获取OpenSearch索引时出现RestHighLevelClient引导方法初始化异常

尝试从OpenSearch获取索引时抛出以下异常：

Exception in thread "main" java.lang.BootstrapMethodError: bootstrap method initialization exception
at java.base/java.lang.invoke.BootstrapMethodInvoker.invoke(BootstrapMethodInvoker.java:194)
at java.base/java.lang.invoke.CallSite.makeSite(CallSite.java:307)
at java.base/java.lang.invoke.MethodHandleNatives.linkCallSiteImpl(MethodHandleNatives.java:258)
at java.base/java.lang.invoke.MethodHandleNatives.linkCallSite(MethodHandleNatives.java:248)
at org.opensearch.client.RestClient.convertResponse(RestClient.java:361)
at org.opensearch.client.RestClient.performRequest(RestClient.java:345)
at org.opensearch.client.RestClient.performRequest(RestClient.java:320)
at org.opensearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1918)
at org.opensearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1901)
at org.opensearch.client.RestHighLevelClient.performRequestAndParseEntity(RestHighLevelClient.java:1865)
at org.opensearch.client.IndicesClient.get(IndicesClient.java:768)
at com.QueriesTest.main(QueriesTest.java:99)
Caused by: java.lang.invoke.LambdaConversionException: Invalid receiver type interface org.apache.http.Header; not a subtype of implementation type interface org.apache.http.NameValuePair
at java.base/java.lang.invoke.AbstractValidatingLambdaMetafactory.validateMetafactoryArgs(AbstractValidatingLambdaMetafactory.java:254)
at java.base/java.lang.invoke.LambdaMetafactory.metafactory(LambdaMetafactory.java:328)
at java.base/java.lang.invoke.BootstrapMethodInvoker.invoke(BootstrapMethodInvoker.java:127)
... 11 more

版本信息：

• JDK 11
• 构建配置：plugins { id:'org.springframework.boot' version '1.5.6.RELEASE' }
• OpenSearch依赖：opensearch-java:2.6.0、opensearch-rest-high-level-client:2.9.0

相关代码：

static RestHighLevelClient client = new RestHighLevelClient(
            RestClient.builder(new HttpHost(domainUrl, port, protocol)));

//QueriesTest.java:99
GetIndexRequest request = new GetIndexRequest(indexName); 
GetIndexResponse response = client.indices().get(request, RequestOptions.DEFAULT);

这个异常的核心是Apache HttpClient版本冲突，具体细节：

1. Spring Boot 1.5.6.RELEASE默认依赖Apache HttpClient 4.x版本，而OpenSearch 2.x客户端依赖的是HttpClient 5.x版本。
2. 两个版本中org.apache.http.Header和org.apache.http.NameValuePair的继承关系发生了变化：HttpClient 4.x里Header是NameValuePair的子接口；但HttpClient 5.x中两者没有继承关系。
3. OpenSearch客户端代码用Lambda表达式尝试将Header转换为NameValuePair，版本冲突导致类型校验失败，触发LambdaConversionException，最终引发BootstrapMethodError。
4. 同时opensearch-java和opensearch-rest-high-level-client版本不匹配，进一步加剧了依赖冲突问题。

1. 统一OpenSearch客户端版本 #

确保两个OpenSearch依赖使用相同版本，比如都用2.9.0：

implementation 'org.opensearch.client:opensearch-rest-high-level-client:2.9.0'
implementation 'org.opensearch.client:opensearch-java:2.9.0'

2. 排除Spring Boot自带的HttpClient 4.x依赖 #

在构建配置中排除旧版HttpClient，强制使用OpenSearch依赖的HttpClient 5.x：

configurations.all {
    exclude group: 'org.apache.httpcomponents', module: 'httpclient'
    exclude group: 'org.apache.httpcomponents', module: 'httpcore'
}

3. 手动引入HttpClient 5.x依赖（可选） #

如果排除旧依赖后出现缺失，可手动添加HttpClient 5.x核心包：

implementation 'org.apache.httpcomponents.client5:httpclient5:5.2.1'
implementation 'org.apache.httpcomponents.core5:httpcore5:5.2.1'

4. 升级Spring Boot版本（推荐） #

Spring Boot 1.5.x已停止维护，建议升级到支持HttpClient 5.x的版本（如2.7.x或更高），从根源上避免依赖冲突。

内容的提问来源于stack exchange，提问作者Shah Shahid