Avoid ConstantConditions warnings suppression (plus related polishing)

Issue: SPR-15756

spring-test/src/main/java/org/springframework/mock/web/server/MockWebSession.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.mock.web.server;
 
 import java.time.Clock;
@@ -22,6 +23,8 @@ import java.util.Map;
 
 import reactor.core.publisher.Mono;
 
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.server.session.InMemoryWebSessionStore;
 
@@ -46,13 +49,14 @@ public class MockWebSession implements WebSession {
 		this(null);
 	}
 
-	@SuppressWarnings("ConstantConditions")
-	public MockWebSession(Clock clock) {
+	public MockWebSession(@Nullable Clock clock) {
 		InMemoryWebSessionStore sessionStore = new InMemoryWebSessionStore();
 		if (clock != null) {
 			sessionStore.setClock(clock);
 		}
-		this.delegate = sessionStore.createWebSession().block();
+		WebSession session = sessionStore.createWebSession().block();
+		Assert.state(session != null, "WebSession must not be null");
+		this.delegate = session;
 	}
 
 

spring-web/src/main/java/org/springframework/http/codec/support/ClientDefaultCodecsImpl.java

@@ -13,9 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.http.codec.support;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.function.Supplier;
 
@@ -79,7 +81,7 @@ class ClientDefaultCodecsImpl extends BaseDefaultCodecs implements ClientCodecCo
 
 	@Nullable
 	private Decoder<?> getSseDecoder() {
-		return this.sseDecoder != null ? this.sseDecoder : jackson2Present ? getJackson2JsonDecoder() : null;
+		return (this.sseDecoder != null ? this.sseDecoder : jackson2Present ? getJackson2JsonDecoder() : null);
 	}
 
 	@Override
@@ -87,10 +89,16 @@ class ClientDefaultCodecsImpl extends BaseDefaultCodecs implements ClientCodecCo
 		typedWriters.add(new MultipartHttpMessageWriter(getPartWriters(), new FormHttpMessageWriter()));
 	}
 
-	@SuppressWarnings("ConstantConditions")
 	private List<HttpMessageWriter<?>> getPartWriters() {
-		return this.multipartCodecs != null ?
-				this.multipartCodecs.getWriters() : this.partWritersSupplier.get();
+		if (this.multipartCodecs != null) {
+			return this.multipartCodecs.getWriters();
+		}
+		else if (this.partWritersSupplier != null) {
+			return this.partWritersSupplier.get();
+		}
+		else {
+			return Collections.emptyList();
+		}
 	}
 
 
@@ -101,7 +109,6 @@ class ClientDefaultCodecsImpl extends BaseDefaultCodecs implements ClientCodecCo
 
 		private final List<HttpMessageWriter<?>> writers = new ArrayList<>();
 
-
 		@Override
 		public ClientCodecConfigurer.MultipartCodecs encoder(Encoder<?> encoder) {
 			writer(new EncoderHttpMessageWriter<>(encoder));

spring-web/src/main/java/org/springframework/http/codec/support/DefaultClientCodecConfigurer.java

@@ -26,13 +26,11 @@ import org.springframework.http.codec.ClientCodecConfigurer;
  */
 public class DefaultClientCodecConfigurer extends BaseCodecConfigurer implements ClientCodecConfigurer {
 
-
 	public DefaultClientCodecConfigurer() {
 		super(new ClientDefaultCodecsImpl());
 		((ClientDefaultCodecsImpl) defaultCodecs()).setPartWritersSupplier(() -> getWritersInternal(true));
 	}
 
-
 	@Override
 	public ClientDefaultCodecs defaultCodecs() {
 		return (ClientDefaultCodecs) super.defaultCodecs();

spring-web/src/main/java/org/springframework/http/codec/support/DefaultServerCodecConfigurer.java

@@ -26,7 +26,6 @@ import org.springframework.http.codec.ServerCodecConfigurer;
  */
 public class DefaultServerCodecConfigurer extends BaseCodecConfigurer implements ServerCodecConfigurer {
 
