Allow multiple readers/writers to be @ActuatorMetric*

In principle you might have multiple "system" repositories, all
of which you want to go to public metrics or not be metrics exporters.
This change adds a new annotation and renames the old one, so that
reades and writers can be distinguished, and also changes the
autowiring of them to accept multiple values.

Also adds automatic public metrics for Spring Integration.

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/integration/SpringIntegrationMetricReaderTests.java

@@ -0,0 +1,43 @@
+package org.springframework.boot.actuate.metrics.integration;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.actuate.metrics.integration.SpringIntegrationMetricReaderTests.TestConfiguration;
+import org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration;
+import org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration;
+import org.springframework.boot.test.IntegrationTest;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.integration.monitor.IntegrationMBeanExporter;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes=TestConfiguration.class)
+@IntegrationTest("spring.jmx.enabled=true")
+@DirtiesContext
+public class SpringIntegrationMetricReaderTests {
+	
+	@Autowired
+	private SpringIntegrationMetricReader reader;
+
+	@Test
+	public void test() {
+		assertTrue(reader.count()>0);
+	}
+	
+	@Configuration
+	@Import({JmxAutoConfiguration.class, IntegrationAutoConfiguration.class})
+	protected static class TestConfiguration {
+		@Bean
+		public SpringIntegrationMetricReader reader(IntegrationMBeanExporter exporter) {
+			return new SpringIntegrationMetricReader(exporter);
+		}
+	}
+
+}