Polish

spring-test/src/main/java/org/springframework/test/web/reactive/server/AbstractMockServerSpec.java

@@ -20,7 +20,8 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import org.springframework.util.Assert;
+import org.springframework.lang.Nullable;
+import org.springframework.util.CollectionUtils;
 import org.springframework.web.server.WebFilter;
 import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
 import org.springframework.web.server.session.DefaultWebSessionManager;
@@ -36,22 +37,33 @@ import org.springframework.web.server.session.WebSessionManager;
 abstract class AbstractMockServerSpec<B extends WebTestClient.MockServerSpec<B>>
 		implements WebTestClient.MockServerSpec<B> {
 
-	private final List<WebFilter> filters = new ArrayList<>(4);
+	@Nullable
+	private List<WebFilter> filters;
 
-	private WebSessionManager sessionManager = new DefaultWebSessionManager();
+	@Nullable
+	private WebSessionManager sessionManager;
 
-	private final List<MockServerConfigurer> configurers = new ArrayList<>(4);
+	@Nullable
+	private List<MockServerConfigurer> configurers;
+
+
+	AbstractMockServerSpec() {
+		// Default instance to be re-used across requests, unless one is configured explicitly
+		this.sessionManager = new DefaultWebSessionManager();
+	}
 
 
 	@Override
-	public <T extends B> T webFilter(WebFilter... filter) {
-		this.filters.addAll(Arrays.asList(filter));
+	public <T extends B> T webFilter(WebFilter... filters) {
+		if (filters.length > 0) {
+			this.filters = (this.filters != null ? this.filters : new ArrayList<>(4));
+			this.filters.addAll(Arrays.asList(filters));
+		}
 		return self();
 	}
 
 	@Override
 	public <T extends B> T webSessionManager(WebSessionManager sessionManager) {
-		Assert.notNull(sessionManager, "WebSessionManager must not be null.");
 		this.sessionManager = sessionManager;
 		return self();
 	}
@@ -59,6 +71,7 @@ abstract class AbstractMockServerSpec<B extends WebTestClient.MockServerSpec<B>>
 	@Override
 	public <T extends B> T apply(MockServerConfigurer configurer) {
 		configurer.afterConfigureAdded(this);
+		this.configurers = (this.configurers != null ? this.configurers : new ArrayList<>(4));
 		this.configurers.add(configurer);
 		return self();
 	}
@@ -71,9 +84,15 @@ abstract class AbstractMockServerSpec<B extends WebTestClient.MockServerSpec<B>>
 	@Override
 	public WebTestClient.Builder configureClient() {
 		WebHttpHandlerBuilder builder = initHttpHandlerBuilder();
-		builder.filters(theFilters -> theFilters.addAll(0, this.filters));
-		builder.sessionManager(this.sessionManager);
-		this.configurers.forEach(configurer -> configurer.beforeServerCreated(builder));
+		if (!CollectionUtils.isEmpty(this.filters)) {
+			builder.filters(theFilters -> theFilters.addAll(0, this.filters));
+		}
+		if (this.sessionManager != null) {
+			builder.sessionManager(this.sessionManager);
+		}
+		if (!CollectionUtils.isEmpty(this.configurers)) {
+			this.configurers.forEach(configurer -> configurer.beforeServerCreated(builder));
+		}
 		return new DefaultWebTestClientBuilder(builder);
 	}