Fix http status code with unknown log level

This commit changes the http status code to 400 when an unknown log level
is specified.

Closes gh-8798
See gh-8813

Author: eddumelendez

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

@@ -22,7 +22,6 @@
 import org.springframework.boot.actuate.endpoint.LoggersEndpoint.LoggerLevels;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.logging.LogLevel;
-import org.springframework.http.HttpEntity;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -33,6 +32,7 @@
  *
  * @author Ben Hale
  * @author Kazuki Shimizu
+ * @author Eddú Meléndez
  * @since 1.5.0
  */
 @ConfigurationProperties(prefix = "endpoints.loggers")
@@ -69,9 +69,14 @@ public Object set(@PathVariable String name,
 			return getDisabledResponse();
 		}
 		String level = configuration.get("configuredLevel");
-		LogLevel logLevel = level == null ? null : LogLevel.valueOf(level.toUpperCase());
-		this.delegate.setLogLevel(name, logLevel);
-		return HttpEntity.EMPTY;
+		try {
+			LogLevel logLevel = level == null ? null : LogLevel.valueOf(level.toUpperCase());
+			this.delegate.setLogLevel(name, logLevel);
+			return ResponseEntity.ok().build();
+		}
+		catch (IllegalArgumentException ex) {
+			return ResponseEntity.badRequest().build();
+		}
 	}
 
 }

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

@@ -64,6 +64,7 @@
  *
  * @author Ben Hale
  * @author Phillip Webb
+ * @author Eddú Meléndez
  */
 @RunWith(SpringRunner.class)
 @SpringBootTest
@@ -169,6 +170,14 @@ public void setLoggerWhenDisabledShouldReturnNotFound() throws Exception {
 		verifyZeroInteractions(this.loggingSystem);
 	}
 
+	@Test
+	public void setLoggerWithWrongLogLevel() throws Exception {
+		this.mvc.perform(post("/loggers/ROOT").contentType(MediaType.APPLICATION_JSON)
+				.content("{\"configuredLevel\":\"other\"}"))
+				.andExpect(status().is4xxClientError());
+		verifyZeroInteractions(this.loggingSystem);
+	}
+
 	@Configuration
 	@Import({ JacksonAutoConfiguration.class,
 			HttpMessageConvertersAutoConfiguration.class,