Java Spring启动库中的可选依赖项类

我正在创建一个供内部使用的库，我想添加

springcloudstartersleuth

作为可选依赖项，因此在库的pom文件中定义了以下内容

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
    <version>1.3.0.RELEASE</version>
    <optional>true</optional>
</dependency>

在出版商

public class Publisher {
    private Tracer tracer;

    public Publisher(Tracer tracer) {
        this.tracer = tracer;
    }

    ...
    public void publish() {
         if (tracer != null) ...
    }
}

现在，当我试图将它导入到我的一个项目中时，它没有让sleuth得到以下错误

java.lang.NoClassDefFoundError: org/springframework/cloud/sleuth/Tracer
    at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_172]
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) ~[na:1.8.0_172]
    at java.lang.Class.getDeclaredMethods(Class.java:1975) ~[na:1.8.0_172]
    at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:613) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:524) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:510) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.util.ReflectionUtils.getUniqueDeclaredMethods(ReflectionUtils.java:570) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:697) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:640) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:609) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1490) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:425) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:395) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:96) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:687) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:525) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at com.demo.eventtest.EventApplication.main(EventApplication.java:16) [classes/:na]
Caused by: java.lang.ClassNotFoundException: org.springframework.cloud.sleuth.Tracer
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_172]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_172]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[na:1.8.0_172]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_172]
    ... 23 common frames omitted

更新：我尝试从自动配置和使用它的类中删除Tracer的用法，但它没有给出这个错误，所以这是唯一使用它的地方

---

它仍然试图加载

跟踪器的原因是什么？
它失败了，因为当bean类/类型在运行时不可用时，它无法在ApplicationContext中搜索bean。在尝试注入类之前，您需要检查类是否在类路径中。您可能创建了一个跟踪程序包装器，并使用
ConditionalOnClass
帮助放置该类。如果失败，则是因为
EventPublishingAutoConfiguration
导入了该类，因此类路径上需要该类。无论是否用
@Autowired
标记为可选，该类仍在加载中。而是在配置上创建条件规则，并使用字符串引用代替类。最后，将实际配置设置为静态内部类，以防止加载它。（看一看spring boot配置课程，从中获得灵感）。谢谢@M.Deinum是的，这很有帮助。
java.lang.NoClassDefFoundError: org/springframework/cloud/sleuth/Tracer
    at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_172]
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) ~[na:1.8.0_172]
    at java.lang.Class.getDeclaredMethods(Class.java:1975) ~[na:1.8.0_172]
    at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:613) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:524) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:510) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.util.ReflectionUtils.getUniqueDeclaredMethods(ReflectionUtils.java:570) ~[spring-core-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:697) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:640) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:609) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1490) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:425) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:395) ~[spring-beans-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:96) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:687) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:525) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.15.RELEASE.jar:1.5.15.RELEASE]
    at com.demo.eventtest.EventApplication.main(EventApplication.java:16) [classes/:na]
Caused by: java.lang.ClassNotFoundException: org.springframework.cloud.sleuth.Tracer
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_172]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_172]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[na:1.8.0_172]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_172]
    ... 23 common frames omitted