-
 	public DefaultServerCodecConfigurer() {
 		super(new ServerDefaultCodecsImpl());
 	}

spring-web/src/test/java/org/springframework/mock/web/test/server/MockWebSession.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.mock.web.test.server;
 
 import java.time.Clock;
@@ -22,6 +23,8 @@ import java.util.Map;
 
 import reactor.core.publisher.Mono;
 
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.server.session.InMemoryWebSessionStore;
 
@@ -46,13 +49,14 @@ public class MockWebSession implements WebSession {
 		this(null);
 	}
 
-	@SuppressWarnings("ConstantConditions")
-	public MockWebSession(Clock clock) {
+	public MockWebSession(@Nullable Clock clock) {
 		InMemoryWebSessionStore sessionStore = new InMemoryWebSessionStore();
 		if (clock != null) {
 			sessionStore.setClock(clock);
 		}
-		this.delegate = sessionStore.createWebSession().block();
+		WebSession session = sessionStore.createWebSession().block();
+		Assert.state(session != null, "WebSession must not be null");
+		this.delegate = session;
 	}
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/resource/DefaultResourceResolverChain.java

@@ -44,7 +44,7 @@ class DefaultResourceResolverChain implements ResourceResolverChain {
 
 
 	public DefaultResourceResolverChain(@Nullable List<? extends ResourceResolver> resolvers) {
-		resolvers = resolvers != null ? resolvers : Collections.emptyList();
+		resolvers = (resolvers != null ? resolvers : Collections.emptyList());
 		DefaultResourceResolverChain chain = initChain(new ArrayList<>(resolvers));
 		this.resolver = chain.resolver;
 		this.nextChain = chain.nextChain;
@@ -52,40 +52,35 @@ class DefaultResourceResolverChain implements ResourceResolverChain {
 
 	private static DefaultResourceResolverChain initChain(ArrayList<? extends ResourceResolver> resolvers) {
 		DefaultResourceResolverChain chain = new DefaultResourceResolverChain(null, null);
-		ListIterator<? extends ResourceResolver> itr = resolvers.listIterator(resolvers.size());
-		while (itr.hasPrevious()) {
-			chain = new DefaultResourceResolverChain(itr.previous(), chain);
+		ListIterator<? extends ResourceResolver> it = resolvers.listIterator(resolvers.size());
+		while (it.hasPrevious()) {
+			chain = new DefaultResourceResolverChain(it.previous(), chain);
 		}
 		return chain;
 	}
 
-	private DefaultResourceResolverChain(@Nullable ResourceResolver resolver,
-			@Nullable ResourceResolverChain chain) {
-
+	private DefaultResourceResolverChain(@Nullable ResourceResolver resolver, @Nullable ResourceResolverChain chain) {
 		Assert.isTrue((resolver == null && chain == null) || (resolver != null && chain != null),
 				"Both resolver and resolver chain must be null, or neither is");
-
 		this.resolver = resolver;
 		this.nextChain = chain;
 	}
 
 
 	@Override
-	@SuppressWarnings("ConstantConditions")
 	public Mono<Resource> resolveResource(@Nullable ServerWebExchange exchange, String requestPath,
 			List<? extends Resource> locations) {
 
-		return this.resolver != null ?
+		return (this.resolver != null && this.nextChain != null ?
 				this.resolver.resolveResource(exchange, requestPath, locations, this.nextChain) :
-				Mono.empty();
+				Mono.empty());
 	}
 
 	@Override
-	@SuppressWarnings("ConstantConditions")
 	public Mono<String> resolveUrlPath(String resourcePath, List<? extends Resource> locations) {
-		return this.resolver != null ?
+		return (this.resolver != null && this.nextChain != null ?
 				this.resolver.resolveUrlPath(resourcePath, locations, this.nextChain) :
-				Mono.empty();
+				Mono.empty());
 	}
 
 }

spring-webflux/src/main/java/org/springframework/web/reactive/resource/DefaultResourceTransformerChain.java

