[BAEL-7412] Add code for running multiple tomcat instances

server-modules/apache-tomcat-2/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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>server-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>apache-tomcat-2</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.tomcat</groupId>
+            <artifactId>tomcat-catalina</artifactId>
+            <version>${tomcat.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.tomcat</groupId>
+            <artifactId>tomcat-juli</artifactId>
+            <version>${tomcat.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>jakarta.servlet</groupId>
+            <artifactId>jakarta.servlet-api</artifactId>
+            <version>6.0.0</version>
+        </dependency>
+
+        <!-- Test Dependencies -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.10.0</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.11.0</version>
+                <configuration>
+                    <source>11</source>
+                    <target>11</target>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.0.0</version>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <tomcat.version>10.1.24</tomcat.version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

server-modules/apache-tomcat-2/src/main/java/com/baeldung/tomcat/AppServerXML.java

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+package com.baeldung.tomcat;
+
+import org.apache.catalina.startup.Catalina;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.file.*;
+
+public class AppServerXML {
+
+    public static void main(String[] args) throws Exception {
+        AppServerXML app = new AppServerXML();
+        Catalina catalina = app.startServer();
+        catalina.getServer().await();
+    }
+
+    public Catalina startServer() throws Exception {
+        URL staticUrl = getClass().getClassLoader().getResource("static");
+        if (staticUrl == null) {
+            throw new IllegalStateException("Static directory not found in classpath");
+        }
+        Path staticDir = Paths.get(staticUrl.toURI());
+
+        Path baseDir = Paths.get("target/tomcat-base").toAbsolutePath();
+        Files.createDirectories(baseDir);
+
+        String config;
+        try (InputStream serverXmlStream = getClass().getClassLoader().getResourceAsStream("server.xml")) {
+            if (serverXmlStream == null) {
+                throw new IllegalStateException("server.xml not found in classpath");
+            }
+            config = new String(serverXmlStream.readAllBytes())
+                    .replace("STATIC_DIR_PLACEHOLDER", staticDir.toString());
+        }
+
+        Path configFile = baseDir.resolve("server.xml");
+        Files.writeString(configFile, config);
+
+        System.setProperty("catalina.base", baseDir.toString());
+        System.setProperty("catalina.home", baseDir.toString());
+
+        Catalina catalina = new Catalina();
+        catalina.load(new String[]{"-config", configFile.toString()});
+        catalina.start();
+
+        System.out.println("\nTomcat started with multiple connectors!");
+        System.out.println("http://localhost:8081");
+        System.out.println("http://localhost:7081");
+
+        return catalina;
+    }
+}

server-modules/apache-tomcat-2/src/main/java/com/baeldung/tomcat/DualPort.java

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+package com.baeldung.tomcat;
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.apache.catalina.connector.Connector;
+import java.io.File;
+import java.io.IOException;
+
+import org.apache.catalina.Context;
+import org.apache.catalina.startup.Tomcat;
+
+public class DualPort {
+
+    public static void main(String[] args) throws Exception {
+        DualPort dualPort = new DualPort();
+        Tomcat tomcat = dualPort.startServer();
+        tomcat.getServer().await();
+    }
+
+    public Tomcat startServer() throws Exception {
+        Tomcat tomcat = new Tomcat();
+        tomcat.setBaseDir(new File("tomcat-temp").getAbsolutePath());
+
+        tomcat.setPort(7080);
+        tomcat.getConnector();
+
+        Connector secondConnector = new Connector();
+        secondConnector.setPort(8080);
+        tomcat.getService().addConnector(secondConnector);
+
+        Context ctx = tomcat.addContext("", new File(".").getAbsolutePath());
+        Tomcat.addServlet(ctx, "portServlet", new HttpServlet() {
+            @Override
+            protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+                int port = req.getLocalPort();
+                resp.setContentType("text/plain");
+                resp.getWriter().write("Port: " + port + "\n");
+            }
+        });
+        ctx.addServletMappingDecoded("/", "portServlet");
+
+        tomcat.start();
+        System.out.println("Tomcat running on ports 8080 and 7080");
+
+        return tomcat;
+    }
+}

server-modules/apache-tomcat-2/src/main/java/com/baeldung/tomcat/PortServlet.java

