Merge pull request #15089 from niket17590/feature/BAEL-7086-ResultSetToMap

BAEL-7086 - Convert ResultSet Into Map

persistence-modules/core-java-persistence-3/pom.xml

@@ -0,0 +1,29 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung.core-java-persistence-3</groupId>
+    <artifactId>core-java-persistence-3</artifactId>
+    <name>core-java-persistence-3</name>
+    <version>0.1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>persistence-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <dependencies>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>${h2.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-dbutils</groupId>
+            <artifactId>commons-dbutils</artifactId>
+            <version>${commons-dbutils.version}</version>
+        </dependency>
+    </dependencies>
+    <properties>
+        <h2.version>2.1.214</h2.version>
+        <commons-dbutils.version>1.8.1</commons-dbutils.version>
+    </properties>
+</project>

persistence-modules/core-java-persistence-3/src/test/java/com/baeldung/resultsettomap/ResultSetToMapUnitTest.java

@@ -0,0 +1,107 @@
+package com.baeldung.resultsettomap;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.dbutils.QueryRunner;
+import org.apache.commons.dbutils.ResultSetHandler;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class ResultSetToMapUnitTest {
+    private static Connection connection = null;
+    private static final String JDBC_URL = "jdbc:h2:mem:testDatabase";
+    private static final String USERNAME = "dbUser";
+    private static final String PASSWORD = "dbPassword";
+
+    @Before
+    public void setup() throws Exception {
+        connection = DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
+        initialDataSetup();
+    }
+
+    private void initialDataSetup() throws SQLException {
+        Statement statement = connection.createStatement();
+        String ddlQuery = "CREATE TABLE employee (empId INTEGER not null, empName VARCHAR(50), empCity VARCHAR(50), PRIMARY KEY (empId))";
+        statement.execute(ddlQuery);
+        List<String> sqlQueryList = Arrays.asList("INSERT INTO employee VALUES (1, 'Steve','London')", "INSERT INTO employee VALUES (2, 'John','London')", "INSERT INTO employee VALUES (3, 'David', 'Sydney')",
+            "INSERT INTO employee VALUES (4, 'Kevin','London')", "INSERT INTO employee VALUES (5, 'Jade', 'Sydney')");
+
+        for (String query : sqlQueryList) {
+            statement.execute(query);
+        }
+    }
+
+    @Test
+    public void whenUsingContainsKey_thenConvertResultSetToMap() throws SQLException {
+        ResultSet resultSet = connection.prepareStatement("SELECT * FROM employee")
+            .executeQuery();
+        Map<String, List<String>> valueMap = new HashMap<>();
+
+        while (resultSet.next()) {
+            String empCity = resultSet.getString("empCity");
+            String empName = resultSet.getString("empName");
+            if (!valueMap.containsKey(empCity)) {
+                valueMap.put(empCity, new ArrayList<>());
+            }
+            valueMap.get(empCity)
+                .add(empName);
+        }
+        assertEquals(3, valueMap.get("London")
+            .size());
+    }
+
+    @Test
+    public void whenUsingComputeIfAbsent_thenConvertResultSetToMap() throws SQLException {
+        ResultSet resultSet = connection.prepareStatement("SELECT * FROM employee")
+            .executeQuery();
+        Map<String, List<String>> valueMap = new HashMap<>();
+
+        while (resultSet.next()) {
+            String empCity = resultSet.getString("empCity");
+            String empName = resultSet.getString("empName");
+            valueMap.computeIfAbsent(empCity, data -> new ArrayList<>())
+                .add(empName);
+        }
+        assertEquals(3, valueMap.get("London")
+            .size());
+    }
+
+    @Test
+    public void whenUsingDbUtils_thenConvertResultSetToMap() throws SQLException {
+
+        ResultSetHandler<Map<String, List<String>>> handler = new ResultSetHandler<Map<String, List<String>>>() {
+            public Map<String, List<String>> handle(ResultSet resultSet) throws SQLException {
+                Map<String, List<String>> result = new HashMap<>();
+                while (resultSet.next()) {
+                    String empCity = resultSet.getString("empCity");
+                    String empName = resultSet.getString("empName");
+                    result.computeIfAbsent(empCity, data -> new ArrayList<>())
+                        .add(empName);
+                }
+                return result;
+            }
+        };
+
+        QueryRunner run = new QueryRunner();
+        Map<String, List<String>> valueMap = run.query(connection, "SELECT * FROM employee", handler);
+        assertEquals(3, valueMap.get("London")
+            .size());
+    }
+
+    @After
+    public void preDestroy() throws Exception {
+        connection.close();
+    }
+}

persistence-modules/pom.xml

@@ -21,6 +21,7 @@
         <module>blaze-persistence</module>
         <module>core-java-persistence</module>
         <module>core-java-persistence-2</module>
+        <module>core-java-persistence-3</module>
         <module>couchbase</module>
         <module>elasticsearch</module>
         <module>flyway</module>