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Unable to start the web server while setting-up Eureka Service, error: application missing the necessary class definition for the RestClient$Builder

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I am trying to setup a basic Eureka Service Discovery but, while implementing the same I am getting the following error:

org.springframework.context.ApplicationContextException: Unable to start web server
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:164) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:602) ~[spring-context-6.0.11.jar:6.0.11]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:146) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:436) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-3.1.2.jar:3.1.2]
    at com.project.discoveryserver.DiscoveryServerApplication.main(DiscoveryServerApplication.java:11) ~[classes/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryConfiguration$EmbeddedTomcat': org/springframework/web/client/RestClient$Builder
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:605) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:520) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:326) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:417) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1332) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1162) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:560) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:520) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:326) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:205) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.getWebServerFactory(ServletWebServerApplicationContext.java:218) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:181) ~[spring-boot-3.1.2.jar:3.1.2]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:161) ~[spring-boot-3.1.2.jar:3.1.2]
    ... 8 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/springframework/web/client/RestClient$Builder
    at org.springframework.cloud.client.loadbalancer.LoadBalancerRestClientBuilderBeanPostProcessor.postProcessBeforeInitialization(LoadBalancerRestClientBuilderBeanPostProcessor.java:46) ~[spring-cloud-commons-4.1.0.jar:4.1.0]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:419) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1762) ~[spring-beans-6.0.11.jar:6.0.11]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:598) ~[spring-beans-6.0.11.jar:6.0.11]
    ... 25 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.springframework.web.client.RestClient$Builder
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[na:na]
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[na:na]
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[na:na]
    ... 29 common frames omitted

Moreover, while mentioning the port number and other config required for the eureka server in the application.properties file, it is showing the warning that the mentioned properties are not being used. Also attaching the pom.xml, application.properties and Main class for reference:

pom.xml:

<?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">
    <parent>
        <artifactId>microservices-project</artifactId>
        <groupId>com.project</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>discovery-server</artifactId>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring-cloud.version>2023.0.0</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            <version>4.0.0</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>


    </dependencies>

</project>

application.properties:

spring.application.name=discovery-server
eureka.instance.hostname=localhost
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
server.port=8761

DiscoveryServerApplication class:

package com.project.discoveryserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@EnableEurekaServer
@SpringBootApplication
public class  DiscoveryServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(DiscoveryServerApplication.class, args);
    }
}

to resolve the same I have tried to ensure the presence of the required JAR by:

  • Checking iy my build configuration includes the spring-boot-starter-webflux dependency.
  • Verified that the JARs for WebClient are properly downloaded and included in your project's classpath.

Attaching the dependency tree for spring-boot-starter-webflux for your reference:

