添加千分尺依赖性导致奇怪的Spring代理问题 [英] Adding micrometer dependency causes weird Spring proxy issue
问题描述
我有一个带有私有@Scheduled方法的简单Spring Boot应用程序:
I have a simple Spring Boot application with private @Scheduled method:
@SpringBootApplication
@EnableScheduling
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
@Scheduled(fixedRate = 1000)
private void scheduledTask() {
System.out.println("Scheduled task");
}
}
pom.xml:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.8.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--<dependency>
<groupId>io.micrometer</groupId>
<artifactId>micrometer-spring-legacy</artifactId>
<version>1.1.1</version>
</dependency>
<dependency>
<groupId>io.micrometer</groupId>
<artifactId>micrometer-registry-prometheus</artifactId>
<version>1.1.1</version>
</dependency>-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.8.11</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.8.11</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
当千分尺依赖性并注释掉时，一切都按预期工作，但是当我取消注释时，发生以下异常:
When micrometer dependencies and commented out everything works as expected, but when I uncomment them, following exception occurs:
Caused by: java.lang.IllegalStateException: Need to invoke method 'scheduledTask' found on proxy for target class 'DemoApplication' but cannot be delegated to target bean. Switch its visibility to package or protected.
at org.springframework.aop.support.AopUtils.selectInvocableMethod(AopUtils.java:133) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.processScheduled(ScheduledAnnotationBeanPostProcessor.java:343) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
at org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor.postProcessAfterInitialization(ScheduledAnnotationBeanPostProcessor.java:326) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:423) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1633) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
... 15 common frames omitted
有人知道下发生了什么吗?
Does anyone have an idea what's going on underneath?
我认为mictometer和AspectJ依赖项之间存在某种冲突，只有在classpath中都存在两者时，才会出现此问题.
I think there is some kind of conflict between mictometer and aspectJ dependencies, the issue occurs only if both are present on classpath.
推荐答案
Spring建议通常在可能的情况下通过JDK代理实现，JDK代理需要一个接口来动态实现(执行有趣的逻辑然后委托给您的业务代码).在这种情况下，您有一个实际的类，因此Spring最好的方法是对其进行子类化.
Spring advice is usually implemented when possible with JDK proxies, which require an interface to implement dynamically (which does the interesting logic and then delegates to your business code). In a case like this, you have an actual class, so the best Spring can do is to subclass it.
但是，这里有两个相互矛盾的要求:Spring想要应用建议来捕获代码的度量，但是由于方法是private，因此无法从子类访问它. (实际上，我对使用私有方法检测并调用您的计划任务感到非常惊讶.)
However, there are two conflicting requirements here: Spring wants to apply advice that captures metrics for your code, but since the method is private, it isn't accessible from a subclass. (I'm actually moderately surprised it's detecting and calling your scheduled task with a private method.)
将方法更改为protected允许Spring在运行时执行此操作(不是实际的Java代码，而是等效的生成字节码):
Changing your method to protected allows Spring to do this at runtime (not actual Java code, but the equivalent generated bytecode):
class DemoApplicationWithAdvice extends DemoApplication {
@Override
protected void scheduledTask() {
// record start time
super.scheduledTask();
// write metric with execution time
}
}
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