Add cqrs module: CQRS in Spring Boot Without a Framework

Separate write/read DataSources, a JPA command side, and two interchangeable projection listeners (sync and @Async) demonstrating the real latency-versus- freshness trade-off CQRS forces. Includes a reflection-based proof that the query side has no dependency on the write side, and a real failure/fix transcript for the -parameters compiler flag this standalone reactor doesn't inherit from spring-boot-starter-parent.
2026-10-03 20:59:55 +00:00
parent d815a37f2e
commit b4a623b889
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+package com.ankurm.cqrsdemo;
+
+import com.ankurm.cqrsdemo.command.OrderCommandController.LineRequest;
+import com.ankurm.cqrsdemo.command.OrderCommandController.PlaceOrderRequest;
+import com.ankurm.cqrsdemo.command.OrderCommandController.PlaceOrderResponse;
+import com.ankurm.cqrsdemo.query.OrderSummary;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.resttestclient.autoconfigure.AutoConfigureTestRestTemplate;
+import org.springframework.boot.resttestclient.TestRestTemplate;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.http.ResponseEntity;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Default profile: no {@code async-projection}, so {@link com.ankurm.cqrsdemo.read.SyncOrderSummaryProjection}
+ * is active. The projection's simulated write delay (300ms, see {@code application.properties})
+ * runs on the same thread that is about to answer the command's HTTP request, so it shows up
+ * directly in how long {@code POST /orders} takes -- and because of that, the read model is
+ * already correct the instant the command returns, with no waiting required.
+ */
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+@AutoConfigureTestRestTemplate
+class SyncProfileLatencyTest {
+
+    @org.springframework.beans.factory.annotation.Autowired
+    private TestRestTemplate rest;
+
+    @Test
+    void placingAnOrderTakesAtLeastTheSimulatedProjectionDelayAndTheReadModelIsImmediatelyConsistent() {
+        PlaceOrderRequest request = new PlaceOrderRequest("Priya",
+                List.of(new LineRequest("USB-C-CABLE", 2, 1299), new LineRequest("USB-C-HUB", 1, 4999)));
+
+        long start = System.currentTimeMillis();
+        ResponseEntity<PlaceOrderResponse> placed = rest.postForEntity("/orders", request, PlaceOrderResponse.class);
+        long elapsedMs = System.currentTimeMillis() - start;
+
+        String orderId = placed.getBody().orderId();
+        System.out.println("POST /orders (sync profile) took " + elapsedMs + " ms, orderId=" + orderId);
+        assertThat(elapsedMs).isGreaterThanOrEqualTo(300L);
+
+        ResponseEntity<OrderSummary> summary = rest.getForEntity("/order-summaries/" + orderId, OrderSummary.class);
+        System.out.println("Immediately after POST returned, GET /order-summaries/" + orderId
+                + " -> status=" + summary.getStatusCode() + ", body=" + summary.getBody());
+        assertThat(summary.getBody()).isNotNull();
+        assertThat(summary.getBody().totalCents()).isEqualTo(2 * 1299 + 4999);
+        assertThat(summary.getBody().status()).isEqualTo("PLACED");
+    }
+}