@@ -45,13 +45,12 @@ class DefaultResourceTransformerChain implements ResourceTransformerChain {
 	private final ResourceTransformerChain nextChain;
 
 
-	public DefaultResourceTransformerChain(ResourceResolverChain resolverChain,
-			@Nullable List<ResourceTransformer> transformers) {
+	public DefaultResourceTransformerChain(
+			ResourceResolverChain resolverChain, @Nullable List<ResourceTransformer> transformers) {
 
 		Assert.notNull(resolverChain, "ResourceResolverChain is required");
 		this.resolverChain = resolverChain;
-
-		transformers = transformers != null ? transformers : Collections.emptyList();
+		transformers = (transformers != null ? transformers : Collections.emptyList());
 		DefaultResourceTransformerChain chain = initTransformerChain(resolverChain, new ArrayList<>(transformers));
 		this.transformer = chain.transformer;
 		this.nextChain = chain.nextChain;
@@ -61,9 +60,9 @@ class DefaultResourceTransformerChain implements ResourceTransformerChain {
 			ArrayList<ResourceTransformer> transformers) {
 
 		DefaultResourceTransformerChain chain = new DefaultResourceTransformerChain(resolverChain, null, null);
-		ListIterator<? extends ResourceTransformer> itr = transformers.listIterator(transformers.size());
-		while (itr.hasPrevious()) {
-			chain = new DefaultResourceTransformerChain(resolverChain, itr.previous(), chain);
+		ListIterator<? extends ResourceTransformer> it = transformers.listIterator(transformers.size());
+		while (it.hasPrevious()) {
+			chain = new DefaultResourceTransformerChain(resolverChain, it.previous(), chain);
 		}
 		return chain;
 	}
@@ -73,23 +72,22 @@ class DefaultResourceTransformerChain implements ResourceTransformerChain {
 
 		Assert.isTrue((transformer == null && chain == null) || (transformer != null && chain != null),
 				"Both transformer and transformer chain must be null, or neither is");
-
 		this.resolverChain = resolverChain;
 		this.transformer = transformer;
 		this.nextChain = chain;
 	}
 
+
+	@Override
 	public ResourceResolverChain getResolverChain() {
 		return this.resolverChain;
 	}
 
-
 	@Override
-	@SuppressWarnings("ConstantConditions")
 	public Mono<Resource> transform(ServerWebExchange exchange, Resource resource) {
-		return this.transformer != null ?
+		return (this.transformer != null && this.nextChain != null ?
 				this.transformer.transform(exchange, resource, this.nextChain) :
-				Mono.just(resource);
+				Mono.just(resource));
 	}
 
-}
+}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/RequestPartMethodArgumentResolverTests.java

@@ -249,9 +249,7 @@ public class RequestPartMethodArgumentResolverTests {
 		return (T) value;
 	}
 
-	@SuppressWarnings("ConstantConditions")
 	private ServerWebExchange createExchange(MultipartBodyBuilder builder) {
-
 		MockClientHttpRequest clientRequest = new MockClientHttpRequest(HttpMethod.POST, "/");
 		this.writer.write(Mono.just(builder.build()), forClass(MultiValueMap.class),
 				MediaType.MULTIPART_FORM_DATA, clientRequest, Collections.emptyMap()).block();

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/ResponseEntityResultHandlerTests.java

@@ -56,16 +56,13 @@ import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-import static org.springframework.core.ResolvableType.forClassWithGenerics;
-import static org.springframework.http.MediaType.APPLICATION_JSON;
-import static org.springframework.http.ResponseEntity.notFound;
-import static org.springframework.http.ResponseEntity.ok;
-import static org.springframework.mock.http.server.reactive.test.MockServerHttpRequest.get;
-import static org.springframework.web.method.ResolvableMethod.on;
-import static org.springframework.web.reactive.HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE;
+import static org.junit.Assert.*;
+import static org.springframework.core.ResolvableType.*;
+import static org.springframework.http.MediaType.*;
+import static org.springframework.http.ResponseEntity.*;
+import static org.springframework.mock.http.server.reactive.test.MockServerHttpRequest.*;
+import static org.springframework.web.method.ResolvableMethod.*;
+import static org.springframework.web.reactive.HandlerMapping.*;
 
