added code example using HikariCP in Boot 1.x and 2.x (#5007)

* added code example using HikariCP in Boot 1.x and 2.x

* code formatting

spring-4/pom.xml

@@ -19,6 +19,27 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-web</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.apache.tomcat</groupId>
+                    <artifactId>tomcat-jdbc</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>${h2database.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.zaxxer</groupId>
+            <artifactId>HikariCP</artifactId>
+            <version>${hikaricp.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>
@@ -58,6 +79,7 @@
         <flips-web.version>1.0.1</flips-web.version>
         <lombok.version>1.16.18</lombok.version>
         <java.version>1.8</java.version>
+        <h2database.version>1.4.197</h2database.version>
     </properties>
 
 </project>

spring-4/src/test/java/com/baeldung/connectionpool/ApplicationWithHikariConnectionPool.java

@@ -0,0 +1,12 @@
+package com.baeldung.connectionpool;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ApplicationWithHikariConnectionPool {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ApplicationWithHikariConnectionPool.class, args);
+    }
+}

spring-4/src/test/java/com/baeldung/connectionpool/HikariIntegrationTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.connectionpool;
+
+import static org.junit.Assert.*;
+
+import javax.sql.DataSource;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(
+    // instead of setting this property, we can exclude the dependency to org.apache.tomcat:tomcat-jdbc in pom.xml
+    properties = "spring.datasource.type=com.zaxxer.hikari.HikariDataSource")
+public class HikariIntegrationTest {
+
+    @Autowired
+    private DataSource dataSource;
+
+    @Test
+    public void hikariConnectionPoolIsConfigured() {
+        assertEquals("com.zaxxer.hikari.HikariDataSource", dataSource.getClass()
+            .getName());
+    }
+
+}

spring-5/src/test/java/com/baeldung/connectionpool/ApplicationWithHikariConnectionPool.java

@@ -0,0 +1,12 @@
+package com.baeldung.connectionpool;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ApplicationWithHikariConnectionPool {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ApplicationWithHikariConnectionPool.class, args);
+    }
+}

spring-5/src/test/java/com/baeldung/connectionpool/HikariIntegrationTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.connectionpool;
+
+import static org.junit.Assert.*;
+
+import javax.sql.DataSource;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class HikariIntegrationTest {
+
+    @Autowired
+    private DataSource dataSource;
+
+    @Test
+    public void hikariConnectionPoolIsConfigured() {
+        assertEquals("com.zaxxer.hikari.HikariDataSource", dataSource.getClass()
+            .getName());
+    }
+
+}