Add a configurable of beans to postprocess into refresh scope

Allows you to apply @RefreshScope to beans that you do not
control or define. The list is configurable as
spring.cloud.refresh.refreshable and by default has only
HikariDataSource.

Fixes gh-318

spring-cloud-context/src/test/java/org/springframework/cloud/autoconfigure/RefreshAutoConfigurationTests.java

@@ -5,14 +5,17 @@ import org.junit.Test;
 
 import org.springframework.boot.WebApplicationType;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
 import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.test.rule.OutputCapture;
+import org.springframework.cloud.context.refresh.ContextRefresher;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Configuration;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-
 /**
  * @author Dave Syer
  */
@@ -24,7 +27,7 @@ public class RefreshAutoConfigurationTests {
 	@Test
 	public void noWarnings() {
 		try (ConfigurableApplicationContext context = getApplicationContext(
-                WebApplicationType.NONE, Config.class)) {
+				WebApplicationType.NONE, Config.class)) {
 			assertThat(context.containsBean("refreshScope")).isTrue();
 			assertThat(output.toString()).doesNotContain("WARN");
 		}
@@ -33,19 +36,59 @@ public class RefreshAutoConfigurationTests {
 	@Test
 	public void disabled() {
 		try (ConfigurableApplicationContext context = getApplicationContext(
-                WebApplicationType.SERVLET, Config.class, "spring.cloud.refresh.enabled:false")) {
+				WebApplicationType.SERVLET, Config.class,
+				"spring.cloud.refresh.enabled:false")) {
 			assertThat(context.containsBean("refreshScope")).isFalse();
 		}
 	}
 
+	@Test
+	public void refreshables() {
+		try (ConfigurableApplicationContext context = getApplicationContext(
+				WebApplicationType.NONE, Config.class, "config.foo=bar",
+				"spring.cloud.refresh.refreshable:" + ConfigProps.class.getName())) {
+			context.getBean(ContextRefresher.class).refresh();
+		}
+	}
+
+	@Test
+	public void extraRefreshables() {
+		try (ConfigurableApplicationContext context = getApplicationContext(
+				WebApplicationType.NONE, Config.class, "config.foo=bar",
+				"spring.cloud.refresh.extra-refreshable:"
+						+ ConfigProps.class.getName())) {
+			context.getBean(ContextRefresher.class).refresh();
+		}
+	}
+
 	private static ConfigurableApplicationContext getApplicationContext(
-            WebApplicationType type, Class<?> configuration, String... properties) {
-		return new SpringApplicationBuilder(configuration).web(type).properties(properties).properties("server.port=0").run();
+			WebApplicationType type, Class<?> configuration, String... properties) {
+		return new SpringApplicationBuilder(configuration).web(type)
+				.properties(properties).properties("server.port=0").run();
 	}
 
 	@Configuration
-	@EnableAutoConfiguration
+	@EnableAutoConfiguration(exclude = DataSourceAutoConfiguration.class)
+	@EnableConfigurationProperties(ConfigProps.class)
 	static class Config {
 
 	}
+
+	@ConfigurationProperties("config")
+	static class ConfigProps {
+		private String foo;
+		private boolean sealed;
+
+		public String getFoo() {
+			return this.foo;
+		}
+
+		public void setFoo(String foo) {
+			if (this.sealed) {
+				throw new IllegalStateException("Cannot set sealed property");
+			}
+			this.foo = foo;
+			this.sealed = true;
+		}
+	}
 }