Add FlywayMigrationStrategy support

Update FlywayAutoConfiguration to support pluggable migration
strategies. Rather than always calling flyway.migrate(), users can now
provide a FlywayMigrationStrategy @Bean to call whatever methods they
wish.

Fixes gh-1814

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/jpa/EntityManagerFactoryDependsOnPostProcessor.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,9 +45,9 @@ import org.springframework.util.StringUtils;
 public class EntityManagerFactoryDependsOnPostProcessor implements
 		BeanFactoryPostProcessor {
 
-	private final String dependsOn;
+	private final String[] dependsOn;
 
-	public EntityManagerFactoryDependsOnPostProcessor(String dependsOn) {
+	public EntityManagerFactoryDependsOnPostProcessor(String... dependsOn) {
 		this.dependsOn = dependsOn;
 	}
 
@@ -55,8 +55,11 @@ public class EntityManagerFactoryDependsOnPostProcessor implements
 	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
 		for (String beanName : getEntityManagerFactoryBeanNames(beanFactory)) {
 			BeanDefinition definition = getBeanDefinition(beanName, beanFactory);
-			definition.setDependsOn(StringUtils.addStringToArray(
-					definition.getDependsOn(), this.dependsOn));
+			String[] dependencies = definition.getDependsOn();
+			for (String bean : this.dependsOn) {
+				dependencies = StringUtils.addStringToArray(dependencies, bean);
+			}
+			definition.setDependsOn(dependencies);
 		}
 	}
 

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,7 @@ import javax.persistence.EntityManagerFactory;
 import javax.sql.DataSource;
 
 import org.flywaydb.core.Flyway;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -95,7 +96,13 @@ public class FlywayAutoConfiguration {
 			return false;
 		}
 
-		@Bean(initMethod = "migrate")
+		@Bean
+		@ConditionalOnMissingBean
+		public FlywayMigrationStrategy flywayMigrationStrategy() {
+			return new FlywayMigrationStrategy();
+		}
+
+		@Bean
 		@ConfigurationProperties(prefix = "flyway")
 		public Flyway flyway() {
 			Flyway flyway = new Flyway();
@@ -113,6 +120,13 @@ public class FlywayAutoConfiguration {
 			return flyway;
 		}
 
+		@Bean
+		public FlywayMigrationInitializer flywayInitializer(Flyway flyway,
+				FlywayMigrationStrategy migrationStrategy) {
+			return new FlywayMigrationInitializer(flyway, migrationStrategy);
+
+		}
+
 	}
 
 	/**
@@ -126,7 +140,30 @@ public class FlywayAutoConfiguration {
 			EntityManagerFactoryDependsOnPostProcessor {
 
 		public FlywayJpaDependencyConfiguration() {
-			super("flyway");
+			super("flywayInitializer", "flyway");
+		}
+
+	}
+
+	/**
+	 * {@link InitializingBean} used to trigger {@link Flyway} migration via the
+	 * {@link FlywayMigrationStrategy}.
+	 */
+	private static class FlywayMigrationInitializer implements InitializingBean {
+
+		private final Flyway flyway;
+
+		private final FlywayMigrationStrategy migrationStrategy;
+
+		public FlywayMigrationInitializer(Flyway flyway,
+				FlywayMigrationStrategy migrationStrategy) {
+			this.flyway = flyway;
+			this.migrationStrategy = migrationStrategy;
+		}
+
+		@Override
+		public void afterPropertiesSet() throws Exception {
+			this.migrationStrategy.migrate(this.flyway);
 		}
 
 	}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayMigrationStrategy.java

+/*
+ * Copyright 2012-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.flyway;
+
+import org.flywaydb.core.Flyway;
+
+/**
+ * Strategy used to initialize {@link Flyway} migration. Custom implementations may be
+ * registered as a {@code @Bean} to override the default migration behavior.
+ *
+ * @author Andreas Ahlenstorf
+ * @author Phillip Webb
+ */
+public class FlywayMigrationStrategy {
+
+	public void migrate(Flyway flyway) {
+		flyway.migrate();
+	}
+
+}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/flyway/FlywayAutoConfigurationTests.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,9 +34,12 @@ import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.stereotype.Component;
 
+import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
 
 /**
  * Tests for {@link FlywayAutoConfiguration}.
@@ -148,6 +151,16 @@ public class FlywayAutoConfigurationTests {
 				FlywayAutoConfiguration.class, PropertyPlaceholderAutoConfiguration.class);
 	}
 
+	@Test
+	public void customFlywayMigrationStrategy() throws Exception {
+		registerAndRefresh(EmbeddedDataSourceConfiguration.class,
+				FlywayAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class,
+				MockFlywayMigrationStrategy.class);
+		assertNotNull(this.context.getBean(Flyway.class));
+		this.context.getBean(MockFlywayMigrationStrategy.class).assertCalled();
+	}
+
 	private void registerAndRefresh(Class<?>... annotatedClasses) {
 		this.context.register(annotatedClasses);
 		this.context.refresh();
@@ -165,4 +178,20 @@ public class FlywayAutoConfigurationTests {
 		}
 
 	}
+
+	@Component
+	protected static class MockFlywayMigrationStrategy extends FlywayMigrationStrategy {
+
+		private boolean called = false;
+
+		@Override
+		public void migrate(Flyway flyway) {
+			this.called = true;
+		}
+
+		public void assertCalled() {
+			assertThat(this.called, equalTo(true));
+		}
+	}
+
 }