querying backbone

src/Main.java

@@ -1,6 +1,9 @@
+import data.enums.CustomReadPreparedStatements;
 import services.AppConfigService;
 import services.DatabaseService;
 
+import java.sql.ResultSet;
+
 public class Main {
     public static void main(String[] args) {
         final App app = new App();
@@ -18,6 +21,7 @@ class App {
     final AppConfigService appConfigService;
 
     public void run() {
-        appConfigService.promptUserArguments();
+        //appConfigService.promptUserArguments();
+        final ResultSet[] resultSetsQuery1 = databaseService.executeReadReportsEndpoint(CustomReadPreparedStatements.HighestAndLowest10Vaccination);
     }
 }

src/apis/DatabaseApi.java

@@ -0,0 +1,17 @@
+package apis;
+
+import data.dtos.QueryDTO;
+
+import java.sql.*;
+
+public class DatabaseApi {
+    public PreparedStatement performQuery(QueryDTO queryDTO, Connection connection) {
+        try {
+            PreparedStatement statement = connection.prepareStatement(queryDTO.queryTemplate().statementData);
+            statement.execute();
+            return statement;
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

src/data/constants/ConstFormatters.java

@@ -1,4 +1,4 @@
-package constants;
+package data.constants;
 
 import java.text.SimpleDateFormat;
 

src/data/constants/ConstValues.java

@@ -1,4 +1,4 @@
-package constants;
+package data.constants;
 
 public class ConstValues {
     //I

src/data/dtos/QueryDTO.java

@@ -0,0 +1,7 @@
+package data.dtos;
+
+import data.enums.CustomReadPreparedStatements;
+
+public record QueryDTO(CustomReadPreparedStatements queryTemplate, Object[] placeholderReplacements) {
+
+}

src/data/enums/CustomReadPreparedStatements.java

@@ -0,0 +1,34 @@
+package data.enums;
+
+public enum CustomReadPreparedStatements {
+    HighestAndLowest10Vaccination("""
+            WITH vacc_count_per_country AS (
+              SELECT iso_country, SUM(daily_vaccinations) as total_vaccinations
+              FROM vaccinations
+              GROUP BY iso_country
+            )
+            SELECT name, total_vaccinations
+            FROM countries JOIN vacc_count_per_country
+            ON countries.code = vacc_count_per_country.iso_country
+            ORDER BY total_vaccinations DESC
+            LIMIT 10;
+            
+            WITH vacc_count_per_country AS (
+              SELECT iso_country, SUM(daily_vaccinations) as total_vaccinations
+              FROM vaccinations
+              GROUP BY iso_country
+            )
+            SELECT name, total_vaccinations
+            FROM countries JOIN vacc_count_per_country
+            ON countries.code = vacc_count_per_country.iso_country
+            ORDER BY total_vaccinations ASC
+            LIMIT 10;
+            """
+    );
+
+    public final String statementData;
+
+    private CustomReadPreparedStatements(String statementData) {
+        this.statementData = statementData;
+    }
+}

src/services/AppConfigService.java

@@ -1,7 +1,7 @@
 package services;
 
-import constants.ConstFormatters;
-import constants.ConstValues;
+import data.constants.ConstFormatters;
+import data.constants.ConstValues;
 
 import java.text.ParseException;
 
@@ -38,7 +38,7 @@ public class AppConfigService {
                 System.out.printf("Unable to parse date. Should be in format '%s'.\nTry again:%n", ConstFormatters.APPLICATION_DATE_FORMATTER.toPattern());
             }
         }
-        
+
         scanner.close();
     }
 }

src/services/DatabaseService.java

@@ -1,8 +1,12 @@
 package services;
 
-import java.sql.Connection;
-import java.sql.DriverManager;
-import java.sql.SQLException;
+import apis.DatabaseApi;
+import data.dtos.QueryDTO;
+import data.enums.CustomReadPreparedStatements;
+
+import javax.xml.transform.Result;
+import java.sql.*;
+import java.util.ArrayList;
 
 /**
  * Stores the active connection between the app and the local SQL Server.
@@ -12,13 +16,31 @@ public class DatabaseService {
     private final String user = "postgres";
     private final String password = "postgres";
 
+    private final DatabaseApi databaseApi;
     private final Connection connection;
 
     public DatabaseService() {
         connection = connect();
+        databaseApi = new DatabaseApi();
     }
 
-    /**
+    public ResultSet[] executeReadReportsEndpoint(CustomReadPreparedStatements customPreparedStatement) {
+        final QueryDTO queryDTO = new QueryDTO(customPreparedStatement, new Object[]{});
+        final PreparedStatement resultStatement = databaseApi.performQuery(queryDTO, connection);
+        try {
+            final ArrayList<ResultSet> resultSets = new ArrayList<>();
+            do {
+                resultSets.add(resultStatement.getResultSet());
+            }
+            while (resultStatement.getMoreResults());
+
+            return resultSets.toArray(new ResultSet[0]);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+        /**
      * Connect to the PostgreSQL database
      *
      * @return a Connection object
@@ -34,4 +56,4 @@ public class DatabaseService {
 
         return  connection;
     }
-}
+}