Bael 4149: Liveness and Readiness probes in Spring Boot 2.3 (#9484)

* Added Liveness and Readiness Samples

* Added the Missing Files

spring-boot-modules/spring-boot-actuator/src/main/java/com/baeldung/probes/ProbesApplication.java

@@ -0,0 +1,12 @@
+package com.baeldung.probes;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ProbesApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ProbesApplication.class, args);
+    }
+}

spring-boot-modules/spring-boot-actuator/src/main/resources/application.properties

@@ -0,0 +1 @@
+management.health.probes.enabled=true

spring-boot-modules/spring-boot-actuator/src/test/java/com/baeldung/probes/ApplicationAvailabilityIntegrationTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.probes;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.availability.ApplicationAvailability;
+import org.springframework.boot.availability.AvailabilityChangeEvent;
+import org.springframework.boot.availability.LivenessState;
+import org.springframework.boot.availability.ReadinessState;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.annotation.DirtiesContext.ClassMode.AFTER_CLASS;
+import static org.springframework.test.annotation.DirtiesContext.MethodMode.AFTER_METHOD;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@SpringBootTest
+@AutoConfigureMockMvc
+@DirtiesContext(classMode = AFTER_CLASS)
+public class ApplicationAvailabilityIntegrationTest {
+
+    @Autowired private MockMvc mockMvc;
+    @Autowired private ApplicationContext context;
+    @Autowired private ApplicationAvailability applicationAvailability;
+
+    @Test
+    public void givenApplication_whenStarted_thenShouldBeAbleToRetrieveReadinessAndLiveness() {
+        assertThat(applicationAvailability.getLivenessState()).isEqualTo(LivenessState.CORRECT);
+        assertThat(applicationAvailability.getReadinessState()).isEqualTo(ReadinessState.ACCEPTING_TRAFFIC);
+
+        assertThat(applicationAvailability.getState(ReadinessState.class)).isEqualTo(ReadinessState.ACCEPTING_TRAFFIC);
+    }
+
+    @Test
+    @DirtiesContext(methodMode = AFTER_METHOD)
+    public void givenCorrectState_whenPublishingTheEvent_thenShouldTransitToBrokenState() throws Exception {
+        assertThat(applicationAvailability.getLivenessState()).isEqualTo(LivenessState.CORRECT);
+        mockMvc.perform(get("/actuator/health/liveness"))
+          .andExpect(status().isOk())
+          .andExpect(jsonPath("$.status").value("UP"));
+
+        AvailabilityChangeEvent.publish(context, LivenessState.BROKEN);
+
+        assertThat(applicationAvailability.getLivenessState()).isEqualTo(LivenessState.BROKEN);
+        mockMvc.perform(get("/actuator/health/liveness"))
+          .andExpect(status().isServiceUnavailable())
+          .andExpect(jsonPath("$.status").value("DOWN"));
+    }
+
+    @Test
+    @DirtiesContext(methodMode = AFTER_METHOD)
+    public void givenAcceptingState_whenPublishingTheEvent_thenShouldTransitToRefusingState() throws Exception {
+        assertThat(applicationAvailability.getReadinessState()).isEqualTo(ReadinessState.ACCEPTING_TRAFFIC);
+        mockMvc.perform(get("/actuator/health/readiness"))
+          .andExpect(status().isOk())
+          .andExpect(jsonPath("$.status").value("UP"));
+
+        AvailabilityChangeEvent.publish(context, ReadinessState.REFUSING_TRAFFIC);
+
+        assertThat(applicationAvailability.getReadinessState()).isEqualTo(ReadinessState.REFUSING_TRAFFIC);
+        mockMvc.perform(get("/actuator/health/readiness"))
+          .andExpect(status().isServiceUnavailable())
+          .andExpect(jsonPath("$.status").value("OUT_OF_SERVICE"));
+    }
+}

spring-boot-modules/spring-boot-actuator/src/test/java/com/baeldung/probes/LivenessEventListener.java

@@ -0,0 +1,19 @@
+package com.baeldung.probes;
+
+import org.springframework.boot.availability.AvailabilityChangeEvent;
+import org.springframework.boot.availability.LivenessState;
+import org.springframework.context.event.EventListener;
+
+public class LivenessEventListener {
+
+    @EventListener
+    public void onEvent(AvailabilityChangeEvent<LivenessState> event) {
+        switch (event.getState()) {
+        case BROKEN:
+            // notify others
+            break;
+        case CORRECT:
+            // we're back
+        }
+    }
+}