[BAEL-4612] get spring boot port at runtime

spring-boot-modules/spring-boot-environment/src/main/java/com/baeldung/serverport/GetServerPortApplication.java

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

spring-boot-modules/spring-boot-environment/src/main/java/com/baeldung/serverport/ServerPortService.java

@@ -0,0 +1,20 @@
+package com.baeldung.serverport;
+
+import org.springframework.boot.web.servlet.context.ServletWebServerInitializedEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Service;
+
+@Service
+public class ServerPortService {
+    private int port;
+
+    public int getPort() {
+        return port;
+    }
+
+    @EventListener
+    public void onApplicationEvent(final ServletWebServerInitializedEvent event) {
+        port = event.getWebServer().getPort();
+    }
+
+}

spring-boot-modules/spring-boot-environment/src/test/java/com/baeldung/serverport/GetServerFixedPortUnitTest.java

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+package com.baeldung.serverport;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.web.ServerProperties;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = GetServerPortApplication.class, webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)
+@ActiveProfiles("fixedport")
+public class GetServerFixedPortUnitTest {
+    private final static int EXPECTED_PORT = 7777;
+
+    @Value("${server.port}")
+    private int serverPort;
+
+    @Autowired
+    private ServerProperties serverProperties;
+
+    @Test
+    public void givenFixedPortAsServerPort_whenReadServerPort_thenGetThePort() {
+        assertEquals("Reading fixed port by @Value(\"${server.port}\") will get the port.", EXPECTED_PORT, serverPort);
+    }
+
+    @Test
+    public void givenFixedPortAsServerPort_whenReadServerProps_thenGetThePort() {
+        int port = serverProperties.getPort();
+        assertEquals("Reading fixed port from serverProperties will get the port.", EXPECTED_PORT, port);
+    }
+
+}

spring-boot-modules/spring-boot-environment/src/test/java/com/baeldung/serverport/GetServerRandomPortUnitTest.java

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+package com.baeldung.serverport;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.web.ServerProperties;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = GetServerPortApplication.class, webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)
+@ActiveProfiles("randomport")
+public class GetServerRandomPortUnitTest {
+
+    @Value("${server.port}")
+    private int randomServerPort;
+
+    @Autowired
+    private ServerPortService serverPortService;
+
+    @Autowired
+    private ServerProperties serverProperties;
+
+    @Autowired
+    private ServletWebServerApplicationContext webServerAppCtxt;
+
+    @Test
+    public void given0AsServerPort_whenReadServerPort_thenGet0() {
+        assertEquals("Reading random port by @Value(\"${server.port}\") will get 0.", 0, randomServerPort);
+    }
+
+    @Test
+    public void given0AsServerPort_whenReadServerProps_thenGet0() {
+        int port = serverProperties.getPort();
+        assertEquals("Reading random port by serverProperties will get 0.", 0, port);
+    }
+
+    @Test
+    public void given0AsServerPort_whenReadWebAppCtxt_thenGetThePort() {
+        int port = webServerAppCtxt.getWebServer().getPort();
+        assertTrue("The random port should be greater than 1023", port > 1023);
+    }
+
+    @Test
+    public void given0AsServerPort_whenReadFromListener_thenGetThePort() {
+        int port = serverPortService.getPort();
+        assertTrue("The random port should be greater than 1023", port > 1023);
+    }
+}

spring-boot-modules/spring-boot-environment/src/test/resources/application-fixedport.properties

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+server.port=7777

spring-boot-modules/spring-boot-environment/src/test/resources/application-randomport.properties

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+server.port=0