从嵌入式 OSGi 框架使用 Log4j2

Question

我们使用Apache Felix (version 4.4.1)嵌入式 OSGi 框架。提供框架的主要应用程序用作Log4j2 (version 2.0.1)日志记录框架。log4j-api 和 log4j-core 存在依赖关系。当然，当主应用程序启动时，Log4j2 也会被加载和配置。在主要部分中触发的所有日志消息都会正确写入配置的附加程序。

现在是重点。加载的所有包应该能够使用相同的配置，并且使用与主应用程序相同的 LoggingContext。我试图做的是将所有 Log4j2 包（来自 log4j2-api 和 log4j-core）作为org.osgi.framework.system.packages.extra. 但是，当加载捆绑包时，log4j2 包不会像其他提供的包那样出现在接线包列表中，并且当捆绑包类尝试访问 Log4j2 类时，将引发异常。

所有捆绑包都以相同的方式配置，并且 Log4j2 依赖于 log4j2-api 和 log4j2-core 并提供了范围。当我查看 MANIFEST.MF 时，使用的 Log4j2 包位于该Import-Packages部分内

所以我的问题是。

为什么以这种方式导出 Log4j2 包不起作用？我必须如何配置我的环境，以便我可以在我的包和主应用程序中使用相同的 LoggingContext？

这是我在 java 代码中的 OSGi 框架的配置部分：

Map<String, String> temp = new HashMap<String, String>();
// setting parameter that the felix cache is new initialized on each
// start of the application
temp.put(org.osgi.framework.Constants.FRAMEWORK_STORAGE_CLEAN, "onFirstInit");
// setting the packages that are provided by the main system and can
// be used by the osgi bundles
temp.put(org.osgi.framework.Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA,
// have to export these explicitly as the automatic export does
// not work for this internal java packages
+ "com.sun.org.apache.xerces.internal.dom,"
+ "com.sun.org.apache.xerces.internal.jaxp,"
+ "com.sun.org.apache.xerces.internal.util,"
// export the looging packages
+ "org.apache.log4j," + "org.apache.logging.log4j," +   "org.apache.logging.log4j.message,"
+ "org.apache.logging.log4j.simple," + "org.apache.logging.log4j.spi,"
+ "org.apache.logging.log4j.status," + "org.apache.logging.log4j.util,"
+ "org.apache.logging.log4j.impl," + "org.apache.logging.log4j.appender,"
+ "org.apache.logging.log4j.appender.db," + "org.apache.logging.log4j.appender.db.jdbc,"
+ "org.apache.logging.log4j.appender.db.jpa," + "org.apache.logging.log4j.appender.db.jpa.converter,"
+ "org.apache.logging.log4j.appender.jms," + "org.apache.logging.log4j.appender.rewrite,"
+ "org.apache.logging.log4j.appender.rolling," + "org.apache.logging.log4j.appender.rolling.action,"
+ "org.apache.logging.log4j.appender.routing," + "org.apache.logging.log4j.async,"
+ "org.apache.logging.log4j.config," + "org.apache.logging.log4j.config.json,"
+ "org.apache.logging.log4j.config.plugins," + "org.apache.logging.log4j.config.plugins.osgi,"
+ "org.apache.logging.log4j.config.plugins.processor,"
+ "org.apache.logging.log4j.config.plugins.util," + "org.apache.logging.log4j.config.plugins.visitors,"
+ "org.apache.logging.log4j.config.status," + "org.apache.logging.log4j.config.xml,"
+ "org.apache.logging.log4j.config.yaml," + "org.apache.logging.log4j.filter,"
+ "org.apache.logging.log4j.impl," + "org.apache.logging.log4j.jackson,"
+ "org.apache.logging.log4j.jmx," + "org.apache.logging.log4j.layout,"
+ "org.apache.logging.log4j.lookup," + "org.apache.logging.log4j," + "org.apache.logging.log4j.net,"
+ "org.apache.logging.log4j.net.jms," + "org.apache.logging.log4j.net.server,"
+ "org.apache.logging.log4j.net.ssl," + "org.apache.logging.log4j.pattern,"
+ "org.apache.logging.log4j.selector," + "org.apache.logging.log4j.tools,"
+ "org.apache.logging.log4j.util," + "sun.misc," + "javax.jms," + "javax.mail,"
+ "javax.mail.internet," + "javax.mail.util," + "javax.persistence," + "javax.servlet,"
+ "com.sun.xml.internal.bind");
temp.put(FelixConstants.LOG_LEVEL_PROP, "4");
OSGI_CONFIG = Collections.unmodifiableMap(temp);

捆绑包中 log4j2 库的依赖关系定义如下：

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.0.1</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.0.1</version>
    <scope>provided</scope>
</dependency>

Answer 1

我们找到了一个适用于 2.0.1 版本的解决方案。Import-Package我们没有在 MANIFEST.MF 部分中设置所需的 log4j 包，而是将它们添加到DynamicImport-Package定义中。之后，类会在需要时动态连接，并且所有 OSGi 包都可以使用相同的 LoggerContext。