Apache Tomcat组件层次结构处理每个不同的访问请求

Question

我正在学习Apache Tomcat并阅读关于Tomcat 6的书。第一章是关于Tomcat 6中包含的基本组件。层次结构图描述了相应的基本组件：服务器、服务、引擎、主机、上下文和Apache web服务器请求通过引擎连接、IIS通过主机、web浏览器通过上下文。我这样解释是因为每个阀门都在这个问题前面提到的每个组件级别的盒子中。

似乎几乎没有关于这个图表的文件或书籍。当apache web服务器、IIS和web浏览器请求连接到Tomcat时，是否由上述不同的组件处理？

Answer 1

绝对不是。

Tomcat收到的每个请求基本上都是：

1. 由Coyote连接器（多线程）处理。细节取决于连接器
2. 连接器最终在选择为请求提供服务的线程上调用CoyoteAdapter service
3. 请求通过引擎、主机、上下文和包装器（代表单个servlet）组件中的一系列阀门
4. 在每个servlet容器中都会调用FilterChain#doFilter方法

您可以通过在servlet中抛出异常并剖析调用堆栈来进一步了解该过程：

SEVERE: Servlet.service() for servlet [pl.copernik.servlet.HelloServlet] in context with path [/servlet-test] threw exception [null] with root cause
jakarta.servlet.ServletException
    at pl.copernik.servlet.HelloServlet.doGet(HelloServlet.java:25)
    *** Servlet API: ***
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:665)
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:774)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:223)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:158)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:185)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:158)
    *** Catalina Valves: ***
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:119)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
    *** Coyote connector details: ***
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:870)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1699)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    *** Thread pool details: ***
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:829)