BAEL-6081: Add code examples from article (#13861)

* BAEL-6081: Add code examples from article

* BAEL-6081: Fix formatting

libraries-data-db/src/main/java/com/baeldung/libraries/h2/H2InitDemoApplication.java

@@ -0,0 +1,72 @@
+package com.baeldung.libraries.h2;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationContext;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.DriverManager;
+
+@SpringBootApplication
+public class H2InitDemoApplication {
+
+    public static void main(String[] args) {
+        ApplicationContext ctx = SpringApplication.run(H2InitDemoApplication.class, args);
+        initDatabaseUsingPlainJDBCWithURL();
+        initDatabaseUsingPlainJDBCWithFile();
+        initDatabaseUsingSpring(ctx.getBean(DataSource.class));
+    }
+
+    /**
+     * Initialize in-memory database using plain JDBC and SQL
+     * statements in the URL.
+     */
+    private static void initDatabaseUsingPlainJDBCWithURL() {
+        try (Connection conn = DriverManager.
+            getConnection("jdbc:h2:mem:baeldung;INIT=CREATE SCHEMA IF NOT EXISTS baeldung\\;SET SCHEMA baeldung;",
+                "admin",
+                "password")) {
+            conn.createStatement().execute("create table users (name VARCHAR(100) NOT NULL, email VARCHAR(100) NOT NULL);");
+            System.out.println("Created table users");
+            conn.createStatement().execute("insert into users (name, email) values ('Mike', 'mike@baeldung.com')");
+            System.out.println("Added user mike");
+        }
+        catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    /**
+     * Initialize in-memory database using plain JDBC and SQL
+     * statements in a file.
+     */
+    private static void initDatabaseUsingPlainJDBCWithFile() {
+        try (Connection conn = DriverManager.
+            getConnection("jdbc:h2:mem:baeldung;INIT=RUNSCRIPT FROM 'src/main/resources/h2init.sql';",
+                "admin",
+                "password")) {
+            conn.createStatement().execute("insert into users (name, email) values ('Mike', 'mike@baeldung.com')");
+            System.out.println("Added user mike");
+        }
+        catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    /**
+     * Initialize in-memory database using Spring Boot
+     * properties. See article for full details of required
+     * properties for this method to work.
+     */
+    private static void initDatabaseUsingSpring(DataSource ds) {
+        try (Connection conn = ds.getConnection()) {
+            conn.createStatement().execute("insert into users (name, email) values ('Mike', 'mike@baeldung.com')");
+            System.out.println("Added user mike");
+        }
+        catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}
+

libraries-data-db/src/main/resources/h2init.sql

@@ -0,0 +1,3 @@
+CREATE SCHEMA IF NOT EXISTS baeldung;
+SET SCHEMA baeldung;
+CREATE TABLE users (name VARCHAR(100) NOT NULL, email VARCHAR(100) NOT NULL);