Order

Spring-Boot-2.0.0-M1 version changed the default database connection pool from tomcat jdbc pool to hikari. here, the default configuration of hikari is mainly studied.

spring-configuration-metadata.json

spring-boot-autoconfigure-2.0.0.M7.jar! /META-INF/spring-configuration-metadata.json

      {
      "sourceType": "org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration$Hikari",
      "name": "spring.datasource.hikari",
      "sourceMethod": "dataSource(org.springframework.boot.autoconfigure.jdbc.DataSourceProperties)",
      "type": "com.zaxxer.hikari.HikariDataSource"
    },
      {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.allow-pool-suspension",
      "type": "java.lang.Boolean"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.auto-commit",
      "type": "java.lang.Boolean"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.catalog",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.connection-init-sql",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.connection-test-query",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.connection-timeout",
      "type": "java.lang.Long"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.data-source-class-name",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.data-source-j-n-d-i",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.data-source-properties",
      "type": "java.util.Properties"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.driver-class-name",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.health-check-properties",
      "type": "java.util.Properties"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.health-check-registry",
      "type": "java.lang.Object"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.idle-timeout",
      "type": "java.lang.Long"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "deprecated": true,
      "name": "spring.datasource.hikari.initialization-fail-fast", //initializationFailTimeout > 0
      "type": "java.lang.Boolean",
      "deprecation": {}
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.initialization-fail-timeout",
      "type": "java.lang.Long"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.isolate-internal-queries",
      "type": "java.lang.Boolean"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.jdbc-url",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "deprecated": true,
      "name": "spring.datasource.hikari.jdbc4-connection-test", //废弃
      "type": "java.lang.Boolean",
      "deprecation": {}
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.leak-detection-threshold",
      "type": "java.lang.Long"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.login-timeout", //在HikariDataSource及PoolBase中
      "type": "java.lang.Integer"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.max-lifetime",
      "type": "java.lang.Long"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.maximum-pool-size",
      "type": "java.lang.Integer"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.metric-registry",
      "type": "java.lang.Object"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.metrics-tracker-factory",
      "type": "com.zaxxer.hikari.metrics.MetricsTrackerFactory"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.minimum-idle",
      "type": "java.lang.Integer"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.password",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.pool-name",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.read-only",
      "type": "java.lang.Boolean"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.register-mbeans",
      "type": "java.lang.Boolean"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.scheduled-executor",
      "type": "java.util.concurrent.ScheduledExecutorService"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "deprecated": true,
      "name": "spring.datasource.hikari.scheduled-executor-service",
      "type": "java.util.concurrent.ScheduledThreadPoolExecutor",
      "deprecation": {}
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.schema",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.transaction-isolation", //transactionIsolationName
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.username",
      "type": "java.lang.String"
    },
    {
      "sourceType": "com.zaxxer.hikari.HikariDataSource",
      "name": "spring.datasource.hikari.validation-timeout",
      "type": "java.lang.Long"
    },

HikariConfig

HikariCP-2.7.6-sources.jar! /com/zaxxer/hikari/HikariConfig.java

@SuppressWarnings({"SameParameterValue", "unused"})
public class HikariConfig implements HikariConfigMXBean
{
   private static final Logger LOGGER = LoggerFactory.getLogger(HikariConfig.class);

   private static final char[] ID_CHARACTERS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
   private static final long CONNECTION_TIMEOUT = SECONDS.toMillis(30);
   private static final long VALIDATION_TIMEOUT = SECONDS.toMillis(5);
   private static final long IDLE_TIMEOUT = MINUTES.toMillis(10);
   private static final long MAX_LIFETIME = MINUTES.toMillis(30);
   private static final int DEFAULT_POOL_SIZE = 10;
   //......

   /**
    * Default constructor
    */
   public HikariConfig()
   {
      dataSourceProperties = new Properties();
      healthCheckProperties = new Properties();

      minIdle = -1;
      maxPoolSize = -1;
      maxLifetime = MAX_LIFETIME;
      connectionTimeout = CONNECTION_TIMEOUT;
      validationTimeout = VALIDATION_TIMEOUT;
      idleTimeout = IDLE_TIMEOUT;
      initializationFailTimeout = 1;
      isAutoCommit = true;

      String systemProp = System.getProperty("hikaricp.configurationFile");
      if (systemProp != null) {
         loadProperties(systemProp);
      }
   }

