Make getters and setters null-safety consistent

This commit ensure that null-safety is consistent between
getters and setters in order to be able to provide beans
with properties with a common type when type safety is
taken in account like with Kotlin.

It also add a few missing property level @Nullable
annotations.

Issue: SPR-15792

spring-websocket/src/main/java/org/springframework/web/socket/WebSocketHttpHeaders.java

@@ -87,7 +87,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * Sets the (new) value of the {@code Sec-WebSocket-Accept} header.
 	 * @param secWebSocketAccept the value of the header
 	 */
-	public void setSecWebSocketAccept(String secWebSocketAccept) {
+	public void setSecWebSocketAccept(@Nullable String secWebSocketAccept) {
 		set(SEC_WEBSOCKET_ACCEPT, secWebSocketAccept);
 	}
 
@@ -134,7 +134,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * Sets the (new) value of the {@code Sec-WebSocket-Key} header.
 	 * @param secWebSocketKey the value of the header
 	 */
-	public void setSecWebSocketKey(String secWebSocketKey) {
+	public void setSecWebSocketKey(@Nullable String secWebSocketKey) {
 		set(SEC_WEBSOCKET_KEY, secWebSocketKey);
 	}
 
@@ -184,7 +184,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * Sets the (new) value of the {@code Sec-WebSocket-Version} header.
 	 * @param secWebSocketVersion the value of the header
 	 */
-	public void setSecWebSocketVersion(String secWebSocketVersion) {
+	public void setSecWebSocketVersion(@Nullable String secWebSocketVersion) {
 		set(SEC_WEBSOCKET_VERSION, secWebSocketVersion);
 	}
 
@@ -232,7 +232,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * @see #add(String, String)
 	 */
 	@Override
-	public void set(String headerName, String headerValue) {
+	public void set(String headerName, @Nullable String headerValue) {
 		this.headers.set(headerName, headerValue);
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/client/WebSocketConnectionManager.java

@@ -86,7 +86,7 @@ public class WebSocketConnectionManager extends ConnectionManagerSupport {
 	/**
 	 * Set the origin to use.
 	 */
-	public void setOrigin(String origin) {
+	public void setOrigin(@Nullable String origin) {
 		this.headers.setOrigin(origin);
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/AbstractWebSocketHandlerRegistration.java

@@ -84,7 +84,7 @@ public abstract class AbstractWebSocketHandlerRegistration<M> implements WebSock
 	}
 
 	@Override
-	public WebSocketHandlerRegistration setHandshakeHandler(HandshakeHandler handshakeHandler) {
+	public WebSocketHandlerRegistration setHandshakeHandler(@Nullable HandshakeHandler handshakeHandler) {
 		this.handshakeHandler = handshakeHandler;
 		return this;
 	}

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/ServletWebSocketHandlerRegistry.java

@@ -92,7 +92,7 @@ public class ServletWebSocketHandlerRegistry implements WebSocketHandlerRegistry
 	 * Set the UrlPathHelper to configure on the {@code SimpleUrlHandlerMapping}
 	 * used to map handshake requests.
 	 */
-	public void setUrlPathHelper(UrlPathHelper urlPathHelper) {
+	public void setUrlPathHelper(@Nullable UrlPathHelper urlPathHelper) {
 		this.urlPathHelper = urlPathHelper;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebMvcStompEndpointRegistry.java

@@ -125,7 +125,7 @@ public class WebMvcStompEndpointRegistry implements StompEndpointRegistry {
 	 * used to map handshake requests.
 	 */
 	@Override
-	public void setUrlPathHelper(UrlPathHelper urlPathHelper) {
+	public void setUrlPathHelper(@Nullable UrlPathHelper urlPathHelper) {
 		this.urlPathHelper = urlPathHelper;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/messaging/StompSubProtocolHandler.java

@@ -176,7 +176,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 	 * client inbound channel.
 	 * <p>By default this property is not set.
 	 */
-	public void setHeaderInitializer(MessageHeaderInitializer headerInitializer) {
+	public void setHeaderInitializer(@Nullable MessageHeaderInitializer headerInitializer) {
 		this.headerInitializer = headerInitializer;
 		this.stompDecoder.setHeaderInitializer(headerInitializer);
 	}

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SubProtocolWebSocketHandler.java

@@ -172,7 +172,7 @@ public class SubProtocolWebSocketHandler
 	 * sub-protocol.
 	 * @param defaultProtocolHandler the default handler
 	 */
-	public void setDefaultProtocolHandler(SubProtocolHandler defaultProtocolHandler) {
+	public void setDefaultProtocolHandler(@Nullable SubProtocolHandler defaultProtocolHandler) {
 		this.defaultProtocolHandler = defaultProtocolHandler;
 		if (this.protocolHandlerLookup.isEmpty()) {
 			setProtocolHandlers(Collections.singletonList(defaultProtocolHandler));

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/ServerEndpointExporter.java

@@ -76,7 +76,7 @@ public class ServerEndpointExporter extends WebApplicationObjectSupport
 	 * Set the JSR-356 {@link ServerContainer} to use for endpoint registration.
 	 * If not set, the container is going to be retrieved via the {@code ServletContext}.
 	 */
-	public void setServerContainer(ServerContainer serverContainer) {
+	public void setServerContainer(@Nullable ServerContainer serverContainer) {
 		this.serverContainer = serverContainer;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/SockJsClient.java

@@ -134,7 +134,7 @@ public class SockJsClient implements WebSocketClient, Lifecycle {
 	 *
 	 * @param httpHeaderNames HTTP header names
 	 */
-	public void setHttpHeaderNames(String... httpHeaderNames) {
+	public void setHttpHeaderNames(@Nullable String... httpHeaderNames) {
 		this.httpHeaderNames = httpHeaderNames;
 	}