Getting java.lang.ClassNotFoundException: jakarta.servlet.Filter on Maven/Jersey web service while running on Tomcat 9

Question

While running on Tomcat 9 server with the following resource, I am getting error java.lang.ClassNotFoundException: jakarta.servlet.Filter

The following is the pom.xml file

<modelVersion>4.0.0</modelVersion>

<groupId>com.telusko</groupId>
<artifactId>demorest</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>demorest</name>

<build>
    <finalName>demorest</finalName>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.5.1</version>
            <inherited>true</inherited>
            <configuration>
                <source>1.7</source>
                <target>1.7</target>
            </configuration>
        </plugin>
    </plugins>
</build>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.glassfish.jersey</groupId>
            <artifactId>jersey-bom</artifactId>
            <version>${jersey.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet-core</artifactId>
        <!-- use the following artifactId if you don't need servlet 2.x compatibility -->
        <!-- artifactId>jersey-container-servlet</artifactId -->
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.inject</groupId>
        <artifactId>jersey-hk2</artifactId>
    </dependency>
    
    
    <!-- https://mvnrepository.com/artifact/com.sun.jersey/jersey-core -->

    
    <!-- uncomment this to get JSON support
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-json-binding</artifactId>
    </dependency>
    
    -->
</dependencies>
<properties>
    <jersey.version>3.0.0-M6</jersey.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties> </project>

The following is the web.xml file with the demorest project.

<?xml version="1.0" encoding="UTF-8"?>
<!-- This web.xml file is not required when using Servlet 3.0 container,
     see implementation details http://jersey.java.net/nonav/documentation/latest/jax-rs.html -->
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <servlet>
        <servlet-name>Jersey Web Application</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>com.telusko.demorest</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Jersey Web Application</servlet-name>
        <url-pattern>/webapi/*</url-pattern>
    </servlet-mapping>
</web-app>

The resource file that was created is as follows:

package com.telusko.demorest;

import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.MediaType;

/**
 * Root resource (exposed at "myresource" path)
 */
@Path("myresource")
public class MyResource {

    /**
     * Method handling HTTP GET requests. The returned object will be sent
     * to the client as "text/plain" media type.
     *
     * @return String that will be returned as a text/plain response.
     */
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getIt() {
        return "Got it!";
    }
}

Answer 1

java.lang.ClassNotFoundException: jakarta.servlet.Filter

This class is part of Servlet API version 5.0 which in turn is part of Jakarta EE version 9.

And,

<jersey.version>3.0.0-M6</jersey.version>

this Jersey version is based off JAX-RS API version 3.0 which in turn is part of Jakarta EE version 9.

And,

Tomcat 9 server

this Tomcat version is based off Servlet API version 4.0 which in turn is part of Java/Jakarta EE version 8.

So, summarized, the targeted JEE versions don't match up and it's causing trouble for you. You have 2 options:

1. Downgrade Jersey to version 2.x. This one is based off JAX-RS API version 2.x which in turn is part of Java/Jakarta EE version 8.

2. Or, upgrade Tomcat to version 10.x. This one is based off Servlet API version 5.0 which in turn is part of Jakarta EE version 9 (which in turn offers JAX-RS API version 3.x for which you can thus use the intended Jersey version).

The technical reason is that during the step from Java/Jakarta EE 8 to Jakarta EE 9 all javax.* packages have been renamed to jakarta.* packages. So there is no backwards compatibility anymore since Jakarta EE 9. The target runtime itself (thus, Tomcat itself), has really to be the one targeted for the APIs in use by Jakarta EE 9.

See also:

• Apache Tomcat - Versions
• Tomcat 9 casting servlets to javax.servlet.Servlet instead of jakarta.servlet.http.HttpServlet (this answer contains complete examples of proper pom.xml declarations for Tomcat 10+, Tomcat 9-, JEE 9+ and JEE 8-).