Extract metric export into a separate autoconfig class

This avoids a potential problems with ordering between Dropwizard and
normal repository configuration. A Dropwizard sample has been added to
verify the behaviour.

spring-boot-samples/spring-boot-sample-metrics-dropwizard/src/test/java/sample/metrics/dropwizard/SampleDropwizardMetricsApplicationTests.java

@@ -0,0 +1,57 @@
+/*
+ * 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 sample.metrics.dropwizard;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.actuate.metrics.GaugeService;
+import org.springframework.boot.test.IntegrationTest;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+
+import com.codahale.metrics.MetricRegistry;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Basic integration tests for {@link SampleDropwizardMetricsApplication}.
+ *
+ * @author Dave Syer
+ */
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = SampleDropwizardMetricsApplication.class)
+@WebAppConfiguration
+@IntegrationTest("server.port=0")
+@DirtiesContext
+public class SampleDropwizardMetricsApplicationTests {
+
+	@Autowired
+	private MetricRegistry registry;
+
+	@Autowired
+	private GaugeService gauges;
+
+	@Test
+	public void timerCreated() {
+		this.gauges.submit("timer.test", 1234);
+		assertEquals(1, this.registry.getTimers().get("timer.test").getCount());
+	}
+
+}