Improve EndpointHandlerMapping subclassing support

Update EndpointHandlerMapping so that it can be subclasses easily.
Subclasses can override the `path` that is used to map the endpoint,
allowing different mapping strategies to be used.

See gh-7108

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/mvc/EndpointHandlerMapping.java

@@ -27,6 +27,7 @@ import java.util.Set;
 import org.springframework.boot.actuate.endpoint.Endpoint;
 import org.springframework.context.ApplicationContext;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.servlet.HandlerMapping;
@@ -114,33 +115,44 @@ public class EndpointHandlerMapping extends RequestMappingHandlerMapping {
 			return;
 		}
 		String[] patterns = getPatterns(handler, mapping);
-		super.registerHandlerMethod(handler, method, withNewPatterns(mapping, patterns));
+		if (!ObjectUtils.isEmpty(patterns)) {
+			super.registerHandlerMethod(handler, method,
+					withNewPatterns(mapping, patterns));
+		}
 	}
 
 	private String[] getPatterns(Object handler, RequestMappingInfo mapping) {
-		String path = getPath(handler);
+		if (handler instanceof String) {
-		String prefix = StringUtils.hasText(this.prefix) ? this.prefix + path : path;
+			handler = getApplicationContext().getBean((String) handler);
+		}
+		Assert.state(handler instanceof MvcEndpoint, "Only MvcEndpoints are supported");
+		String path = getPath((MvcEndpoint) handler);
+		return (path == null ? null : getEndpointPatterns(path, mapping));
+	}
+
+	/**
+	 * Return the path that should be used to map the given {@link MvcEndpoint}.
+	 * @param endpoint the endpoint to map
+	 * @return the path to use for the endpoint or {@code null} if no mapping is required
+	 */
+	protected String getPath(MvcEndpoint endpoint) {
+		return endpoint.getPath();
+	}
+
+	private String[] getEndpointPatterns(String path, RequestMappingInfo mapping) {
+		String patternPrefix = StringUtils.hasText(this.prefix) ? this.prefix + path
+				: path;
 		Set<String> defaultPatterns = mapping.getPatternsCondition().getPatterns();
 		if (defaultPatterns.isEmpty()) {
-			return new String[] { prefix, prefix + ".json" };
+			return new String[] { patternPrefix, patternPrefix + ".json" };
 		}
 		List<String> patterns = new ArrayList<String>(defaultPatterns);
 		for (int i = 0; i < patterns.size(); i++) {
-			patterns.set(i, prefix + patterns.get(i));
+			patterns.set(i, patternPrefix + patterns.get(i));
 		}
 		return patterns.toArray(new String[patterns.size()]);
 	}
 
-	private String getPath(Object handler) {
-		if (handler instanceof String) {
-			handler = getApplicationContext().getBean((String) handler);
-		}
-		if (handler instanceof MvcEndpoint) {
-			return ((MvcEndpoint) handler).getPath();
-		}
-		return "";
-	}
-
 	private RequestMappingInfo withNewPatterns(RequestMappingInfo mapping,
 			String[] patternStrings) {
 		PatternsRequestCondition patterns = new PatternsRequestCondition(patternStrings,

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/mvc/EndpointHandlerMappingTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.actuate.endpoint.mvc;
 
 import java.lang.reflect.Method;
 import java.util.Arrays;
+import java.util.Collection;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -145,6 +146,19 @@ public class EndpointHandlerMappingTests {
 		assertThat(mapping.getEndpoints(TestMvcEndpoint.class)).containsExactly(endpoint);
 	}
 
+	@Test
+	public void pathNotMappedWhenGetPathReturnsNull() throws Exception {
+		TestMvcEndpoint endpoint = new TestMvcEndpoint(new TestEndpoint("a"));
+		TestActionEndpoint other = new TestActionEndpoint(new TestEndpoint("b"));
+		EndpointHandlerMapping mapping = new TestEndpointHandlerMapping(
+				Arrays.asList(endpoint, other));
+		mapping.setApplicationContext(this.context);
+		mapping.afterPropertiesSet();
+		assertThat(mapping.getHandlerMethods()).hasSize(1);
+		assertThat(mapping.getHandler(request("GET", "/a"))).isNull();
+		assertThat(mapping.getHandler(request("POST", "/b"))).isNotNull();
+	}
+
 	private MockHttpServletRequest request(String method, String requestURI) {
 		return new MockHttpServletRequest(method, requestURI);
 	}
@@ -184,4 +198,20 @@ public class EndpointHandlerMappingTests {
 
 	}
 
+	static class TestEndpointHandlerMapping extends EndpointHandlerMapping {
+
+		TestEndpointHandlerMapping(Collection<? extends MvcEndpoint> endpoints) {
+			super(endpoints);
+		}
+
+		@Override
+		protected String getPath(MvcEndpoint endpoint) {
+			if (endpoint instanceof TestActionEndpoint) {
+				return super.getPath(endpoint);
+			}
+			return null;
+		}
+
+	}
+
 }