feat: Microservices pattern : Self-Registration (#3245)

* Services and information

* README.md updated

* unit tests added for controllers

* pom.xml, clean up, java version update and slf4j logging added

* pom files updated

* Removed children maven wrappers

* Microservice-self-registration added to pom file

* POM file updated for self-registration

* pom file updated

* Update pom.xml

correction to mudule name

* SonarQube comments addressed

* sonarqube comments on coverage addressed

* Code coverage for custom health checks

* changes for unit tests

* changes for unit tests

* changes to for code coverage improvement

microservices-self-registration/greetingservice/.gitattributes

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+/mvnw text eol=lf
+*.cmd text eol=crlf

microservices-self-registration/greetingservice/.gitignore

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+HELP.md
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/

microservices-self-registration/greetingservice/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>3.4.4</version>
+        <relativePath/> </parent>
+    <groupId>com.learning</groupId>
+    <artifactId>greetingservice</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>greetingservice</name>
+    <description>greetingservice</description>
+
+    <properties>
+        <spring-cloud.version>2024.0.1</spring-cloud.version>
+    </properties>
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>1.18.38</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.cloud</groupId>
+            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-actuator</artifactId>
+        </dependency>
+     </dependencies>
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.springframework.cloud</groupId>
+                <artifactId>spring-cloud-dependencies</artifactId>
+                <version>${spring-cloud.version}</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

microservices-self-registration/greetingservice/src/main/java/com/learning/greetingservice/GreetingserviceApplication.java

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+package com.learning.greetingservice;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
+import org.springframework.context.annotation.ComponentScan;
+
+@SpringBootApplication
+@EnableDiscoveryClient
+@ComponentScan("com.learning.greetingservice.controller")
+public class GreetingserviceApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(GreetingserviceApplication.class, args);
+	}
+
+}

microservices-self-registration/greetingservice/src/main/java/com/learning/greetingservice/MyCustomHealthCheck.java

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+package com.learning.greetingservice;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.HealthIndicator;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+@Component("myCustomHealthCheck")
+public class MyCustomHealthCheck implements HealthIndicator {
+
+  private static final Logger log = LoggerFactory.getLogger(MyCustomHealthCheck.class);
+
+  private volatile boolean isHealthy = true;
+
+  @Scheduled(fixedRate = 5000) // Run every 5 seconds
+  public void updateHealthStatus() {
+    // Perform checks here to determine the current health
+    // For example, check database connectivity, external service availability, etc.
+    isHealthy = performHealthCheck();
+    log.info("Update health status : {}", isHealthy);
+  }
+
+  boolean performHealthCheck() {
+    boolean current = System.currentTimeMillis() % 10000 < 5000; // Simulate fluctuating health
+    log.debug("Performing health check, current status: {}", current);
+    return current; // Simulate fluctuating health
+  }
+
+  @Override
+  public Health health() {
+    if (isHealthy) {
+      log.info("Health check successful, service is UP");
+      return Health.up().withDetail("message", "Service is running and scheduled checks are OK").build();
+    } else {
+      log.warn("Health check failed, service is DOWN");
+      return Health.down().withDetail("error", "Scheduled health checks failed").build();
+    }
+  }
+}

microservices-self-registration/greetingservice/src/main/java/com/learning/greetingservice/controller/GreetingsController.java

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+package com.learning.greetingservice.controller;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class GreetingsController {
+
+  @GetMapping("/greeting")
+  public String getGreeting() {
+    return "Hello";
+  }
+}

microservices-self-registration/greetingservice/src/main/resources/application.yml

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+server:
+    port: 8081
+
+spring:
+    application:
+        name: greetingservice
+eureka:
+  client:
+      service-url.defaultZone: http://localhost:8761/eureka
+
+management:
+  endpoint:
+    health:
+        show-details: always
+    web:
+      exposure:
+          include: health
+
+logging:
+    file:
+        name: application.log
+

microservices-self-registration/greetingservice/src/test/java/com/learning/greetingservice/GreetingserviceApplicationTests.java

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+package com.learning.greetingservice;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class GreetingserviceApplicationTests {
+
+	@Test
+	void contextLoads() {
+    // This is a basic integration test that checks if the Spring Application Context loads successfully.
+    // If the context loads without any exceptions, the test is considered passing.
+    // It is often left empty as the act of loading the context is the primary verification.
+    // You can add specific assertions here if you want to verify the presence or state of certain beans.
+	}
+
+}

microservices-self-registration/greetingservice/src/test/java/com/learning/greetingservice/MyCustomHealthCheckTest.java

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+package com.learning.greetingservice;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.actuate.health.Health;
+import org.springframework.test.util.ReflectionTestUtils;
+import org.springframework.boot.actuate.health.Status;
+import static org.junit.jupiter.api.Assertions.*;
+
+class MyCustomHealthCheckTest {
+
+  @Test
+  void testHealthUp() {
+    MyCustomHealthCheck healthCheck = new MyCustomHealthCheck();
+    // Simulate a healthy state
+    ReflectionTestUtils.setField(healthCheck, "isHealthy", true);
+    Health health = healthCheck.health();
+    assertEquals(Status.UP, health.getStatus());
+    assertTrue(health.getDetails().containsKey("message"));
+    assertEquals("Service is running and scheduled checks are OK", health.getDetails().get("message"));
+  }
+
+}

microservices-self-registration/greetingservice/src/test/java/com/learning/greetingservice/controller/GreetingControllerTest.java

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+package com.learning.greetingservice.controller;
+
+import com.learning.greetingservice.GreetingserviceApplication;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.http.MediaType;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
+import org.springframework.test.web.servlet.result.MockMvcResultMatchers;
+
+@SpringBootTest(classes = GreetingserviceApplication.class)
+@AutoConfigureMockMvc
+@ActiveProfiles("test")
+class GreetingControllerTest {
+
+  @Autowired
+  private MockMvc mockMvc;
+
+  @Test
+  void shouldReturnGreeting() throws Exception{
+    mockMvc.perform(MockMvcRequestBuilders.get("/greeting")
+            .accept(MediaType.TEXT_PLAIN))
+        .andExpect(MockMvcResultMatchers.status().isOk())
+        .andExpect(MockMvcResultMatchers.content().string("Hello"));
+  }
+
+  @Test
+  void shouldReturnHealthStatusUp() throws Exception{
+    mockMvc.perform(MockMvcRequestBuilders.get("/actuator/health"))
+        .andExpect(MockMvcResultMatchers.status().isOk())
+        .andExpect(MockMvcResultMatchers.content().string(org.hamcrest.Matchers.containsString("\"status\":\"UP\"")));
+  }
+}