VSCode Java extension gives error "Cannot find the class file for javax.servlet.http.HttpServletResponse."

I have a java project using gradle as my build system. I am developing in VSCode using the Java extension by Redhat. I am developing on Ubuntu 20.04 with openjdk 11.

When I build the project from the command line using './gradlew assemble', I don't get any build error.

But when I open the project in vscode, I get the following problem in the problems view...

The project was not built since its build path is incomplete. Cannot find the class file for javax.servlet.http.HttpServletResponse. Fix the build path then try building this project

and...

The type javax.servlet.http.HttpServletResponse cannot be resolved. It is indirectly referenced from required .class files

My build.gradle is as follows....

plugins {
  id 'com.google.cloud.tools.jib' version '2.4.0'
}

apply plugin: 'java'

// Use maven repository
repositories {
    mavenCentral()
    google()
    maven { url 'https://jitpack.io' }
}

dependencies {
    implementation 'org.eclipse.jetty:jetty-servlet:9.4.19.v20190610'
    implementation 'org.eclipse.jetty:jetty-client:9.4.19.v20190610'
    implementation group: 'org.eclipse.jetty', name: 'jetty-util', version: '9.4.29.v20200521'

    implementation 'mysql:mysql-connector-java:8.0.16'
    implementation 'com.google.cloud.sql:mysql-socket-factory-connector-j-8:1.0.16'
    implementation 'org.apache.commons:commons-dbcp2:2.7.0'
    implementation 'org.jdbi:jdbi3-core:3.10.1'
    implementation 'com.google.firebase:firebase-admin:6.11.0'
    implementation 'com.google.apis:google-api-services-oauth2:v1-rev155-1.25.0'

    implementation group: 'ch.qos.logback', name: 'logback-classic', version: '1.2.3'
    implementation group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.0.1'
    implementation group: 'org.reflections', name: 'reflections', version: '0.9.12'

    implementation 'com.github.bhlangonijr:chesslib:1.2.3'

    // compile project('chesslib')
    //runtime files('../../chesslib/build/libs/chesslib-1.1.12.jar')
}

task runServer(type: JavaExec) {
    enableAssertions = true
    classpath = sourceSets.main.runtimeClasspath 
    main = 'ChessServer'
} 

task runClient(type: JavaExec) {
    classpath = sourceSets.main.runtimeClasspath 
    main = 'ChessClient'
    standardInput = System.in // without this, using Scanner on System.in won't work
}

task runCLITestApp(type: JavaExec) {
    classpath = sourceSets.main.runtimeClasspath 
    main = 'CLITestApp'
    standardInput = System.in
}

// use cloudBuilder.py to invoke this jib task to build the container
// use cloudConfiguration.json to configure things like container version.
jib {
    if (project.hasProperty('googleCloudProjectName') && project.hasProperty('imageName')) {
        to {
          image = "gcr.io/$googleCloudProjectName/$imageName"
        }
        container {
            mainClass = 'ChessServer'
            ports = ['8080']
            creationTime = "USE_CURRENT_TIMESTAMP"
        }
    }
}

// make sure the required project properties are set for jib
task jibCheck {
    doLast {
        if (!project.hasProperty('googleCloudProjectName'))
            throw new GradleException("When invoking the jib task, make sure to pass the cli arg -PgoogleCloudProject=[myGoogleCloudProject]\nThis should be the name of the google cloud project which container registry you want to push to.");
        if (!project.hasProperty('imageName'))
            throw new GradleException("When invoking the jib task, make sure to pass the cli arg -PimageName=[imageName]");
    }
}
tasks.jib.dependsOn tasks.jibCheck

// src/main/jib is the default folder that jib looks for files to add to your container
// these files will be placed in the root / dir of the container
task moveFilesForJib(type: Copy) {
    from "releaseFiles"
    into "src/main/jib"
}
tasks.jib.dependsOn tasks.moveFilesForJib