Fixes #878 Searching for driverClass in both hikari class classloader and Thread Context ClassLoader (#902)

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

@@ -313,13 +313,32 @@ public class HikariConfig implements HikariConfigMXBean
 
    public void setDriverClassName(String driverClassName)
    {
+      Class<?> driverClass = null;
+      try {
+         driverClass = this.getClass().getClassLoader().loadClass(driverClassName);
+         LOGGER.debug("Driver class found in the HikariConfig class classloader {}", this.getClass().getClassLoader());
+      } catch (ClassNotFoundException e) {
+         ClassLoader threadContextClassLoader = Thread.currentThread().getContextClassLoader();
+         if (threadContextClassLoader != null && threadContextClassLoader != this.getClass().getClassLoader()) {
+            try {
+               driverClass = threadContextClassLoader.loadClass(driverClassName);
+               LOGGER.debug("Driver class found in Thread context class loader {}", threadContextClassLoader);
+            } catch (ClassNotFoundException e1) {
+               LOGGER.error("Failed to load class of driverClassName {} in either of HikariConfig class classloader {} or Thread context classloader {}", driverClassName, this.getClass().getClassLoader(), threadContextClassLoader);
+            }
+         } else {
+            LOGGER.error("Failed to load class of driverClassName {} in HikariConfig class classloader {}", driverClassName, this.getClass().getClassLoader());
+         }
+      }
+      if (driverClass == null) {
+         throw new RuntimeException("Failed to load class of driverClassName [" + driverClassName + "] in either of HikariConfig class loader or Thread context classloader");
+      }
       try {
-         Class<?> driverClass = this.getClass().getClassLoader().loadClass(driverClassName);
          driverClass.newInstance();
          this.driverClassName = driverClassName;
       }
       catch (Exception e) {
-         throw new RuntimeException("Failed to load class of driverClassName " + driverClassName, e);
+         throw new RuntimeException("Failed to instantiate class " + driverClassName, e);
       }
    }
 

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

@@ -66,12 +66,29 @@ public final class DriverDataSource implements DataSource
 
          if (driver == null) {
             LOGGER.warn("Registered driver with driverClassName={} was not found, trying direct instantiation.", driverClassName);
+            Class<?> driverClass = null;
             try {
-               Class<?> driverClass = this.getClass().getClassLoader().loadClass(driverClassName);
-               driver = (Driver) driverClass.newInstance();
+               driverClass = this.getClass().getClassLoader().loadClass(driverClassName);
+               LOGGER.debug("Driver class found in the HikariConfig class classloader {}", this.getClass().getClassLoader());
+            } catch (ClassNotFoundException e) {
+               ClassLoader threadContextClassLoader = Thread.currentThread().getContextClassLoader();
+               if (threadContextClassLoader != null && threadContextClassLoader != this.getClass().getClassLoader()) {
+                  try {
+                     driverClass = threadContextClassLoader.loadClass(driverClassName);
+                     LOGGER.debug("Driver class found in Thread context class loader {}", threadContextClassLoader);
+                  } catch (ClassNotFoundException e1) {
+                     LOGGER.warn("Failed to load class of driverClassName {} in either of HikariConfig class classloader {} or Thread context classloader {}", driverClassName, this.getClass().getClassLoader(), threadContextClassLoader);
+                  }
+               } else {
+                  LOGGER.warn("Failed to load class of driverClassName {} in HikariConfig class classloader {}", driverClassName, this.getClass().getClassLoader());
+               }
             }
-            catch (Exception e) {
-               LOGGER.warn("Failed to create instance of driver class {}, trying jdbcUrl resolution", driverClassName, e);
+            if (driverClass != null) {
+               try {
+                  driver = (Driver) driverClass.newInstance();
+               } catch (Exception e) {
+                  LOGGER.warn("Failed to create instance of driver class {}, trying jdbcUrl resolution", driverClassName, e);
+               }
             }
          }
       }