Add the sse-websocket module

2026-09-04 00:52:18 +05:30
parent e1f8aa7402
commit 5224afdad2
51 changed files with 2761 additions and 0 deletions
--- a/sse-websocket/src/test/java/com/ankurm/ssews/SseDataConversionTest.java
+++ b/sse-websocket/src/test/java/com/ankurm/ssews/SseDataConversionTest.java
@@ -0,0 +1,70 @@
+package com.ankurm.ssews;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.server.LocalServerPort;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * {@code .data(object)} and {@code .data(object, APPLICATION_JSON)} are not the same call.
+ * This test prints both results side by side.
+ */
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT,
+        properties = "dashboard.broadcast.enabled=false")
+class SseDataConversionTest {
+
+    @LocalServerPort
+    int port;
+
+    @Test
+    void mediaTypeDecidesTheConverter() throws Exception {
+        List<String> lines;
+        try (SseClient client = new SseClient(port, "/sse/payload")) {
+            lines = client.readToEnd();
+        }
+
+        String withJson = dataAfter(lines, "event:with-json");
+        String noMediaType = dataAfter(lines, "event:no-media-type");
+
+        System.out.println("=== SseEmitter.event().data(record, APPLICATION_JSON) ===");
+        System.out.println(withJson);
+        System.out.println("=== SseEmitter.event().data(record)  [no media type] ===");
+        System.out.println(noMediaType);
+
+        assertThat(withJson).startsWith("{").contains("\"seq\":7").contains("\"host\":\"node-a\"");
+
+        // The finding: for a POJO they are IDENTICAL. No media type does not mean toString().
+        // send() asks the configured HttpMessageConverters which one canWrite(type, null), and
+        // for a record the first (and only) answer is the Jackson converter.
+        System.out.println("=== POJO: identical? " + withJson.equals(noMediaType) + " ===");
+        assertThat(noMediaType).isEqualTo(withJson);
+
+        String stringPlain = dataAfter(lines, "event:string-plain");
+        String stringJson = dataAfter(lines, "event:string-json");
+        System.out.println("=== String payload, no media type   -> " + stringPlain);
+        System.out.println("=== String payload, APPLICATION_JSON -> " + stringJson);
+
+        // The finding, and it is the opposite of what I expected when writing this test: for a
+        // String the media type argument changes NOTHING. StringHttpMessageConverter supports
+        // MediaType.ALL and sits ahead of the Jackson converter in the list, so it claims the
+        // write even when you ask for application/json. There is no way to make send() quote a
+        // String -- which is good news if you are streaming pre-rendered JSON, and a trap if you
+        // expected a String field to be escaped for you.
+        assertThat(stringPlain).isEqualTo("{\"already\":\"json\"}");
+        assertThat(stringJson).isEqualTo(stringPlain);
+    }
+
+    private static String dataAfter(List<String> lines, String eventLine) {
+        int i = lines.indexOf(eventLine);
+        assertThat(i).as("event line %s present", eventLine).isGreaterThanOrEqualTo(0);
+        for (int j = i; j < lines.size(); j++) {
+            if (lines.get(j).startsWith("data:")) {
+                return lines.get(j).substring("data:".length());
+            }
+        }
+        throw new AssertionError("no data line after " + eventLine);
+    }
+}