spring boot 整合 es 报错：java.lang.ClassNotFoundException: org.elasticsearch.client.core.MainResponse

概述

最近由于一些原因需要升级 spring boot 版本，项目原来的版本是 spring boot 2.1.2.RELEASE，现在把版本升级到 spring boot 2.4.1，项目一启动就报如下错误，通过查阅官方文档，一步一步解决了这个问题，在这里记录一下，希望对遇到同样问题的小伙伴提供一些帮助。

说明：我使用的 elasticsearch 的版本是 6.7.0

升级spring boot 版本后报错如下

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'elasticsearchTemplate' defined in class path resource [org/springframework/boot/autoconfigure/data/elasticsearch/ElasticsearchDataConfiguration$RestClientConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate]: Factory method 'elasticsearchTemplate' threw exception; nested exception is java.lang.BootstrapMethodError: java.lang.NoClassDefFoundError: org/elasticsearch/client/core/MainResponse
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:658) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:638) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1336) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1179) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:571) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:531) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:923) ~[spring-context-5.3.2.jar:5.3.2]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:588) ~[spring-context-5.3.2.jar:5.3.2]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144) ~[spring-boot-2.4.1.jar:2.4.1]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767) [spring-boot-2.4.1.jar:2.4.1]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) [spring-boot-2.4.1.jar:2.4.1]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) [spring-boot-2.4.1.jar:2.4.1]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) [spring-boot-2.4.1.jar:2.4.1]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) [spring-boot-2.4.1.jar:2.4.1]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) [spring-boot-2.4.1.jar:2.4.1]
    at com.southcn.nfplus.NfplusEsSearchApplication.main(NfplusEsSearchApplication.java:10) [classes/:na]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate]: Factory method 'elasticsearchTemplate' threw exception; nested exception is java.lang.BootstrapMethodError: java.lang.NoClassDefFoundError: org/elasticsearch/client/core/MainResponse
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.3.2.jar:5.3.2]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:653) ~[spring-beans-5.3.2.jar:5.3.2]
    ... 20 common frames omitted
Caused by: java.lang.BootstrapMethodError: java.lang.NoClassDefFoundError: org/elasticsearch/client/core/MainResponse
    at org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate.getClusterVersion(ElasticsearchRestTemplate.java:373) ~[spring-data-elasticsearch-4.1.2.jar:4.1.2]
    at org.springframework.data.elasticsearch.core.AbstractElasticsearchTemplate.initialize(AbstractElasticsearchTemplate.java:95) ~[spring-data-elasticsearch-4.1.2.jar:4.1.2]
    at org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate.(ElasticsearchRestTemplate.java:116) ~[spring-data-elasticsearch-4.1.2.jar:4.1.2]
    at org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataConfiguration$RestClientConfiguration.elasticsearchTemplate(ElasticsearchDataConfiguration.java:74) ~[spring-boot-autoconfigure-2.4.1.jar:2.4.1]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_131]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_131]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_131]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_131]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.3.2.jar:5.3.2]
    ... 21 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/elasticsearch/client/core/MainResponse
    ... 30 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.elasticsearch.client.core.MainResponse
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_131]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_131]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) ~[na:1.8.0_131]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_131]
    ... 30 common frames omitted

原因分析

查看spring data elasticsearch 官网：Spring Data Elasticsearch 4.2.0 官方文档

有如下版本说明：

image.png

我们还可以查看 spring-boot-dependencies: 2.4.1 和 spring-boot-dependencies: 2.1.2.RELEASE 的 pom.xml 文件，搜索 elasticersearch 的版本，可以看到如下图所示的默认版本号：

image.png

image.png

从上面的分析我们可以知道，默认情况下：
spring boot 2.1.2.RELEASE 对应的 elasticsearch 版本是 6.4.3， 对应的 spring data elsaticsearch 3.1.x；
spring boot 2.4.1 对应的 elasticsearch 版本是 7.9.3， 对应的 spring data elsaticsearch 4.1.x；
所以我们可以知道，由于版本不兼容导致上面的报错，一个主要的原因是 elasticsearch 6.x 和 elasticsearch 7.x 存在版本不兼容的问题。

解决方法

从上面的分析我们已经知道是版本不兼容导致的问题，所以我们只需要手动修改为我们需要的版本即可解决此问题。
因为我这里使用的 elasticsearch 的版本是 6.7.0 ， 所以需要指定 spring data elasticsearch 的版本兼容对应的 elasticsearch 版本即可。

项目中原来的依赖如下（只列出es相关依赖），没有指定版本号，使用的是默认的版本号：

        
            org.springframework.data
            spring-data-elasticsearch
        
        
            org.elasticsearch.client
            elasticsearch-rest-high-level-client
        

修改为如下的配置，即手动指定需要的版本号：

 
        3.2.1.RELEASE
        6.7.0


        
            org.springframework.data
            spring-data-elasticsearch
            ${spring.data.elasticsearch.version}
        
        
            org.elasticsearch.client
            elasticsearch-rest-high-level-client
            ${elasticsearch.version}
        

通过上面的配置之后，再次启动项目，项目可以正常启动了。