如何在 Servlet 中不声明其类的对象的情况下调用 getServletContext
在 servlet 中，如何在不声明其类的对象的情况下调用 getServletContext？ getServletContext 在其声明中没有 static 。考虑一个例子 - ServletContext context=getServletContext();
In servlets, how does getServletContext get called without declaring an object of its class? getServletContext does not have static in its declaration. Consider for an example- ServletContext context=getServletContext();
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tl;dr
您编写的 Servlet 从其超类
HttpServlet继承了getServletContext方法，而后者又从其超类GenericServlet继承了该方法。您编写的 servlet 类的对象会由您的 Web 容器（例如 Apache Tomcat）自动实例化， Eclipse Jetty 等。请参阅 Servlet 生命周期。
您的 Servlet ➜
HttpServlet➜GenericServlet代码：
... 的缩写：
this是对运行该代码的任何对象的引用。在我们的例子中，该对象是您自己的 servlet。运行时的 servlet 是您在开发时编写的类的实例，由 Web 容器自动实例化。该类（您编写的类）是
HttpServlet。该超类HttpServlet从其超类GenericServlet。该 GenericServlet 类携带方法
getServletContext。子类HttpServlet继承该方法。您自己的类（作为 HttpServlet 的子类）也继承该方法。我怎么知道这一切？通过阅读 Javadoc。
请参阅 Jakarta Servlet 规范页面。
tl;dr
The Servlet you wrote inherits the
getServletContextmethod from its superclassHttpServlet, which in turn inherits the method from its superclassGenericServlet.An object of the servlet class you write is automatically instantiated by your web container such as Apache Tomcat, Eclipse Jetty, etc. See Servlet Life Cycle in the Servlet specification.
Your Servlet ➜
HttpServlet➜GenericServletThe code:
… is short for:
The
thisis a reference to whatever object is running that code. In our case here, that object is your own servlet.Your servlet at runtime is an instance of the class you wrote at development time, automatically instantiated by your web container. That class, the class you authored, is a subclass of
HttpServlet. That superclassHttpServletextends from its superclassGenericServlet.That
GenericServletclass carries the methodgetServletContext. The subclassHttpServletinherits that method. And so too does your own class, as a subclass ofHttpServlet, inherit that method.How do I know all this? By reading the Javadoc.
See the Jakarta Servlet specification page.