 /**
  * Unit tests for {@link ResponseEntityResultHandler}. When adding a test also
@@ -106,9 +103,7 @@ public class ResponseEntityResultHandlerTests {
 
 
 	@Test
-	@SuppressWarnings("ConstantConditions")
-	public void supports() throws NoSuchMethodException {
-
+	public void supports() throws Exception {
 		Object value = null;
 
 		MethodParameter returnType = on(TestController.class).resolveReturnType(entity(String.class));
@@ -133,9 +128,7 @@ public class ResponseEntityResultHandlerTests {
 	}
 
 	@Test
-	@SuppressWarnings("ConstantConditions")
-	public void doesNotSupport() throws NoSuchMethodException {
-
+	public void doesNotSupport() throws Exception {
 		Object value = null;
 
 		MethodParameter returnType = on(TestController.class).resolveReturnType(String.class);
@@ -417,7 +410,6 @@ public class ResponseEntityResultHandlerTests {
 		Flux<?> fluxWildcard() { return null; }
 
 		Object object() { return null; }
-
 	}
 
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/DefaultResourceResolverChain.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,7 +42,7 @@ class DefaultResourceResolverChain implements ResourceResolverChain {
 
 
 	public DefaultResourceResolverChain(@Nullable List<? extends ResourceResolver> resolvers) {
-		resolvers = resolvers != null ? resolvers : Collections.emptyList();
+		resolvers = (resolvers != null ? resolvers : Collections.emptyList());
 		DefaultResourceResolverChain chain = initChain(new ArrayList<>(resolvers));
 		this.resolver = chain.resolver;
 		this.nextChain = chain.nextChain;
@@ -50,19 +50,16 @@ class DefaultResourceResolverChain implements ResourceResolverChain {
 
 	private static DefaultResourceResolverChain initChain(ArrayList<? extends ResourceResolver> resolvers) {
 		DefaultResourceResolverChain chain = new DefaultResourceResolverChain(null, null);
-		ListIterator<? extends ResourceResolver> itr = resolvers.listIterator(resolvers.size());
-		while (itr.hasPrevious()) {
-			chain = new DefaultResourceResolverChain(itr.previous(), chain);
+		ListIterator<? extends ResourceResolver> it = resolvers.listIterator(resolvers.size());
+		while (it.hasPrevious()) {
+			chain = new DefaultResourceResolverChain(it.previous(), chain);
 		}
 		return chain;
 	}
 
-	private DefaultResourceResolverChain(@Nullable ResourceResolver resolver,
-			@Nullable ResourceResolverChain chain) {
-
+	private DefaultResourceResolverChain(@Nullable ResourceResolver resolver, @Nullable ResourceResolverChain chain) {
 		Assert.isTrue((resolver == null && chain == null) || (resolver != null && chain != null),
 				"Both resolver and resolver chain must be null, or neither is");
-
 		this.resolver = resolver;
 		this.nextChain = chain;
 	}
@@ -70,20 +67,18 @@ class DefaultResourceResolverChain implements ResourceResolverChain {
 
 	@Override
 	@Nullable
-	@SuppressWarnings("ConstantConditions")
-	public Resource resolveResource(@Nullable HttpServletRequest request, String requestPath,
-			List<? extends Resource> locations) {
+	public Resource resolveResource(
+			@Nullable HttpServletRequest request, String requestPath, List<? extends Resource> locations) {
 
-		return this.resolver != null ?
-				this.resolver.resolveResource(request, requestPath, locations, this.nextChain) : null;
+		return (this.resolver != null && this.nextChain != null ?
+				this.resolver.resolveResource(request, requestPath, locations, this.nextChain) : null);
 	}
 