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+package com.baeldung.tomcat;
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+public class PortServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+        int port = req.getLocalPort();
+        resp.setContentType("text/plain");
+        resp.getWriter().write("port number: " + port);
+    }
+}

server-modules/apache-tomcat-2/src/main/resources/server.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<Server port="8005" shutdown="SHUTDOWN">
+    <Service name="Catalina">
+        <Connector port="8081" protocol="HTTP/1.1" />
+        <Connector port="7081" protocol="HTTP/1.1" />
+
+        <Engine name="Catalina" defaultHost="localhost">
+            <Host name="localhost" appBase="/tmp/tomcat-dummy" unpackWARs="false" autoDeploy="false">
+                <Context path="" docBase="STATIC_DIR_PLACEHOLDER" reloadable="false" />
+            </Host>
+        </Engine>
+    </Service>
+</Server>

server-modules/apache-tomcat-2/src/main/resources/static/WEB-INF/web.xml

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee
+         https://jakarta.ee/xml/ns/jakartaee/web-app_6_0.xsd"
+         version="6.0">
+
+    <display-name>Static HTML Application</display-name>
+
+    <!-- Default servlet for serving static content -->
+    <servlet>
+        <servlet-name>default</servlet-name>
+        <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
+        <init-param>
+            <param-name>listings</param-name>
+            <param-value>false</param-value>
+        </init-param>
+        <load-on-startup>1</load-on-startup>
+    </servlet>
+
+    <servlet-mapping>
+        <servlet-name>default</servlet-name>
+        <url-pattern>/</url-pattern>
+    </servlet-mapping>
+
+    <!-- Welcome files -->
+    <welcome-file-list>
+        <welcome-file>index.html</welcome-file>
+    </welcome-file-list>
+</web-app>
+

server-modules/apache-tomcat-2/src/main/resources/static/index.html

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+<!DOCTYPE html>
+<html>
+<head><title>Dual Port Test</title></head>
+<body>
+<h1>Tomcat is running!</h1>
+<p>Port: <script>document.write(window.location.port)</script></p>
+</body>
+</html>

server-modules/apache-tomcat-2/src/test/java/com/baeldung/tomcat/AppServerXMLUnitTest.java

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+package com.baeldung.tomcat;
+
+import org.apache.catalina.startup.Catalina;
+import org.junit.jupiter.api.*;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
+public class AppServerXMLUnitTest {
+
+    private static AppServerXML app;
+    private static Catalina catalina;
+    private static final int HTTP_PORT_1 = 8081;
+    private static final int HTTP_PORT_2 = 7081;
+
+    @BeforeAll
+    static void setUp() throws Exception {
+        app = new AppServerXML();
+        catalina = app.startServer();
+        Thread.sleep(2000);
+    }
+
+    @AfterAll
+    static void shutDown() throws Exception {
+        if (catalina != null && catalina.getServer() != null) {
+            catalina.stop();
+            Thread.sleep(1000);
+        }
+    }
+
+    @Test
+    void givenMultipleConnectors_whenServerStarts_thenContainsMultiplePorts() {
+        assertNotNull(catalina.getServer(), "Server should be initialized");
+
+        Path configFile = Paths.get("target/tomcat-base/server.xml");
+        assertTrue(Files.exists(configFile), "Generated server.xml should exist");
+
+        assertDoesNotThrow(() -> {
+            String config = Files.readString(configFile);
+            assertTrue(config.contains("port=\"8081\""), "Config should have port 8081");
+            assertTrue(config.contains("port=\"7081\""), "Config should have port 7081");
+            assertFalse(config.contains("STATIC_DIR_PLACEHOLDER"), "Placeholder should be replaced");
+        });
+    }
+
+    @Test
+    void givenMultipleConnectors_whenResponds_thenReturns200() {
+        assertDoesNotThrow(() -> {
+            int response1 = getResponseCode(HTTP_PORT_1);
+            int response2 = getResponseCode(HTTP_PORT_2);
+
+            assertEquals(200, response1, "Port 8081 should respond with 200 OK");
+            assertEquals(200, response2, "Port 7081 should respond with 200 OK");
+        });
+    }
+
+    @Test
+    void givenMultipleConnectors_whenResponds_thenReturnsIdenticalContent() {
+        assertDoesNotThrow(() -> {
+            String content1 = getContent(HTTP_PORT_1);
+            String content2 = getContent(HTTP_PORT_2);
+
+            assertNotNull(content1, "Content from port 8081 should not be null");
+            assertNotNull(content2, "Content from port 7081 should not be null");
+
+            assertTrue(content1.contains("Tomcat is running"), "Content should contain expected text");
+            assertEquals(content1, content2, "Both ports should serve identical content");
+        });
+    }
+
+    private int getResponseCode(int port) throws Exception {
+        HttpURLConnection connection = getConnection(port);
+        try {
+            return connection.getResponseCode();
+        } finally {
+            connection.disconnect();
+        }
+    }
+
+    private String getContent(int port) throws Exception {
+        HttpURLConnection connection = getConnection(port);
+        try (BufferedReader reader = new BufferedReader(
+                new InputStreamReader(connection.getInputStream()))) {
+            return reader.lines().collect(Collectors.joining());
+        } finally {
+            connection.disconnect();
+        }
+    }
+
+    private HttpURLConnection getConnection(int port) throws IOException {
+        URL url = URI.create("http://localhost:" + port + "/").toURL();
+        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
+        connection.setRequestMethod("GET");
+        connection.setConnectTimeout(5000);
+        connection.setReadTimeout(5000);
+        return connection;
+    }
+}
+