Ignore unresolvable nested placeholders

The NamePatternEnvironmentFilter used to throw an exception if
placeholders in property values could not be resolved.

Fixes gh-8510

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

@@ -22,8 +22,10 @@ import org.springframework.context.EnvironmentAware;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.EnumerablePropertySource;
 import org.springframework.core.env.Environment;
+import org.springframework.core.env.PropertyResolver;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.PropertySources;
+import org.springframework.core.env.PropertySourcesPropertyResolver;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.web.bind.annotation.GetMapping;
@@ -95,7 +97,14 @@ public class EnvironmentMvcEndpoint extends EndpointMvcAdapter
 
 		@Override
 		protected Object getOptionalValue(Environment source, String name) {
-			Object result = source.getProperty(name);
+			PropertyResolver resolver = source;
+			if (source instanceof ConfigurableEnvironment) {
+				resolver = new PropertySourcesPropertyResolver(
+						((ConfigurableEnvironment) source).getPropertySources());
+				((PropertySourcesPropertyResolver) resolver)
+						.setIgnoreUnresolvableNestedPlaceholders(true);
+			}
+			Object result = resolver.getProperty(name);
 			if (result != null) {
 				result = ((EnvironmentEndpoint) getDelegate()).sanitize(name, result);
 			}

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

@@ -102,6 +102,16 @@ public class EnvironmentMvcEndpointTests {
 				.andExpect(content().string(containsString("\"fool\":\"baz\"")));
 	}
 
+	@Test
+	public void nestedPathWhenPlaceholderCannotBeResolvedShouldReturnUnresolvedProperty() throws Exception {
+		Map<String, Object> map = new HashMap<String, Object>();
+		map.put("my.foo", "${my.bar}");
+		((ConfigurableEnvironment) this.context.getEnvironment()).getPropertySources()
+				.addFirst(new MapPropertySource("unresolved-placeholder", map));
+		this.mvc.perform(get("/env/my.*")).andExpect(status().isOk())
+				.andExpect(content().string(containsString("\"my.foo\":\"${my.bar}\"")));
+	}
+
 	@Configuration
 	@Import({ JacksonAutoConfiguration.class,
 			HttpMessageConvertersAutoConfiguration.class, WebMvcAutoConfiguration.class,