Add the sse-websocket module

sse-websocket/src/main/java/com/ankurm/ssews/WebSocketBufferConfig.java

@@ -0,0 +1,35 @@
+package com.ankurm.ssews;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Profile;
+import org.springframework.web.socket.server.standard.ServletServerContainerFactoryBean;
+
+/**
+ * The other half of the message size limit — the half that is not in Spring.
+ *
+ * <p>{@code WebSocketTransportRegistration.setMessageSizeLimit(64 * 1024)} is not the limit that
+ * bites first. Spring's {@code SubProtocolWebSocketHandler} does not support partial messages,
+ * so the servlet container has to buffer each WebSocket text message whole before handing it
+ * over &mdash; and Tomcat's buffer defaults to <strong>8&nbsp;192 bytes</strong>. Cross that and
+ * Tomcat closes the connection with WebSocket status <strong>1009</strong> before Spring ever
+ * sees the frame, so raising Spring's limit alone changes nothing.
+ *
+ * <p>Active under the {@code bigframes} profile so the companion test can show both behaviours
+ * from one build.
+ *
+ * @see <a href="../../../../../docs/05-limits.md">docs/05-limits.md</a>
+ */
+@Configuration
+@Profile("bigframes")
+public class WebSocketBufferConfig {
+
+    @Bean
+    public ServletServerContainerFactoryBean createWebSocketContainer(
+            @org.springframework.beans.factory.annotation.Value("${ws.buffer-bytes:262144}") int bytes) {
+        ServletServerContainerFactoryBean container = new ServletServerContainerFactoryBean();
+        container.setMaxTextMessageBufferSize(bytes);
+        container.setMaxBinaryMessageBufferSize(bytes);
+        return container;
+    }
+}