 	@Override
 	@Nullable
-	@SuppressWarnings("ConstantConditions")
 	public String resolveUrlPath(String resourcePath, List<? extends Resource> locations) {
-		return this.resolver != null ?
-				this.resolver.resolveUrlPath(resourcePath, locations, this.nextChain) : null;
+		return (this.resolver != null && this.nextChain != null ?
+				this.resolver.resolveUrlPath(resourcePath, locations, this.nextChain) : null);
 	}
 
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/DefaultResourceTransformerChain.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,13 +44,12 @@ class DefaultResourceTransformerChain implements ResourceTransformerChain {
 	private final ResourceTransformerChain nextChain;
 
 
-	public DefaultResourceTransformerChain(ResourceResolverChain resolverChain,
-			@Nullable List<ResourceTransformer> transformers) {
+	public DefaultResourceTransformerChain(
+			ResourceResolverChain resolverChain, @Nullable List<ResourceTransformer> transformers) {
 
 		Assert.notNull(resolverChain, "ResourceResolverChain is required");
 		this.resolverChain = resolverChain;
-
-		transformers = transformers != null ? transformers : Collections.emptyList();
+		transformers = (transformers != null ? transformers : Collections.emptyList());
 		DefaultResourceTransformerChain chain = initTransformerChain(resolverChain, new ArrayList<>(transformers));
 		this.transformer = chain.transformer;
 		this.nextChain = chain.nextChain;
@@ -60,9 +59,9 @@ class DefaultResourceTransformerChain implements ResourceTransformerChain {
 			ArrayList<ResourceTransformer> transformers) {
 
 		DefaultResourceTransformerChain chain = new DefaultResourceTransformerChain(resolverChain, null, null);
-		ListIterator<? extends ResourceTransformer> itr = transformers.listIterator(transformers.size());
-		while (itr.hasPrevious()) {
-			chain = new DefaultResourceTransformerChain(resolverChain, itr.previous(), chain);
+		ListIterator<? extends ResourceTransformer> it = transformers.listIterator(transformers.size());
+		while (it.hasPrevious()) {
+			chain = new DefaultResourceTransformerChain(resolverChain, it.previous(), chain);
 		}
 		return chain;
 	}
@@ -83,12 +82,10 @@ class DefaultResourceTransformerChain implements ResourceTransformerChain {
 		return this.resolverChain;
 	}
 
-
 	@Override
-	@SuppressWarnings("ConstantConditions")
 	public Resource transform(HttpServletRequest request, Resource resource) throws IOException {
-		return transformer != null ?
-				this.transformer.transform(request, resource, this.nextChain) : resource;
+		return (this.transformer != null && this.nextChain != null ?
+				this.transformer.transform(request, resource, this.nextChain) : resource);
 	}
 
 }

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolverTests.java

@@ -94,7 +94,6 @@ public class ExceptionHandlerExceptionResolverTests {
 
 
 	@Test
-	@SuppressWarnings("ConstantConditions")
 	public void nullHandler() {
 		Object handler = null;
 		this.resolver.afterPropertiesSet();
@@ -103,7 +102,7 @@ public class ExceptionHandlerExceptionResolverTests {
 	}
 
 	@Test
-	public void setCustomArgumentResolvers() throws Exception {
+	public void setCustomArgumentResolvers() {
 		HandlerMethodArgumentResolver resolver = new ServletRequestMethodArgumentResolver();
 		this.resolver.setCustomArgumentResolvers(Collections.singletonList(resolver));
 		this.resolver.afterPropertiesSet();
@@ -113,7 +112,7 @@ public class ExceptionHandlerExceptionResolverTests {
 	}
 
 	@Test
-	public void setArgumentResolvers() throws Exception {
+	public void setArgumentResolvers() {
 		HandlerMethodArgumentResolver resolver = new ServletRequestMethodArgumentResolver();
 		this.resolver.setArgumentResolvers(Collections.singletonList(resolver));
 		this.resolver.afterPropertiesSet();