一般情况下，SpringBoot中使用Hikari只需要在yaml文件中配置Hikari的数据源信息即可，例如
spring:
datasource:
url: jdbc:mysql://localhost:3306/test
username: foo
password: bar
hikari:
connection-timeout: 30000
minimum-idle: 5
maximum-pool-size: 12
idle-timeout: 300000
max-lifetime: 1200000
register-mbeans: true
不过，若是你需要手动创建数据源Bean，则很有可能会得到如下错误
org.springframework.jmx.export.UnableToRegisterMBeanException: Unable to register MBean [HikariDataSource (HikariDataSource)] with key 'dataSource'; nested exception is javax.management.InstanceAlreadyExistsException: MXBean already registered with name com.zaxxer.hikari:type=PoolConfig (HikariDataSource)
错误的原因是，Hikari数据源的创建方法里自带了注册MBean的操作，而SpringBoot在初始化时会搜索所有Bean，并将可能是MBean的Bean注册为MBean（判断方法参见org.springframework.jmx.support.JmxUtils#isMBean方法，大意是判断这个类是否继承自javax.management.DynamicMBean，或者该类继承/实现了以某个”MBean”和或”MXBean”结尾的类/接口），从而导致重复注册MBean的错误。
解决方法是，将这个手动创建的Bean放到org.springframework.jmx.export.MBeanExporter的排除列表里，如下所示：
@Configuration
public class BeansConfig {
@Resource
private HikariDataSourceConfig hikariDataSourceConfig;
@Resource
private ObjectProvider<MBeanExporter> mBeanExporter;
@Bean("dataSource")
public DataSource createDataSource() {
String url = hikariDataSourceConfig.getUrl();
String username = hikariDataSourceConfig.getUsername();
String password = hikariDataSourceConfig.getPassword();
long idleTimeoutInMilliSeconds =
hikariDataSourceConfig.getIdleTimeOutInMilliseconds();
long maxLifetimeInMilliseconds =
hikariDataSourceConfig.getMaxLifetimeInMilliseconds();
int maximumPoolSize = hikariDataSourceConfig.getMaximumPoolSize();
int minimumIdle = hikariDataSourceConfig.getMinimumIdle();
String poolName = "HikariDataSource";
HikariConfig hikariConfig = new HikariConfig();
hikariConfig.setRegisterMbeans(true);
hikariConfig.setJdbcUrl(url);
hikariConfig.setUsername(username);
hikariConfig.setPassword(password);
hikariConfig.setIdleTimeout(idleTimeoutInMilliSeconds);
hikariConfig.setMaxLifetime(maxLifetimeInMilliseconds);
hikariConfig.setMaximumPoolSize(maximumPoolSize);
hikariConfig.setMinimumIdle(minimumIdle);
hikariConfig.setPoolName(poolName);
HikariDataSource dataSource = new HikariDataSource(hikariConfig);
mBeanExporter
.ifUnique((exporter) -> exporter.addExcludedBean("dataSource"));
return dataSource;
}
}
这里指的注意的是，Bean的名字”dataSource”通过mBeanExporter.ifUnique((exporter) -> exporter.addExcludedBean("dataSource"));放入到排除列表里，这样就不会出现重复注册的问题了。