\- org.springframework.boot:spring-boot-starter-webflux:jar:3.1.2:compile
[INFO]    +- org.springframework.boot:spring-boot-starter:jar:3.1.2:compile
[INFO]    |  +- org.springframework.boot:spring-boot:jar:3.1.2:compile
[INFO]    |  +- org.springframework.boot:spring-boot-autoconfigure:jar:3.1.2:compile
[INFO]    |  +- org.springframework.boot:spring-boot-starter-logging:jar:3.1.2:compile
[INFO]    |  |  +- ch.qos.logback:logback-classic:jar:1.4.8:compile
[INFO]    |  |  |  \- ch.qos.logback:logback-core:jar:1.4.8:compile
[INFO]    |  |  +- org.apache.logging.log4j:log4j-to-slf4j:jar:2.20.0:compile
[INFO]    |  |  |  \- org.apache.logging.log4j:log4j-api:jar:2.20.0:compile
[INFO]    |  |  \- org.slf4j:jul-to-slf4j:jar:2.0.7:compile
[INFO]    |  +- jakarta.annotation:jakarta.annotation-api:jar:2.1.1:compile
[INFO]    |  +- org.springframework:spring-core:jar:6.0.11:compile
[INFO]    |  |  \- org.springframework:spring-jcl:jar:6.0.11:compile
[INFO]    |  \- org.yaml:snakeyaml:jar:1.33:compile
[INFO]    +- org.springframework.boot:spring-boot-starter-json:jar:3.1.2:compile
[INFO]    |  +- com.fasterxml.jackson.core:jackson-databind:jar:2.15.2:compile
[INFO]    |  +- com.fasterxml.jackson.datatype:jackson-datatype-jdk8:jar:2.15.2:compile
[INFO]    |  +- com.fasterxml.jackson.datatype:jackson-datatype-jsr310:jar:2.15.2:compile
[INFO]    |  \- com.fasterxml.jackson.module:jackson-module-parameter-names:jar:2.15.2:compile
[INFO]    +- org.springframework.boot:spring-boot-starter-reactor-netty:jar:3.1.2:compile
[INFO]    |  \- io.projectreactor.netty:reactor-netty-http:jar:1.1.9:compile
[INFO]    |     +- io.netty:netty-codec-http:jar:4.1.94.Final:compile
[INFO]    |     |  +- io.netty:netty-common:jar:4.1.94.Final:compile
[INFO]    |     |  +- io.netty:netty-buffer:jar:4.1.94.Final:compile
[INFO]    |     |  +- io.netty:netty-transport:jar:4.1.94.Final:compile
[INFO]    |     |  +- io.netty:netty-codec:jar:4.1.94.Final:compile
[INFO]    |     |  \- io.netty:netty-handler:jar:4.1.94.Final:compile
[INFO]    |     +- io.netty:netty-codec-http2:jar:4.1.94.Final:compile
[INFO]    |     +- io.netty:netty-resolver-dns:jar:4.1.94.Final:compile
[INFO]    |     |  +- io.netty:netty-resolver:jar:4.1.94.Final:compile
[INFO]    |     |  \- io.netty:netty-codec-dns:jar:4.1.94.Final:compile
[INFO]    |     +- io.netty:netty-resolver-dns-native-macos:jar:osx-x86_64:4.1.94.Final:compile
[INFO]    |     |  \- io.netty:netty-resolver-dns-classes-macos:jar:4.1.94.Final:compile
[INFO]    |     +- io.netty:netty-transport-native-epoll:jar:linux-x86_64:4.1.94.Final:compile
[INFO]    |     |  +- io.netty:netty-transport-native-unix-common:jar:4.1.94.Final:compile
[INFO]    |     |  \- io.netty:netty-transport-classes-epoll:jar:4.1.94.Final:compile
[INFO]    |     \- io.projectreactor.netty:reactor-netty-core:jar:1.1.9:compile
[INFO]    |        \- io.netty:netty-handler-proxy:jar:4.1.94.Final:compile
[INFO]    |           \- io.netty:netty-codec-socks:jar:4.1.94.Final:compile
[INFO]    +- org.springframework:spring-web:jar:6.0.11:compile
[INFO]    |  +- org.springframework:spring-beans:jar:6.0.11:compile
[INFO]    |  \- io.micrometer:micrometer-observation:jar:1.11.2:compile
[INFO]    |     \- io.micrometer:micrometer-commons:jar:1.11.2:compile
[INFO]    \- org.springframework:spring-webflux:jar:6.0.11:compile
spring-boot dependency-injection netflix-eureka service-discovery spring-boot-starter
Original Q&A
2

There are 2 answers

0
Nakshatra Singh On BEST ANSWER

The issue was resolved after changing the Spring Boot version in my parent microservice's pom.xml, attaching the pom.xml for your reference:

<?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>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.0</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.project</groupId>
    <artifactId>microservices-project</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>product_service</module>
        <module>order_service</module>
        <module>inventory_service</module>
        <module>discovery-server</module>
    </modules>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring-cloud.version>2023.0.0</spring-cloud.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.testcontainers</groupId>
                <artifactId>testcontainers-bom</artifactId>
                <version>1.19.2</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <image>
                        <builder>paketobuildpacks/builder-jammy-base:latest</builder>
                    </image>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>
0
Hrishiraj On

The Spring Cloud version for Spring Boot 3.1.5 is 2021.0.5 In your pom Add :

 <spring-cloud.version>2021.0.5</spring-cloud.version>
    <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>3.1.5</version>
            <relativePath /> 
    </parent>

or search for Spring Boot version match with Spring cloud version on Internet ,this will solve the problem.

<?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>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.5</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.project</groupId>
    <artifactId>microservices-project</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>product_service</module>
        <module>order_service</module>
        <module>inventory_service</module>
        <module>discovery-server</module>
    </modules>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring-cloud.version>2021.0.5</spring-cloud.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.testcontainers</groupId>
                <artifactId>testcontainers-bom</artifactId>
                <version>1.19.2</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <image>
                        <builder>paketobuildpacks/builder-jammy-base:latest</builder>
                    </image>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

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