BAEL-2988 Using Enums as Request Parameters in Spring (#7815)

* BAEL-2988 Using Enums as Request Parameters in Spring

* Remove the unused annotation based on PR feedback

* Simplify code based on the PR feedback

* Make the methods consistent with the article.

spring-rest-simple/src/main/java/com/baeldung/Application.java

@@ -4,11 +4,9 @@ import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
-import org.springframework.context.annotation.ComponentScan;
 
 @EnableAutoConfiguration
 @SpringBootApplication
-@ComponentScan("com.baeldung.cors")
 public class Application extends SpringBootServletInitializer {
 
     public static void main(final String[] args) {

spring-rest-simple/src/main/java/com/baeldung/config/MvcConfig.java

@@ -2,6 +2,7 @@ package com.baeldung.config;
 
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.format.FormatterRegistry;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.StringHttpMessageConverter;
@@ -17,6 +18,7 @@ import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 import com.baeldung.config.converter.KryoHttpMessageConverter;
+import com.baeldung.config.converter.StringToEnumConverter;
 
 import java.text.SimpleDateFormat;
 import java.util.List;
@@ -71,4 +73,9 @@ public class MvcConfig implements WebMvcConfigurer {
     public void addCorsMappings(CorsRegistry registry) {
         registry.addMapping("/**");
     }
+
+    @Override
+    public void addFormatters(FormatterRegistry registry) {
+       registry.addConverter(new StringToEnumConverter());
+    }
 }

spring-rest-simple/src/main/java/com/baeldung/config/converter/StringToEnumConverter.java

@@ -0,0 +1,20 @@
+package com.baeldung.config.converter;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.stereotype.Component;
+
+import com.baeldung.model.Modes;
+
+@Component
+public class StringToEnumConverter implements Converter<String, Modes> {
+    @Override
+    public Modes convert(String source) {
+        // Remove the try-catch block if we want to handle the exception globally in GlobalControllerExceptionHandler
+        try {
+            return Modes.valueOf(source.toUpperCase());
+        } catch (IllegalArgumentException e) {
+            return null;
+        }
+
+    }
+}

spring-rest-simple/src/main/java/com/baeldung/cors/EnumController.java

@@ -0,0 +1,25 @@
+package com.baeldung.cors;
+
+import org.springframework.web.bind.annotation.CrossOrigin;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+import com.baeldung.model.Modes;
+
+@CrossOrigin(maxAge = 3600)
+@RestController
+@RequestMapping("/enums")
+public class EnumController {
+
+    @RequestMapping("/mode2str")
+    public String getStringToMode(@RequestParam("mode") Modes mode) {
+        return "good";
+    }
+
+    @RequestMapping("/findbymode/{mode}")
+    public String findByEnum(@PathVariable Modes mode) {
+        return "good";
+    }
+}

spring-rest-simple/src/main/java/com/baeldung/exceptions/GlobalControllerExceptionHandler.java

@@ -0,0 +1,16 @@
+package com.baeldung.exceptions;
+
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+
+@ControllerAdvice
+public class GlobalControllerExceptionHandler {
+    @ExceptionHandler(ConversionFailedException.class)
+    public ResponseEntity<String> handleConflict(RuntimeException ex) {
+        // Remove the try-catch block in the StringToEnumConverter if we want to handle the exception here
+        return new ResponseEntity<>(ex.getMessage(), HttpStatus.BAD_REQUEST);
+    }
+}

spring-rest-simple/src/main/java/com/baeldung/model/Modes.java

@@ -0,0 +1,5 @@
+package com.baeldung.model;
+
+public enum Modes {
+    ALPHA, DELTA
+}