Add a property to configure the connection pool

A new `spring.datasource.type` property can now be used to configure the
connection pool implementation to use (rather than only relying on Boot's
preferences).

Closes gh-3705

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceAutoConfiguration.java

@@ -120,6 +120,9 @@ public class DataSourceAutoConfiguration {
 					.url(this.properties.getUrl())
 					.username(this.properties.getUsername())
 					.password(this.properties.getPassword());
+			if (this.properties.getType() != null) {
+				factory.type(this.properties.getType());
+			}
 			return factory.build();
 		}
 

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceProperties.java

@@ -19,6 +19,7 @@ package org.springframework.boot.autoconfigure.jdbc;
 import java.nio.charset.Charset;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import javax.sql.DataSource;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.BeanCreationException;
@@ -33,6 +34,7 @@ import org.springframework.util.StringUtils;
  *
  * @author Dave Syer
  * @author Maciej Walkowiak
+ * @author Stephane Nicoll
  * @since 1.1.0
  */
 @ConfigurationProperties(prefix = DataSourceProperties.PREFIX)
@@ -40,6 +42,12 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 
 	public static final String PREFIX = "spring.datasource";
 
+	/**
+	 * Fully qualified name of the connection pool implementation to use. By default,
+	 * it is auto-detected from the classpath.
+	 */
+	private Class<? extends DataSource> type;
+
 	/**
 	 * Fully qualified name of the JDBC driver. Auto-detected based on the URL by default.
 	 */
@@ -118,6 +126,14 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 				.get(this.classLoader);
 	}
 
+	public Class<? extends DataSource> getType() {
+		return type;
+	}
+
+	public void setType(Class<? extends DataSource> type) {
+		this.type = type;
+	}
+
 	public String getDriverClassName() {
 		if (StringUtils.hasText(this.driverClassName)) {
 			Assert.state(ClassUtils.isPresent(this.driverClassName, null),
@@ -144,6 +160,10 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 		return driverClassName;
 	}
 
+	public void setDriverClassName(String driverClassName) {
+		this.driverClassName = driverClassName;
+	}
+
 	public String getUrl() {
 		if (StringUtils.hasText(this.url)) {
 			return this.url;
@@ -159,6 +179,10 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 		return url;
 	}
 
+	public void setUrl(String url) {
+		this.url = url;
+	}
+
 	public String getUsername() {
 		if (StringUtils.hasText(this.username)) {
 			return this.username;
@@ -169,6 +193,10 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 		return null;
 	}
 
+	public void setUsername(String username) {
+		this.username = username;
+	}
+
 	public String getPassword() {
 		if (StringUtils.hasText(this.password)) {
 			return this.password;
@@ -179,18 +207,6 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 		return null;
 	}
 
-	public void setDriverClassName(String driverClassName) {
-		this.driverClassName = driverClassName;
-	}
-
-	public void setUrl(String url) {
-		this.url = url;
-	}
-
-	public void setUsername(String username) {
-		this.username = username;
-	}
-
 	public void setPassword(String password) {
 		this.password = password;
 	}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jdbc/DataSourceAutoConfigurationTests.java

@@ -26,13 +26,14 @@ import java.sql.SQLFeatureNotSupportedException;
 import java.util.Properties;
 import java.util.Random;
 import java.util.logging.Logger;
-
 import javax.sql.DataSource;
 
+import com.zaxxer.hikari.HikariDataSource;
 import org.apache.commons.dbcp.BasicDataSource;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
+
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration;
 import org.springframework.boot.test.EnvironmentTestUtils;
@@ -42,8 +43,6 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
 
-import com.zaxxer.hikari.HikariDataSource;
-
 import static org.hamcrest.Matchers.instanceOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -56,6 +55,7 @@ import static org.mockito.Mockito.mock;
  * Tests for {@link DataSourceAutoConfiguration}.
  *
  * @author Dave Syer
+ * @author Stephane Nicoll
  */
 public class DataSourceAutoConfigurationTests {
 
@@ -72,9 +72,7 @@ public class DataSourceAutoConfigurationTests {
 	@After
 	public void restore() {
 		EmbeddedDatabaseConnection.override = null;
-		if (this.context != null) {
-			this.context.close();
-		}
+		this.context.close();
 	}
 
 	@Test
@@ -156,6 +154,20 @@ public class DataSourceAutoConfigurationTests {
 		assertEquals("sa", pool.getUsername());
 	}
 
+	@Test
+	public void explicitType() {
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.datasource.driverClassName:org.hsqldb.jdbcDriver",
+				"spring.datasource.url:jdbc:hsqldb:mem:testdb",
+				"spring.datasource.type:" + HikariDataSource.class.getName());
+		this.context.register(DataSourceAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class);
+		this.context.refresh();
+		DataSource bean = this.context.getBean(DataSource.class);
+		assertNotNull(bean);
+		assertEquals(HikariDataSource.class, bean.getClass());
+	}
+
 	@Test
 	public void testExplicitDriverClassClearsUserName() throws Exception {
 		EnvironmentTestUtils
@@ -259,6 +271,7 @@ public class DataSourceAutoConfigurationTests {
 
 	}
 
+	@SuppressWarnings("unused") // see testExplicitDriverClassClearsUserName
 	public static class DatabaseDriver implements Driver {
 
 		@Override

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -318,6 +318,7 @@ content into your application; rather pick only the properties that you need.
 	spring.datasource.platform= # the platform to use in the schema resource (schema-${platform}.sql)
 	spring.datasource.continue-on-error=false # continue even if can't be initialized
 	spring.datasource.separator=; # statement separator in SQL initialization scripts
+	spring.datasource.type= # fully qualified name of the connection pool implementation to use
 	spring.datasource.driver-class-name= # JDBC Settings...
 	spring.datasource.url=
 	spring.datasource.username=

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2047,8 +2047,10 @@ Here's the algorithm for choosing a specific implementation:
 If you use the `spring-boot-starter-jdbc` or `spring-boot-starter-data-jpa`
 '`starter POMs`' you will automatically get a dependency to `tomcat-jdbc`.
 
-NOTE: Additional connection pools can always be configured manually. If you define your
-own `DataSource` bean, auto-configuration will not occur.
+NOTE: You can bypass that algorithm completely and specify the connection pool to use via
+the `spring.datasource.type` property. Also, additional connection pools can always be
+configured manually. If you define your own `DataSource` bean, auto-configuration will
+not occur.
 
 DataSource configuration is controlled by external configuration properties in
 `+spring.datasource.*+`. For example, you might declare the following section in