set empty property as null in config

src/main/java/com/zaxxer/hikari/HikariConfig.java

@@ -42,6 +42,8 @@ import com.codahale.metrics.health.HealthCheckRegistry;
 import com.zaxxer.hikari.metrics.MetricsTrackerFactory;
 import com.zaxxer.hikari.util.PropertyElf;
 
+import static com.zaxxer.hikari.util.UtilityElf.nullOrNotEmpty;
+
 public class HikariConfig implements HikariConfigMXBean
 {
    private static final Logger LOGGER = LoggerFactory.getLogger(HikariConfig.class);
@@ -746,6 +748,16 @@ public class HikariConfig implements HikariConfigMXBean
    {
       validateNumerics();
 
+      // treat empty property as null
+      catalog = nullOrNotEmpty(catalog);
+      connectionInitSql = nullOrNotEmpty(connectionInitSql);
+      connectionTestQuery = nullOrNotEmpty(connectionTestQuery);
+      transactionIsolationName = nullOrNotEmpty(transactionIsolationName);
+      dataSourceClassName = nullOrNotEmpty(dataSourceClassName);
+      dataSourceJndiName = nullOrNotEmpty(dataSourceJndiName);
+      driverClassName = nullOrNotEmpty(driverClassName);
+      jdbcUrl = nullOrNotEmpty(jdbcUrl);
+
       if (poolName == null) {
          poolName = "HikariPool-" + POOL_NUMBER.getAndIncrement();
       }

src/main/java/com/zaxxer/hikari/pool/PoolBase.java

@@ -6,7 +6,6 @@ import static com.zaxxer.hikari.pool.ProxyConnection.DIRTY_BIT_ISOLATION;
 import static com.zaxxer.hikari.pool.ProxyConnection.DIRTY_BIT_NETTIMEOUT;
 import static com.zaxxer.hikari.pool.ProxyConnection.DIRTY_BIT_READONLY;
 import static com.zaxxer.hikari.util.UtilityElf.createInstance;
-import static com.zaxxer.hikari.util.UtilityElf.nullOrNotEmpty;
 
 import java.lang.management.ManagementFactory;
 import java.sql.Connection;
@@ -68,14 +67,14 @@ abstract class PoolBase
       this.config = config;
 
       this.networkTimeout = -1;
-      this.catalog = nullOrNotEmpty(config.getCatalog());
+      this.catalog = config.getCatalog();
       this.isReadOnly = config.isReadOnly();
       this.isAutoCommit = config.isAutoCommit();
       this.transactionIsolation = UtilityElf.getTransactionIsolation(config.getTransactionIsolation());
 
       this.isQueryTimeoutSupported = UNINITIALIZED;
       this.isNetworkTimeoutSupported = UNINITIALIZED;
-      this.isUseJdbc4Validation = nullOrNotEmpty(config.getConnectionTestQuery()) == null;
+      this.isUseJdbc4Validation = config.getConnectionTestQuery() == null;
       this.isIsolateInternalQueries = config.isIsolateInternalQueries();
 
       this.poolName = config.getPoolName();

src/main/java/com/zaxxer/hikari/util/UtilityElf.java

@@ -124,14 +124,14 @@ public final class UtilityElf
     */
    public static int getTransactionIsolation(final String transactionIsolationName)
    {
-      if (nullOrNotEmpty(transactionIsolationName) != null) {
+      if (transactionIsolationName != null) {
          try {
-            final String upperName = transactionIsolationName.trim().toUpperCase();
+            final String upperName = transactionIsolationName.toUpperCase();
             if (upperName.startsWith("TRANSACTION_")) {
                Field field = Connection.class.getField(upperName);
                return field.getInt(null);
             }
-            final int level = Integer.parseInt(transactionIsolationName.trim());
+            final int level = Integer.parseInt(transactionIsolationName);
             switch (level) {
                case Connection.TRANSACTION_READ_UNCOMMITTED:
                case Connection.TRANSACTION_READ_COMMITTED: