Add generic error handling to BasicErrorController

Since Spring supports gobal error handling through
@ControllerAdvice, it is quite easy to set up more meta-data
about an exception for the BasicErrorController. You need
to be careful not to swallow Security exceptions, and probably
others (optionally) so this feature needs a bit more work.

See gh-538

spring-boot-samples/spring-boot-sample-actuator/src/main/java/sample/actuator/SampleController.java

@@ -17,12 +17,17 @@
 package sample.actuator;
 
 import java.util.Collections;
+import java.util.Date;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
+import org.hibernate.validator.constraints.NotBlank;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Description;
 import org.springframework.stereotype.Controller;
+import org.springframework.validation.annotation.Validated;
 import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.ResponseBody;
 
 @Controller
@@ -32,16 +37,42 @@ public class SampleController {
 	@Autowired
 	private HelloWorldService helloWorldService;
 
-	@RequestMapping("/")
+	@RequestMapping(value="/",  method=RequestMethod.GET)
 	@ResponseBody
-	public Map<String, String> helloWorld() {
+	public Map<String, String> hello() {
 		return Collections.singletonMap("message",
 				this.helloWorldService.getHelloMessage());
 	}
 
+	@RequestMapping(value="/", method=RequestMethod.POST)
+	@ResponseBody
+	public Map<String, Object> olleh(@Validated Message message) {
+		Map<String, Object> model = new LinkedHashMap<String, Object>();
+		model .put("message", message.getValue());
+		model.put("title", "Hello Home");
+		model.put("date", new Date());
+		return model;
+	}
+
 	@RequestMapping("/foo")
 	@ResponseBody
 	public String foo() {
 		throw new IllegalArgumentException("Server error");
 	}
+	
+	protected static class Message {
+		
+		@NotBlank(message="Message value cannot be empty")
+		private String value;
+
+		public String getValue() {
+			return value;
+		}
+
+		public void setValue(String value) {
+			this.value = value;
+		}
+	}
+
+
 }