   @Override
   public void setConnectionTimeout(long connectionTimeoutMs)
   {
      if (sealed) throw new IllegalStateException("The configuration of the pool is sealed once started.  Use HikariConfigMXBean for runtime changes.");

      if (connectionTimeoutMs == 0) {
         this.connectionTimeout = Integer.MAX_VALUE;
      }
      else if (connectionTimeoutMs < 250) {
         throw new IllegalArgumentException("connectionTimeout cannot be less than 250ms");
      }
      else {
         this.connectionTimeout = connectionTimeoutMs;
      }
   }

   @Override
   public void setIdleTimeout(long idleTimeoutMs)
   {
      if (sealed) throw new IllegalStateException("The configuration of the pool is sealed once started.  Use HikariConfigMXBean for runtime changes.");

      if (idleTimeoutMs < 0) {
         throw new IllegalArgumentException("idleTimeout cannot be negative");
      }
      this.idleTimeout = idleTimeoutMs;
   }

   @Override
   public void setMaximumPoolSize(int maxPoolSize)
   {
      if (sealed) throw new IllegalStateException("The configuration of the pool is sealed once started.  Use HikariConfigMXBean for runtime changes.");

      if (maxPoolSize < 1) {
         throw new IllegalArgumentException("maxPoolSize cannot be less than 1");
      }
      this.maxPoolSize = maxPoolSize;
   }

   @Override
   public void setMinimumIdle(int minIdle)
   {
      if (sealed) throw new IllegalStateException("The configuration of the pool is sealed once started.  Use HikariConfigMXBean for runtime changes.");

      if (minIdle < 0) {
         throw new IllegalArgumentException("minimumIdle cannot be negative");
      }
      this.minIdle = minIdle;
   }

   @Override
   public void setValidationTimeout(long validationTimeoutMs)
   {
      if (sealed) throw new IllegalStateException("The configuration of the pool is sealed once started.  Use HikariConfigMXBean for runtime changes.");

      if (validationTimeoutMs < 250) {
         throw new IllegalArgumentException("validationTimeout cannot be less than 250ms");
      }

      this.validationTimeout = validationTimeoutMs;
   }

   public void validate()
   {
      if (poolName == null) {
         poolName = generatePoolName();
      }
      else if (isRegisterMbeans && poolName.contains(":")) {
         throw new IllegalArgumentException("poolName cannot contain ':' when used with JMX");
      }

      // treat empty property as null
      catalog = getNullIfEmpty(catalog);
      connectionInitSql = getNullIfEmpty(connectionInitSql);
      connectionTestQuery = getNullIfEmpty(connectionTestQuery);
      transactionIsolationName = getNullIfEmpty(transactionIsolationName);
      dataSourceClassName = getNullIfEmpty(dataSourceClassName);
      dataSourceJndiName = getNullIfEmpty(dataSourceJndiName);
      driverClassName = getNullIfEmpty(driverClassName);
      jdbcUrl = getNullIfEmpty(jdbcUrl);

      // Check Data Source Options
      if (dataSource != null) {
         if (dataSourceClassName != null) {
            LOGGER.warn("{} - using dataSource and ignoring dataSourceClassName.", poolName);
         }
      }
      else if (dataSourceClassName != null) {
         if (driverClassName != null) {
            LOGGER.error("{} - cannot use driverClassName and dataSourceClassName together.", poolName);
            // NOTE: This exception text is referenced by a Spring Boot FailureAnalyzer, it should not be
            // changed without first notifying the Spring Boot developers.
            throw new IllegalStateException("cannot use driverClassName and dataSourceClassName together.");
         }
         else if (jdbcUrl != null) {
            LOGGER.warn("{} - using dataSourceClassName and ignoring jdbcUrl.", poolName);
         }
      }
      else if (jdbcUrl != null || dataSourceJndiName != null) {
         // ok
      }
      else if (driverClassName != null) {
         LOGGER.error("{} - jdbcUrl is required with driverClassName.", poolName);
         throw new IllegalArgumentException("jdbcUrl is required with driverClassName.");
      }
      else {
         LOGGER.error("{} - dataSource or dataSourceClassName or jdbcUrl is required.", poolName);
         throw new IllegalArgumentException("dataSource or dataSourceClassName or jdbcUrl is required.");
      }

      validateNumerics();

      if (LOGGER.isDebugEnabled() || unitTest) {
         logConfiguration();
      }
   }

