注释扫描不扫描类路径中的外部jar

Question

问题:Spring Component Annotation扫描没有拾取外部jar中注释的类,该类未包含在pom.xml中.但是我需要从外部jar中扫描具有特定注释的类.这些外部jar将放在类路径中,但在编译期间我的应用程序不会知道.

1)我们有一个maven模块(artifactId ="metric_processor"),它生成一个jar文件(metric_processor.jar)并有以下类

package com.metric;
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ProcessMetric {
    String name();
}

package com.metric;
public interface MetricProcessor {
   int computeMetric();
}

package com.metric;
@ProcessMetric(name="LATENCY")
@Component
public class LatencyMetricProcessor implements MetricProcessor {
    .....
}

2)我们有另一个maven模块("artifactId ="metric_processor_external"),它生成一个jar(metric_processor_external.jar)并包含"metric_processor"模块作为编译时范围.

package com.metric;
@ProcessMetric(name="TEST_METRIC_EXTERNAL")
@Component
public class TestMetricProcessor implements MetricProcessor {
    ....
}

3)我们有一个第三个(主要)maven模块(artifactId ="main_application"),它是一个独立的应用程序(使用spring),它在编译范围内包含模块"metric_processor".(但不包括"metric_processor_external").第三个模块的构建插件是

<build>
    <plugins>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>2.4</version>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <archive>
                    <manifest>
                        <mainClass>com.main.TriggerMetricProcessor</mainClass>
                    </manifest>
                </archive>
            </configuration>
            <executions>
                <execution>
                    <id>make-assembly</id>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

此模块的应用程序上下文xml是

    <beans>
        <context:component-scan base-package="com.metric">
            <context:include-filter type="annotation" expression="com.metric.ProcessMetric" />
        </context:component-scan>
        <bean id="triggerMetricProcessor" class="com.main.TriggerMetricProcessor" />
    </beans>

我有以下类,这是应用程序的起点

package com.main;

import ...

public class TriggerMetricProcessor {
    public static void main(String[] args) throws  Exception {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("application-context.xml");

        TriggerMetricProcessor triggerMetricProcessor = (TriggerMetricProcessor) context.getBean("triggerMetricProcessor");
        triggerMetricProcessor.initMetricProcessor(context);
    }

    private void initMetricProcessor(ApplicationContext context) {
        GenericBeanFactoryAccessor beanFactoryAccessor = new GenericBeanFactoryAccessor(context);
        final Map<String, Object> metricProcessors = beanFactoryAccessor.getBeansWithAnnotation(ProcessMetric.class);
        for (final Object metricProcessor : metricProcessors.values()) {
            final Class<? extends MetricProcessor> metricProcessorClass = (Class<? extends MetricProcessor>)metricProcessor.getClass();
            final ProcessMetric annotation = metricProcessorClass.getAnnotation(ProcessMetric.class);
            System.out.println("Found MetricProcessor class: " + metricProcessorClass + ", with name: " + annotation.name());
        }
    }
}

我们将第三个模块编译为

maven clean install assembly:single 

这会生成jar文件"main_application-with-dependencies.jar"

然后我们运行它

java -cp "metric_process_external.jar" -jar main_application-with-dependencies.jar

现在应用程序只找到"LatencyMetricProcessor"并且找不到"TestMetricProcessor".

有人可以帮忙吗？

Answer 1

使用-jar选项执行jar文件时,将忽略-cp选项.

-jar选项的Oracle Java文档说:

-罐

执行封装在JAR文件中的程序.第一个参数是JAR文件的名称而不是启动类名称.为了使此选项起作用,JAR文件的清单必须包含Main-Class:classname形式的一行.这里,classname标识具有public static void main(String [] args)方法的类,该方法充当应用程序的起点.有关使用Jar文件和Jar文件清单的信息,请参阅Jar工具参考页面和Java Tutorial的Jar跟踪.

使用此选项时,JAR文件是所有用户类的源,并忽略其他用户类路径设置.

另请查看这篇文章:stackoverflow.com/questions/5879925/in-linux-how-to-execute-java-jar-file-with-external-jar-files

因此,您需要使用Class-Path:标头在清单文件中指定metric_process_external.jar .您应该可以使用Maven程序集插件来执行此操作.

如果这不实用,则需要在没有-jar标志的情况下运行应用程序:

java -cp "metric_process_external.jar:main_application-with-dependencies.jar" com.main.TriggerMetricProcessor