refactor: RequestLine의 httpMethod enum으로 변경 및 커스텀 예외 추가

tomcat/src/main/java/org/apache/coyote/http11/exception/InvalidRequestException.java

@@ -0,0 +1,8 @@
+package org.apache.coyote.http11.exception;
+
+public class InvalidRequestException extends RuntimeException {
+
+    public InvalidRequestException() {
+        super("유효하지 않은 요청입니다.");
+    }
+}

tomcat/src/main/java/org/apache/coyote/http11/request/RequestLine.java

@@ -1,26 +1,29 @@
 package org.apache.coyote.http11.request;
 
+import org.apache.coyote.http11.exception.InvalidRequestException;
+
 public class RequestLine {
 
-    private final String requestMethod;
+    private final RequestMethod requestMethod;
     private final String requestUrl;
     private final String requestProtocol;
 
-    public RequestLine(final String requestMethod, final String requestUrl, final String requestProtocol) {
+    public RequestLine(final RequestMethod requestMethod, final String requestUrl, final String requestProtocol) {
         this.requestMethod = requestMethod;
         this.requestUrl = requestUrl;
         this.requestProtocol = requestProtocol;
     }
 
     public static RequestLine from(final String line) {
         String[] requestParts = line.split(" ");
-        if(requestParts.length != 3) {
-            throw new IllegalArgumentException(); //todo : 유효하지 않은 헤더 예외처리
+        if (requestParts.length != 3) {
+            throw new InvalidRequestException();
         }
-        return new RequestLine(requestParts[0], requestParts[1], requestParts[2]);
+        RequestMethod requestMethod = RequestMethod.getRequestMethod(requestParts[0]);
+        return new RequestLine(requestMethod, requestParts[1], requestParts[2]);
     }
 
-    public String getRequestMethod() {
+    public RequestMethod getRequestMethod() {
         return requestMethod;
     }
 

tomcat/src/main/java/org/apache/coyote/http11/request/RequestMethod.java

@@ -0,0 +1,24 @@
+package org.apache.coyote.http11.request;
+
+import org.apache.coyote.http11.exception.InvalidRequestException;
+
+import java.util.Arrays;
+
+public enum RequestMethod {
+    GET,
+    POST,
+    PATCH,
+    UPDATE,
+    DELETE,
+    ;
+
+    RequestMethod() {
+    }
+
+    public static RequestMethod getRequestMethod(String value) {
+        return Arrays.stream(RequestMethod.values())
+                .filter(requestMethod -> requestMethod.name().equals(value))
+                .findFirst()
+                .orElseThrow(InvalidRequestException::new);
+    }
+}