org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'restHighLevelClient' defined in class path resource [com/esdemo/config/ElasticSearchClientConfig.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.elasticsearch.client.RestHighLevelClient]: Factory method 'restHighLevelClient' threw exception; nested exception is java.lang.NoClassDefFoundError: org/elasticsearch/common/xcontent/DeprecationHandler
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:590)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1247)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1096)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:535)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:759)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:398)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:330)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1258)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246)
	at com.esdemo.EsdemoApplication.main(EsdemoApplication.java:13)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.elasticsearch.client.RestHighLevelClient]: Factory method 'restHighLevelClient' threw exception; nested exception is java.lang.NoClassDefFoundError: org/elasticsearch/common/xcontent/DeprecationHandler
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:582)
	... 18 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/elasticsearch/common/xcontent/DeprecationHandler
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at org.elasticsearch.client.RestHighLevelClient.<clinit>(RestHighLevelClient.java:1741)
	at com.esdemo.config.ElasticSearchClientConfig.restHighLevelClient(ElasticSearchClientConfig.java:19)
	at com.esdemo.config.ElasticSearchClientConfig$$EnhancerBySpringCGLIB$$cca08d.CGLIB$restHighLevelClient$0(<generated>)
	at com.esdemo.config.ElasticSearchClientConfig$$EnhancerBySpringCGLIB$$cca08d$$FastClassBySpringCGLIB$$14e70886.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228)
	at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:361)
	at com.esdemo.config.ElasticSearchClientConfig$$EnhancerBySpringCGLIB$$cca08d.restHighLevelClient(<generated>)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	... 19 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.elasticsearch.common.xcontent.DeprecationHandler
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 43 common frames omitted

Process finished with exit code 1

Solution:

Check whether the jar package of ES is introduced into Maven’s POM file

<dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>7.7.0</version>
        </dependency>

If there is still an error after introducing the jar package, add the following to the startup class

 System.setProperty("es.set.netty.runtime.available.processors", "false");