Polish "Use custom DataSource if Flyway or Liquibase has user or url"

Closes gh-11751

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

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -22,6 +22,7 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.function.Supplier;
 
 import javax.persistence.EntityManagerFactory;
 import javax.sql.DataSource;
@@ -129,18 +130,12 @@ public class FlywayAutoConfiguration {
 		public Flyway flyway() {
 			Flyway flyway = new SpringBootFlyway();
 			if (this.properties.isCreateDataSource()) {
-				String url = this.properties.getUrl() == null
-						? this.dataSourceProperties.getUrl()
-						: this.properties.getUrl();
-
-				String user = this.properties.getUser() == null
-						? this.dataSourceProperties.getUsername()
-						: this.properties.getUser();
-
-				String password = this.properties.getPassword() == null
-						? this.dataSourceProperties.getPassword()
-						: this.properties.getPassword();
-
+				String url = getProperty(this.properties::getUrl,
+						this.dataSourceProperties::getUrl);
+				String user = getProperty(this.properties::getUser,
+						this.dataSourceProperties::getUsername);
+				String password = getProperty(this.properties::getPassword,
+						this.dataSourceProperties::getPassword);
 				flyway.setDataSource(url, user, password,
 						this.properties.getInitSqls().toArray(new String[0]));
 			}
@@ -159,13 +154,20 @@ public class FlywayAutoConfiguration {
 			return flyway;
 		}
 
+		private String getProperty(Supplier<String> property,
+				Supplier<String> defaultValue) {
+			String value = property.get();
+			return value == null ? defaultValue.get() : value;
+		}
+
 		private void checkLocationExists(String... locations) {
 			if (this.properties.isCheckLocation()) {
 				Assert.state(locations.length != 0,
 						"Migration script locations not configured");
 				boolean exists = hasAtLeastOneLocation(locations);
-				Assert.state(exists, () -> "Cannot find migrations location in: "
-						+ Arrays.asList(locations)
+				Assert.state(exists,
+						() -> "Cannot find migrations location in: " + Arrays.asList(
+								locations)
 						+ " (please add migrations or check your Flyway configuration)");
 			}
 		}

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

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/liquibase/LiquibaseAutoConfiguration.java

@@ -19,6 +19,7 @@ package org.springframework.boot.autoconfigure.liquibase;
 import java.lang.reflect.Method;
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Supplier;
 
 import javax.annotation.PostConstruct;
 import javax.persistence.EntityManagerFactory;
@@ -153,22 +154,22 @@ public class LiquibaseAutoConfiguration {
 		}
 
 		private DataSource createNewDataSource() {
-			String url = this.properties.getUrl() == null
-					? this.dataSourceProperties.getUrl()
-					: this.properties.getUrl();
-
-			String user = this.properties.getUser() == null
-					? this.dataSourceProperties.getUsername()
-					: this.properties.getUser();
-
-			String password = this.properties.getPassword() == null
-					? this.dataSourceProperties.getPassword()
-					: this.properties.getPassword();
-
+			String url = getProperty(this.properties::getUrl,
+					this.dataSourceProperties::getUrl);
+			String user = getProperty(this.properties::getUser,
+					this.dataSourceProperties::getUsername);
+			String password = getProperty(this.properties::getPassword,
+					this.dataSourceProperties::getPassword);
 			return DataSourceBuilder.create().url(url).username(user).password(password)
 					.build();
 		}
 
+		private String getProperty(Supplier<String> property,
+				Supplier<String> defaultValue) {
+			String value = property.get();
+			return value == null ? defaultValue.get() : value;
+		}
+
 	}
 
 	/**

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

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.

spring-boot-project/spring-boot-docs/src/main/asciidoc/howto.adoc

@@ -2139,7 +2139,10 @@ uses that for migrations. If you like to use a different `DataSource`, you can c
 one and mark its `@Bean` as `@FlywayDataSource`. If you do so and want two data sources,
 remember to create another one and mark it as `@Primary`. Alternatively, you can use
 Flyway's native `DataSource` by setting `spring.flyway.[url,user,password]`
-in external properties.
+in external properties. Setting either `spring.flyway.url` or `spring.flyway.user`
+is sufficent to cause Flyway to use its own `DataSource`. If any of the three
+properties has not be set, the value of its equivalent `spring.datasource` property will
+be used.
 
 There is a {github-code}/spring-boot-samples/spring-boot-sample-flyway[Flyway sample] so
 that you can see how to set things up.
@@ -2175,7 +2178,10 @@ that for migrations. If you need to use a different `DataSource`, you can create
 mark its `@Bean` as `@LiquibaseDataSource`. If you do so and you want two data sources,
 remember to create another one and mark it as `@Primary`. Alternatively, you can use
 Liquibase's native `DataSource` by setting `spring.liquibase.[url,user,password]` in
-external properties.
+external properties. Setting either `spring.liquibase.url` or `spring.liquibase.user`
+is sufficent to cause Liquibase to use its own `DataSource`. If any of the three
+properties has not be set, the value of its equivalent `spring.datasource` property will
+be used.
 
 See
 {sc-spring-boot-autoconfigure}/liquibase/LiquibaseProperties.{sc-ext}[`LiquibaseProperties`]