Fix keycloak response parsing (#10)

* Fix keycloak response parsing

* Fix checkstyle

pom.xml

@@ -127,6 +127,12 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>
             <scope>test</scope>
+            <exclusions>
+                <exclusion>
+                    <groupId>com.vaadin.external.google</groupId>
+                    <artifactId>android-json</artifactId>
+                </exclusion>
+            </exclusions>
         </dependency>
         <dependency>
             <groupId>org.testcontainers</groupId>

src/main/java/dev/vality/beholder/exception/BadResponseException.java

@@ -0,0 +1,16 @@
+package dev.vality.beholder.exception;
+
+public class BadResponseException extends RuntimeException {
+
+    public BadResponseException(String message) {
+        super(message);
+    }
+
+    public BadResponseException(Throwable throwable) {
+        super(throwable);
+    }
+
+    public BadResponseException(String message, Throwable throwable) {
+        super(message, throwable);
+    }
+}

src/main/java/dev/vality/beholder/security/KeycloakService.java

@@ -1,7 +1,11 @@
 package dev.vality.beholder.security;
 
 import dev.vality.beholder.config.properties.KeycloakProperties;
+import dev.vality.beholder.exception.BadFormatException;
+import dev.vality.beholder.exception.BadResponseException;
 import lombok.RequiredArgsConstructor;
+import org.json.JSONException;
+import org.json.JSONObject;
 import org.keycloak.OAuth2Constants;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.ResponseEntity;
@@ -24,7 +28,22 @@ public class KeycloakService {
                         .build();
         ResponseEntity<String> response =
                 restTemplate.postForEntity(keycloakProperties.getUrl(), request, String.class);
-        return response.getBody();
+
+        if (!response.getStatusCode().is2xxSuccessful()) {
+            throw new BadResponseException(
+                    String.format("Keycloak response: code: %s, body: %s", response.getStatusCode(),
+                            response.getBody()));
+        }
+        return getAccessToken(response.getBody());
+    }
+
+    private String getAccessToken(String body) {
+        try {
+            JSONObject json = new JSONObject(body);
+            return json.getString("access_token");
+        } catch (JSONException e) {
+            throw new BadFormatException(e);
+        }
     }
 
 }