Java 元信息服务
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Java Meta-Inf Services
提问by dialloc
What is the purpose of Meta-INF services in Java ?
Java 中的 Meta-INF 服务的目的是什么？
回答by kschneid
Take a look at the ServiceLoaderdocs.
回答by Marco Sigismondi
It's intended to store service provider configuration files.
它旨在存储服务提供者配置文件。
A Service provider is an implementation of a Service Provider Interface packaged as JAR.
服务提供者是打包为 JAR 的服务提供者接口的实现。
A Service loader discover and load all implementations declared in the service provider configuration file.
服务加载器发现并加载在服务提供者配置文件中声明的所有实现。
A configuration file is a file named as the fully qualified name of the interface and its content is a list of fully qualified names of implementations.
配置文件是一个以接口的完全限定名称命名的文件，其内容是实现的完全限定名称列表。
Following is an example of provider configuration file for javax.servlet.ServletContainerInitializer that is used by Servlet 3.0 at webapp startup.
以下是 Servlet 3.0 在 webapp 启动时使用的 javax.servlet.ServletContainerInitializer 的提供程序配置文件示例。
org.apache.jasper.servlet.JasperInitializer
org.springframework.web.SpringServletContainerInitializer
In this example
在这个例子中
- Tomcat is the Service Loader;
- javax.servlet.ServletContainerInitializer is the Service Provider Interface
- file named javax.servlet.ServletContainerInitializer is the Service Provider configuration file;
- org.apache.jasper.servlet.JasperInitializer and org.springframework.web.SpringServletContainerInitializer are Service providers
- Tomcat 是服务加载器；
- javax.servlet.ServletContainerInitializer 是服务提供者接口
- 名为javax.servlet.ServletContainerInitializer的文件是Service Provider的配置文件；
- org.apache.jasper.servlet.JasperInitializer 和 org.springframework.web.SpringServletContainerInitializer 是服务提供者
When tomcat startup webapp call both
当tomcat启动webapp时同时调用
onStartup(java.util.Set<java.lang.Class<?>> types, ServletContext context)
metods on JasperInitializer and SpringServletContainerInitializer classes
JasperInitializer 和 SpringServletContainerInitializer 类的方法