   private void validateNumerics()
   {
      if (maxLifetime != 0 && maxLifetime < SECONDS.toMillis(30)) {
         LOGGER.warn("{} - maxLifetime is less than 30000ms, setting to default {}ms.", poolName, MAX_LIFETIME);
         maxLifetime = MAX_LIFETIME;
      }

      if (idleTimeout + SECONDS.toMillis(1) > maxLifetime && maxLifetime > 0) {
         LOGGER.warn("{} - idleTimeout is close to or more than maxLifetime, disabling it.", poolName);
         idleTimeout = 0;
      }

      if (idleTimeout != 0 && idleTimeout < SECONDS.toMillis(10)) {
         LOGGER.warn("{} - idleTimeout is less than 10000ms, setting to default {}ms.", poolName, IDLE_TIMEOUT);
         idleTimeout = IDLE_TIMEOUT;
      }

      if (leakDetectionThreshold > 0 && !unitTest) {
         if (leakDetectionThreshold < SECONDS.toMillis(2) || (leakDetectionThreshold > maxLifetime && maxLifetime > 0)) {
            LOGGER.warn("{} - leakDetectionThreshold is less than 2000ms or more than maxLifetime, disabling it.", poolName);
            leakDetectionThreshold = 0;
         }
      }

      if (connectionTimeout < 250) {
         LOGGER.warn("{} - connectionTimeout is less than 250ms, setting to {}ms.", poolName, CONNECTION_TIMEOUT);
         connectionTimeout = CONNECTION_TIMEOUT;
      }

      if (validationTimeout < 250) {
         LOGGER.warn("{} - validationTimeout is less than 250ms, setting to {}ms.", poolName, VALIDATION_TIMEOUT);
         validationTimeout = VALIDATION_TIMEOUT;
      }

      if (maxPoolSize < 1) {
         maxPoolSize = (minIdle <= 0) ? DEFAULT_POOL_SIZE : minIdle;
      }

      if (minIdle < 0 || minIdle > maxPoolSize) {
         minIdle = maxPoolSize;
      }
   }
}   

You can see that parameter verification is added to the set method, and the validate method is also called in the configuration constructor and getConnection method.

   public HikariDataSource(HikariConfig configuration)
   {
      configuration.validate();
      configuration.copyStateTo(this);
      this.seal();

      LOGGER.info("{} - Starting...", configuration.getPoolName());
      pool = fastPathPool = new HikariPool(this);
      LOGGER.info("{} - Start completed.", configuration.getPoolName());
   }

   /** {@inheritDoc} */
   @Override
   public Connection getConnection() throws SQLException
   {
      if (isClosed()) {
         throw new SQLException("HikariDataSource " + this + " has been closed.");
      }

      if (fastPathPool != null) {
         return fastPathPool.getConnection();
      }

      // See http://en.wikipedia.org/wiki/Double-checked_locking#Usage_in_Java
      HikariPool result = pool;
      if (result == null) {
         synchronized (this) {
            result = pool;
            if (result == null) {
               validate();
               LOGGER.info("{} - Starting...", getPoolName());
               try {
                  pool = result = new HikariPool(this);
                  this.seal();
               }
               catch (PoolInitializationException pie) {
                  if (pie.getCause() instanceof SQLException) {
                     throw (SQLException) pie.getCause();
                  }
                  else {
                     throw pie;
                  }
               }
               LOGGER.info("{} - Start completed.", getPoolName());
            }
         }
      }

      return result.getConnection();
   }

Springboot’s autoconfig initializes HikariDataSource with reflection from BeanUtils and takes the default constructor, so the verification depends on the set method and the subsequent getConnection method.

PoolBase.setLoginTimeout

HikariCP-2.7.6-sources.jar! /com/zaxxer/hikari/pool/PoolBase.java

   /**
    * Set the loginTimeout on the specified DataSource.
    *
    * @param dataSource the DataSource
    */
   private void setLoginTimeout(final DataSource dataSource)
   {
      if (connectionTimeout != Integer.MAX_VALUE) {
         try {
            dataSource.setLoginTimeout(Math.max(1, (int) MILLISECONDS.toSeconds(500L + connectionTimeout)));
         }
         catch (Throwable e) {
            LOGGER.info("{} - Failed to set login timeout for data source. ({})", poolName, e.getMessage());
         }
      }
   }

This is initialized with loginTimeout, and the initial value is Math.max (1) (int) Milliseconds.to seconds (500L+Connectiontimeout))

Summary

The default values for the default configuration of springboot’s HikariDataSource are as follows

doc

• Spring-Boot-2.0.0-M1-Release-Notes