Make HikariConfig able to retrieve passwords dynamically from a password supplier (#1196)

Adds a passwordSupplier property with setter and getter
Refactors the password property to use a built-in passwordSupplier
If setting the password directly, the passwordSupplier property returns NULL

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

@@ -39,6 +39,7 @@ import java.util.TreeSet;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.function.Supplier;
 
 import static com.zaxxer.hikari.util.UtilityElf.getNullIfEmpty;
 import static com.zaxxer.hikari.util.UtilityElf.safeIsAssignableFrom;
@@ -48,6 +49,19 @@ import static java.util.concurrent.TimeUnit.SECONDS;
 @SuppressWarnings({"SameParameterValue", "unused"})
 public class HikariConfig implements HikariConfigMXBean
 {
+   // Password supplier to use when the password is set directly to the configuration instance.
+   private static class StringPasswordSupplier implements Supplier<String> {
+      private final String password;
+
+      public StringPasswordSupplier(String password) {
+         this.password = password;
+      }
+
+      @Override public String get() {
+         return password;
+      }
+   }
+
    private static final Logger LOGGER = LoggerFactory.getLogger(HikariConfig.class);
 
    private static final char[] ID_CHARACTERS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
@@ -70,7 +84,7 @@ public class HikariConfig implements HikariConfigMXBean
    private volatile int maxPoolSize;
    private volatile int minIdle;
    private volatile String username;
-   private volatile String password;
+   private volatile Supplier<String> passwordSupplier = new StringPasswordSupplier(null);
 
    // Properties NOT changeable at runtime
    //
@@ -268,13 +282,34 @@ public class HikariConfig implements HikariConfigMXBean
       this.minIdle = minIdle;
    }
 
+   /**
+    * Get the password supplier to use to provide the password for DataSource.getConnection(user, password) calls.
+    * @return the password supplier or null if there is no supplier or the password has been set directly.
+    */
+   public Supplier<String> getPasswordSupplier()
+   {
+      return (passwordSupplier instanceof StringPasswordSupplier) ? null : passwordSupplier;
+   }
+
+   /**
+    * Set the password supplier to use for DataSource.getConnection(username, password) calls.
+    * @param passwordSupplier the password supplier
+    */
+   public void setPasswordSupplier(Supplier<String> passwordSupplier)
+   {
+      if (passwordSupplier == null) {
+         throw new IllegalArgumentException("passwordSupplier cannot be null");
+      }
+      this.passwordSupplier = passwordSupplier;
+   }
+
    /**
     * Get the default password to use for DataSource.getConnection(username, password) calls.
     * @return the password
     */
    public String getPassword()
    {
-      return password;
+      return passwordSupplier.get();
    }
 
    /**
@@ -284,7 +319,7 @@ public class HikariConfig implements HikariConfigMXBean
    @Override
    public void setPassword(String password)
    {
-      this.password = password;
+      setPasswordSupplier(new StringPasswordSupplier(password));
    }
 
    /**

src/test/java/com/zaxxer/hikari/TestHikariConfig.java

@@ -0,0 +1,56 @@
+/*
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.zaxxer.hikari;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.function.Supplier;
+
+public class TestHikariConfig {
+
+   @Test
+   public void testPasswordAsString()
+   {
+      // default password NULL
+      HikariConfig config = new HikariConfig();
+      Assert.assertNull(config.getPassword());
+      Assert.assertNull(config.getPasswordSupplier());
+
+      // set password NULL
+      config = new HikariConfig();
+      config.setPassword(null);
+      Assert.assertNull(config.getPassword());
+      Assert.assertNull(config.getPasswordSupplier());
+
+      // set password value
+      config = new HikariConfig();
+      config.setPassword("password");
+      Assert.assertEquals("password", config.getPassword());
+      Assert.assertNull(config.getPasswordSupplier());
+   }
+
+   @Test
+   public void testPasswordAsSupplier()
+   {
+      HikariConfig config = new HikariConfig();
+      Supplier<String> supplier = () -> "password";
+      config.setPasswordSupplier(supplier);
+      Assert.assertEquals("password", config.getPassword());
+      Assert.assertEquals(supplier, config.getPasswordSupplier());
+   }
+
+}