Apache Camel 4.8.0中MicrometerObservationTracer类未找到异常求助

问题场景 #

在基于Spring Boot的Apache Camel 4.8.0项目中，尝试通过Micrometer和Brave启用链路追踪，配置了以下依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>io.zipkin.reporter2</groupId>
    <artifactId>zipkin-reporter-brave</artifactId>
</dependency>
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-tracing-bridge-brave</artifactId>
</dependency>
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-micrometer</artifactId>
    <version>4.8.0</version>
</dependency>
<dependency>
    <groupId>org.apache.camel.springboot</groupId>
    <artifactId>camel-observation-starter</artifactId>
    <version>4.8.0</version>
</dependency>

启动时抛出ClassNotFoundException，具体异常栈如下：

Caused by: java.lang.IllegalStateException: Failed to introspect Class [org.apache.camel.observation.starter.ObservationAutoConfiguration] from ClassLoader [jdk.internal.loader.ClassLoaders$AppClassLoader@76ed5528]
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:483)
at org.springframework.util.ReflectionUtils.doWithLocalMethods(ReflectionUtils.java:320)
at org.springframework.core.type.StandardAnnotationMetadata.getAnnotatedMethods(StandardAnnotationMetadata.java:149)
at org.springframework.context.annotation.ConfigurationClassParser.retrieveBeanMethodMetadata(ConfigurationClassParser.java:413)
at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:336)
at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:246)
at org.springframework.context.annotation.ConfigurationClassParser.processImports(ConfigurationClassParser.java:534)
... 17 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/apache/camel/observation/MicrometerObservationTracer
at java.base/java.lang.Class.getDeclaredMethods0(Native Method)
at java.base/java.lang.Class.privateGetDeclaredMethods(Class.java:3578)
at java.base/java.lang.Class.getDeclaredMethods(Class.java:2676)
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:465)
... 23 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.camel.observation.MicrometerObservationTracer
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
... 27 common frames omitted

解决方案 #

缺失的org.apache.camel.observation.MicrometerObservationTracer类属于**camel-micrometer-observation**模块，需要添加对应的Spring Boot Starter依赖到pom.xml中：

<dependency>
    <groupId>org.apache.camel.springboot</groupId>
    <artifactId>camel-micrometer-observation-starter</artifactId>
    <version>4.8.0</version>
</dependency>

补充说明 #

• 原有的camel-micrometer是传统的Micrometer指标收集依赖，而camel-micrometer-observation是基于Micrometer Observation API实现的链路追踪集成，与camel-observation-starter配套使用。
• 确保该依赖的版本与项目中Camel的版本（4.8.0）完全一致，避免版本不兼容问题。

内容的提问来源于stack exchange，提问作者Praveen kumar