java - Servlet 多次初始化
问题描述
我们正在部署一个 IIS 站点,其中包括几个文件夹、几个虚拟目录和一个 Tomcat 主机。
在 Java 8 上运行 Tomcat 8 (8.0.46) 时,一切都很好。升级到JDK 9(OpenJDK 64-Bit Server VM(build 9.0.4+11,混合模式))后,我们注意到每个servlet都被初始化了几次(即方法init(ServletConfig)被执行了几次),第一个主机上下文上的时间(如预期),并为站点中的每个文件夹更改一次。
不希望的副作用是 servlet 创建的临时文件/日志在站点的每个文件夹中重复。
Tomcat server.xml 包含主机定义:
<Host name="localhost" appBase="C:/Program Files (x86)/b4/Controller/bin/webserver/ebsc_web"
unpackWARs="true" autoDeploy="true">
<Context path="/servlets" docBase="C:/Program Files (x86)/b4/Controller/bin/webserver\ebsc_web\" xmlValidation="false" xmlNamespaceAware="false">
<WatchedResource>WEB-INF/web.xml</WatchedResource>
</Context>
<!--
<Valve className="org.apache.catalina.authenticator.SingleSignOn" />
-->
<!-- Access log processes all example.
Documentation at: /docs/config/valve.html
Note: The pattern used is equivalent to using pattern="common" -->
<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
prefix="localhost_access_log" suffix=".txt"
pattern="%h %l %u %t "%r" %s %b" />
</Host>
相同的位置(C:\Program Files (x86)\b4\Controller\bin\webserver\ebsc_web)是网站的物理路径,包括子文件夹,例如:applet、images等。启动Tomcat时会创建日志在默认位置 (ebsc_web) 并在每个子文件夹中复制。
我们注意到,当 servlet 在正确的 servlet 上下文中初始化时,堆栈是:
Daemon Thread [localhost-startStop-1] (Suspended (breakpoint at line 49 in UpdateSchedulerLoader))
owns: StandardWrapper (id=63)
owns: StandardContext (id=64)
UpdateSchedulerLoader.init(ServletConfig) line: 49
StandardWrapper.initServlet(Servlet) line: 1227
StandardWrapper.loadServlet() line: 1140
StandardWrapper.load() line: 1027
StandardContext.loadOnStartup(Container[]) line: 5038
StandardContext.startInternal() line: 5348
StandardContext(LifecycleBase).start() line: 145
ContainerBase$StartChild.call() line: 1408
ContainerBase$StartChild.call() line: 1398
FutureTask<V>.run() line: 264
ThreadPoolExecutor.runWorker(ThreadPoolExecutor$Worker) line: 1167
ThreadPoolExecutor$Worker.run() line: 641
Thread.run() line: 844
但是,当它使用指向子文件夹的 servlet 上下文初始化时,堆栈是:
Daemon Thread [localhost-startStop-1] (Suspended (breakpoint at line 42 in UpdateSchedulerLoader))
owns: StandardWrapper (id=154)
owns: StandardContext (id=144)
UpdateSchedulerLoader.init(ServletConfig) line: 42
StandardWrapper.initServlet(Servlet) line: 1227
StandardWrapper.loadServlet() line: 1140
StandardWrapper.load() line: 1027
StandardContext.loadOnStartup(Container[]) line: 5038
StandardContext.startInternal() line: 5348
StandardContext(LifecycleBase).start() line: 145
StandardHost(ContainerBase).addChildInternal(Container) line: 753
StandardHost(ContainerBase).addChild(Container) line: 729
StandardHost.addChild(Container) line: 717
HostConfig.deployDirectory(ContextName, File) line: 1129
HostConfig$DeployDirectory.run() line: 1871
Executors$RunnableAdapter<T>.call() line: 514
FutureTask<V>.run() line: 264
ThreadPoolExecutor.runWorker(ThreadPoolExecutor$Worker) line: 1167
ThreadPoolExecutor$Worker.run() line: 641
Thread.run() line: 844
所以第一次 servlet 由 初始化ContainerBase$StartChild.call()
,之后由HostConfig.deployDirectory(ContextName, File)
...
你能解释/修复这种行为吗?
解决方案
根据@PiotrP.Karwasz 的指示,通过autoDeploy="false" deployOnStartup="false"
在 server.xml 中的主机配置中设置两者,该问题已得到解决。
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