[BAEL-3634] Code for Spark DataFrame article (#12039)

* [BAEL-3634] Code for Spark DataFrame article

* [BAEL-3634] Improve example data sample and sort aggregations

* [BAEL-3634] change column name for clarity

* [BAEL-3634] Update method name with  U.S english standard

Co-authored-by: uzma khan <uzma.khan@nominet.uk>

apache-spark/src/test/java/com/baeldung/dataframes/CustomerDataAggregationPipelineLiveTest.java

@@ -0,0 +1,52 @@
+package com.baeldung.dataframes;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Properties;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+class CustomerDataAggregationPipelineLiveTest {
+
+    private static Connection conn;
+
+    @BeforeAll
+    static void beforeAll() throws SQLException {
+        DriverManager.registerDriver(new org.postgresql.Driver());
+        String dbURL1 = "jdbc:postgresql://localhost:5432/customerdb";
+        conn = DriverManager.getConnection(dbURL1, "postgres", "postgres");
+
+        String sql = "drop table if exists customer";
+
+        PreparedStatement statement = conn.prepareStatement(sql);
+        statement.executeUpdate();
+    }
+
+    @Test
+    void givenCSVAndJSON_whenRun_thenStoresAggregatedDataFrameInDB() throws Exception {
+        Properties dbProps = new Properties();
+        dbProps.setProperty("connectionURL", "jdbc:postgresql://localhost:5432/customerdb");
+        dbProps.setProperty("driver", "org.postgresql.Driver");
+        dbProps.setProperty("user", "postgres");
+        dbProps.setProperty("password", "postgres");
+
+        CustomerDataAggregationPipeline pipeline = new CustomerDataAggregationPipeline(dbProps);
+        pipeline.run();
+
+        String allCustomersSql = "Select count(*) from customer";
+
+        Statement statement = conn.createStatement();
+        ResultSet resultSet = statement.executeQuery(allCustomersSql);
+        resultSet.next();
+        int count = resultSet.getInt(1);
+        assertEquals(7, count);
+    }
+
+}

apache-spark/src/test/java/com/baeldung/dataframes/CustomerToDataFrameConverterAppUnitTest.java

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+package com.baeldung.dataframes;
+
+import static com.baeldung.dataframes.CustomerToDataFrameConverterApp.convertAfterMappingRows;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Row;
+import org.junit.jupiter.api.Test;
+
+class CustomerToDataFrameConverterAppUnitTest {
+
+    @Test
+    void givenCustomers_whenConvertAfterMappingRows_thenConvertsToDataSet() {
+
+       List<Customer> customers = Arrays.asList(
+            new Customer("01", "jo", "Female", 2000),
+            new Customer("02", "jack", "Male", 1200)
+       );
+
+        Dataset<Row> customerDF = convertAfterMappingRows(customers);
+        List<Row> rows = customerDF.collectAsList();
+        Row row1 = rows.get(0);
+        Row row2 = rows.get(1);
+
+        assertEquals("01", row1.get(0));
+        assertEquals( "JO", row1.get(1));
+        assertEquals( "F", row1.get(2));
+        assertEquals( 2000, row1.get(3));
+
+        assertEquals("02", row2.get(0));
+        assertEquals( "JACK", row2.get(1));
+        assertEquals( "M", row2.get(2));
+        assertEquals( 1200, row2.get(3));
+    }
+
+    @Test
+    void givenCustomers_whenConvertWithNoChange_thenConvertsToDataSet() {
+
+        List<Customer> customers = Arrays.asList(
+            new Customer("01", "jo", "Female", 2000),
+            new Customer("02", "jack", "Male", 1200)
+        );
+
+        Dataset<Row> customerDF = CustomerToDataFrameConverterApp.convertToDataFrameWithNoChange();
+        List<Row> rows = customerDF.collectAsList();
+        Row row1 = rows.get(0);
+        Row row2 = rows.get(1);
+
+        assertEquals("01", row1.getAs("id"));
+        assertEquals( "jo", row1.getAs("name"));
+        assertEquals( "Female", row1.getAs("gender"));
+        assertEquals( 2000, (int)row1.getAs("transaction_amount"));
+
+        assertEquals("02", row2.getAs("id"));
+        assertEquals( "jack", row2.getAs("name"));
+        assertEquals( "Male", row2.getAs("gender"));
+        assertEquals( 1200, (int)row2.getAs("transaction_amount"));
+    }
+}