Fix for NPE when no cookies set on request

http-server-jetty/src/test/groovy/io/micronaut/servlet/jetty/JettyCookieSpec.groovy

@@ -0,0 +1,68 @@
+package io.micronaut.servlet.jetty
+
+import io.micronaut.http.HttpRequest
+import io.micronaut.http.HttpResponse
+import io.micronaut.http.HttpStatus
+import io.micronaut.http.MutableHttpResponse
+import io.micronaut.http.annotation.Controller
+import io.micronaut.http.annotation.Filter
+import io.micronaut.http.annotation.Get
+import io.micronaut.http.client.RxHttpClient
+import io.micronaut.http.client.annotation.Client
+import io.micronaut.http.cookie.Cookies
+import io.micronaut.http.filter.HttpServerFilter
+import io.micronaut.http.filter.ServerFilterChain
+import io.micronaut.test.annotation.MockBean
+import io.micronaut.test.extensions.spock.annotation.MicronautTest
+import org.reactivestreams.Publisher
+import spock.lang.Issue
+import spock.lang.Specification
+
+import javax.inject.Inject
+
+@MicronautTest
+class JettyCookieSpec extends Specification {
+
+    @Inject
+    @Client("/")
+    RxHttpClient client
+
+    @Issue('https://github.com/micronaut-projects/micronaut-servlet/issues/52')
+    void 'test cookies are not null when no cookie is set on request'() {
+        given:
+        HttpRequest request = HttpRequest.GET('/cookie')
+
+        when:
+        HttpResponse response = client.exchange(request).blockingFirst()
+
+        then:
+        noExceptionThrown()
+        response.status == HttpStatus.ACCEPTED
+    }
+
+    @Controller('/cookie')
+    @MockBean
+    static class StatusController {
+        @Get
+        HttpStatus index() {
+            return HttpStatus.ACCEPTED
+        }
+    }
+
+    @Filter('/cookie/**')
+    @MockBean
+    static class MyFilter implements HttpServerFilter {
+
+        @Override
+        Publisher<MutableHttpResponse<?>> doFilter(HttpRequest<?> request, ServerFilterChain chain) {
+            Cookies cookies = request.cookies
+
+            if (cookies.isEmpty()) {
+                println 'Cookies are empty!'
+            }
+
+            return chain.proceed(request)
+        }
+    }
+
+}

servlet-engine/src/main/java/io/micronaut/servlet/engine/DefaultServletCookies.java

@@ -20,7 +20,11 @@
 import io.micronaut.http.cookie.Cookie;
 import io.micronaut.http.cookie.Cookies;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 /**
@@ -31,14 +35,20 @@
  */
 public class DefaultServletCookies implements Cookies {
 
+    private static final javax.servlet.http.Cookie[] EMPTY_COOKIES = new javax.servlet.http.Cookie[0];
+
     private final javax.servlet.http.Cookie[] cookies;
 
     /**
      * Default constructor.
      * @param cookies The cookies
      */
     public DefaultServletCookies(javax.servlet.http.Cookie[] cookies) {
-        this.cookies = cookies;
+        if (cookies == null) {
+            this.cookies = EMPTY_COOKIES;
+        } else {
+            this.cookies = cookies;
+        }
     }
 
     @Override