Add DataSourceVerifier to check DB connection on startup

New class `DataSourceVerifier` created to ensure that the database connection is successfully established when the application context is refreshed. It logs messages indicating the success or failure of this verification.

dictionaryweights/src/main/java/edu/harvard/dbmi/avillach/dictionaryweights/DataSourceVerifier.java

@@ -0,0 +1,39 @@
+package edu.harvard.dbmi.avillach.dictionary.datasource;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.event.ContextRefreshedEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Service;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+
+@Service
+public class DataSourceVerifier {
+
+    private static final Logger LOG = LoggerFactory.getLogger(DataSourceVerifier.class);
+
+    private final DataSource dataSource;
+
+    @Autowired
+    public DataSourceVerifier(DataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    @EventListener(ContextRefreshedEvent.class)
+    public void verifyDataSourceConnection() {
+        try (Connection connection = dataSource.getConnection()) {
+            if (connection != null) {
+                LOG.info("Datasource connection verified successfully.");
+            } else {
+                LOG.info("Failed to obtain a connection from the datasource.");
+            }
+        } catch (SQLException e) {
+            LOG.info("Error verifying datasource connection: {}", e.getMessage());
+        }
+    }
+
+}