One of the key features of the Spring Boot framework is the built-in support for embedded servers. It includes support for embedded Tomcat, Jetty, and Undertow servers. This means you don’t need any external web servers and no need to deploy WAR files anymore. The embedded Tomcat server is available through the dependency. spring-boot-starter-web However, if you want Jetty or Undertow servers then you can include or dependencies. spring-boot-starter-jetty spring-boot-starter-undertow This article explains how to replace the default embedded Tomcat with Jetty or Undertow servers. https://youtu.be/1gEoiMVULt4?si=RVOx-P3o65KPN2-p&embedable=true Replace Tomcat With the Jetty in Spring Boot To use the embedded Jetty server instead of Tomcat, you need to exclude the from and include the dependency. Also, you will need to exclude the default added spring-boot-starter-tomcat dependency. spring-boot-starter-tomcat spring-boot-starter-web spring-boot-starter-jetty For Spring Boot Version 2.x.x For , make the following changes to your file. Gradle build.gradle dependencies {
    implementation('org.springframework.boot:spring-boot-starter-web') {
        exclude group:'org.springframework.boot', module:'spring-boot-starter-tomcat'
    }
    implementation 'org.springframework.boot:spring-boot-starter-jetty'
} If you’re using build tools, you need to add this to your file. Maven pom.xml <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId>
</dependency> For Spring Boot Version 3.x.x The above configuration works for Spring Boot version 2.x, but it will throw the following error if you’re using the latest Spring Boot version 3.x. java.lang.ClassNotFoundException: jakarta.servlet.http.HttpSessionContext 
with Spring Boot 3 and Jetty server This is because Jetty does not yet support Servlet 6.0. To use Jetty with Spring Boot 3.0, you will have to downgrade the Servlet API to 5.0. You can use the property to do so. jakarta-servlet.version Ref: Spring-Boot-3.0-Migration-Guide ext['jakarta-servlet.version'] = '5.0.0'
dependencies {
    implementation('org.springframework.boot:spring-boot-starter-web')
    implementation 'org.springframework.boot:spring-boot-starter-jetty'
    modules {
        module("org.springframework.boot:spring-boot-starter-tomcat") {
            replacedBy("org.springframework.boot:spring-boot-starter-jetty")
        }
    }
} If you’re using build tools, you need to add this to your file. Maven pom.xml <properties>
    <java.version>17</java.version>
    <jakarta-servlet.version>5.0.0</jakarta-servlet.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <exclusions>
            <exclusion>
                <artifactId>spring-boot-starter-tomcat</artifactId>
                <groupId>org.springframework.boot</groupId>
            </exclusion>
        </exclusions>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jetty</artifactId>
    </dependency>
</dependencies> Replace Tomcat With Undertow in Spring Boot To use Undertow instead of Tomcat, first, you need to exclude the spring-boot-starter-tomcat from spring-boot-starter-web. Then you should add the undertow starter as shown here. For , make the following changes to your file. Gradle build.gradle dependencies {
    implementation('org.springframework.boot:spring-boot-starter-web') {
        exclude group:'org.springframework.boot', module:'spring-boot-starter-tomcat'
    }
    implementation 'org.springframework.boot:spring-boot-starter-undertow'
} If you’re using build tools, you need to add this to your file. Maven pom.xml <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-undertow</artifactId>
</dependency> Also published here

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