始碼

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 2.0的版本預設連線池為HikariCP；

接著我們配置 application.properties

# 驅動配置資訊
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

#連線池的配置資訊
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
 
 

至此，小夥伴們以為配置已經完成了，但是當我們配置完這些發現並沒有生效。可以通過show processlist 檢視mysql 初始化連線上，發現並不是我們想要的連線數，

，最後 通過重寫datasource方法 
資料庫連線可以使用DataSource池進行自動配置。

import rt org.apache.tomcat.jdbc.pool.DataSource;
ie;
import rt org.springframework.boot.context.properties.ConfigurationtionProperties;
import rt org.springframework.context.annotation.Bean;
im;
import rt org.springframework.context.annotation.Configurationtion;
import rt org.springframework.context.annotation.PropertySourcource;


@Configuration
@ConfigurationProperties(prefix = "= "spring.datasource")
e")
public class DataSourceConfig {

    private String url;
    private String username;
    private String password;
    private int maxTotal;
    private int minIdle;
    private int maxIdle;
    private int initialSize;
    private String logAbandoned;
    private String removeAbandoned;
    private String removeAbandonedTimeout;
    private String maxWaitMillis;
    private String timeBetweenEvictionRunsMillis;
    private String numTestsPerEvictionRun;
    private String minEvictableIdleTimeMillis;




    @Bean
    public DataSource getDataSource() {
        DataSource  dataSource = new DataSource();
           dataSource.setDriverClasClassName("com.mysql.jdbc.Driver");
");
           dataSource.setUrl(url(url);
           dataSource.setUsername(ume(username);
           dataSource.setPassword(prd(password);
           dataSource.setMaxActive(ive(maxTotal);
           dataSource.setMinIdle(mie(minIdle);
           dataSource.setMaxIdle(mae(maxIdle);
           dataSource.setInitialSizlSize(initialSize);
        return dataSource;
    }

  //getset方法省略

}
 

在經過測試 ，發現mysql連結確實增加了，纏繞幾天的問題終於解決了，豁然開朗