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Java - example HTTP Servlet (Embedded Tomcat Server run from source code)
5
points
In this article, we want to show how to run pure HTTP Servlet (Embedded Tomcat Server) in Java.
Project structure
Project files
src/com/example/DemoApplication.java file:
package com.example;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import org.apache.catalina.Context;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.Server;
import org.apache.catalina.Service;
import org.apache.catalina.connector.Connector;
import org.apache.catalina.startup.Tomcat;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
public class DemoApplication {
public static void main(String[] args) throws LifecycleException {
class MyServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter writer = response.getWriter();
writer.println("<html>");
writer.println("<title>Welcome</title>");
writer.println("<body>Hi!</body>");
writer.println("</html>");
writer.flush();
}
}
Tomcat tomcat = new Tomcat();
Connector connector = tomcat.getConnector();
Context context = tomcat.addContext("", getAbsolutePath("."));
connector.setPort(8080);
tomcat.addServlet("", "MyServlet", new MyServlet());
context.addServletMappingDecoded("/path/to/my-servlet", "MyServlet");
tomcat.start();
Service service = tomcat.getService();
Server server = tomcat.getServer();
service.addConnector(connector);
server.await();
}
private static String getAbsolutePath(String path) {
File file = new File(path);
return file.getAbsolutePath();
}
}
Warning: it is important to keep operations order in presented source code when Tomcat Server is run - in other case it won't work.
pom.xml file:
<?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>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<name>demo</name>
<description>Demo project for Servlet</description>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<java.version>17</java.version>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
</properties>
<dependencies>
<!-- #################### -->
<!-- TOMCAT -->
<!-- #################### -->
<!-- https://mvnrepository.com/artifact/jakarta.servlet/jakarta.servlet-api -->
<dependency>
<groupId>jakarta.servlet</groupId>
<artifactId>jakarta.servlet-api</artifactId>
<version>6.0.0</version>
<scope>provided</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat.embed/tomcat-embed-core -->
<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-core</artifactId>
<version>10.1.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat.embed/tomcat-embed-jasper -->
<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-jasper</artifactId>
<version>10.1.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jasper -->
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-jasper</artifactId>
<version>10.1.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jasper-el -->
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-jasper-el</artifactId>
<version>10.1.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jsp-api -->
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-jsp-api</artifactId>
<version>10.1.13</version>
</dependency>
<!-- #################### -->
<!-- TESTING -->
<!-- #################### -->
<!-- https://mvnrepository.com/artifact/junit/junit -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.assertj/assertj-core -->
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>3.6.2</version>
<scope>test</scope>
</dependency>
<!-- #################### -->
<!-- PREPROCESSORS -->
<!-- #################### -->
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.30</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<finalName>${project.artifactId}</finalName>
<sourceDirectory>src</sourceDirectory>
<testSourceDirectory>test</testSourceDirectory>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<annotationProcessorPaths>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.30</version>
</path>
</annotationProcessorPaths>
<source>${maven.compiler.source}</source>
<target>${maven.compiler.target}</target>
<verbose>true</verbose>
</configuration>
</plugin>
</plugins>
</build>
</project>