指定 ServletContext setInitParameter 时，Jetty 9.4.3 不启动

【问题标题】：Jetty 9.4.3 does not start when specifying a ServletContext setInitParameter指定 ServletContext setInitParameter 时，Jetty 9.4.3 不启动
【发布时间】：2018-07-03 12:23:36
【问题描述】：

我有两个在码头上运行的同一个应用程序实例。我希望他们使用不同的数据库，所以我想指定向他们传递 conf 文件的访问配置。这是我的部署 xml 文件之一：

<Configure class="org.eclipse.jetty.webapp.WebAppContext">
  <Set name="contextPath">/app1Context</Set>
  <Set name="war">/path/to/app.war</Set>
  <!--<Get name="ServletContext">
     <Call name="setInitParameter">
       <Arg>db.config.file</Arg>
       <Arg>/path/to/databasefile1.properties</Arg>
    </Call>
  </Get>-->
</Configure>

在这种情况下，应用程序工作正常，都在每个指定的上下文中运行，但如果我取消注释：

  <!--<Get name="ServletContext">
 <Call name="setInitParameter">
   <Arg>db.config.file</Arg>
   <Arg>/path/to/databasefile1.properties</Arg>
</Call>
</Get>-->

Jetty 启动时抛出异常：

2018-01-24 12:05:22.947:WARN:oejx.XmlConfiguration:main: Config error at <Call name="setInitParameter"><Arg>db.config.file</Arg><Arg>/path/to/databasefile1.properties</Arg></Call> java.lang.reflect.InvocationTargetException in file:/path/to/descriptor.xml
2018-01-24 12:05:22.947:WARN:oejx.XmlConfiguration:main: Config error at <Get name="ServletContext"><Call name="setInitParameter"><Arg>db.config.file</Arg><Arg>/path/to/databasefile1.properties</Arg></Call></Get> java.lang.reflect.InvocationTargetException in file:/path/to/descriptor.xml
2018-01-24 12:05:22.947:WARN:oejd.DeploymentManager:main: Unable to reach node goal: started
java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.eclipse.jetty.util.TypeUtil.call(TypeUtil.java:529)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.call(XmlConfiguration.java:728)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:417)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.get(XmlConfiguration.java:675)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:420)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:358)
        at org.eclipse.jetty.xml.XmlConfiguration.configure(XmlConfiguration.java:259)
        at org.eclipse.jetty.deploy.providers.WebAppProvider.createContextHandler(WebAppProvider.java:305)
        at org.eclipse.jetty.deploy.App.getContextHandler(App.java:105)
        at org.eclipse.jetty.deploy.bindings.StandardDeployer.processBinding(StandardDeployer.java:36)
        at org.eclipse.jetty.deploy.AppLifeCycle.runBindings(AppLifeCycle.java:188)
        at org.eclipse.jetty.deploy.DeploymentManager.requestAppGoal(DeploymentManager.java:499)
        at org.eclipse.jetty.deploy.DeploymentManager.addApp(DeploymentManager.java:147)
        at org.eclipse.jetty.deploy.providers.ScanningAppProvider.fileAdded(ScanningAppProvider.java:180)
        at org.eclipse.jetty.deploy.providers.WebAppProvider.fileAdded(WebAppProvider.java:458)
        at org.eclipse.jetty.deploy.providers.ScanningAppProvider$1.fileAdded(ScanningAppProvider.java:64)
        at org.eclipse.jetty.util.Scanner.reportAddition(Scanner.java:610)
        at org.eclipse.jetty.util.Scanner.reportDifferences(Scanner.java:529)
        at org.eclipse.jetty.util.Scanner.scan(Scanner.java:392)
        at org.eclipse.jetty.util.Scanner.doStart(Scanner.java:313)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.deploy.providers.ScanningAppProvider.doStart(ScanningAppProvider.java:150)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.deploy.DeploymentManager.startAppProvider(DeploymentManager.java:561)
        at org.eclipse.jetty.deploy.DeploymentManager.doStart(DeploymentManager.java:236)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:131)
        at org.eclipse.jetty.server.Server.start(Server.java:452)
        at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:113)
        at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:113)
        at org.eclipse.jetty.server.Server.doStart(Server.java:419)

at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1511)
        at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1438)
        at java.security.AccessController.doPrivileged(Native Method)
        at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:1437)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.eclipse.jetty.start.Main.invokeMain(Main.java:222)
        at org.eclipse.jetty.start.Main.start(Main.java:486)
        at org.eclipse.jetty.start.Main.main(Main.java:79)
Caused by:
java.lang.IllegalStateException
        at org.eclipse.jetty.servlet.ServletContextHandler$Context.setInitParameter(ServletContextHandler.java:1296)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.eclipse.jetty.util.TypeUtil.call(TypeUtil.java:529)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.call(XmlConfiguration.java:728)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:417)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.get(XmlConfiguration.java:675)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:420)
        at org.eclipse.jetty.xml.XmlConfiguration$JettyXmlConfiguration.configure(XmlConfiguration.java:358)
        at org.eclipse.jetty.xml.XmlConfiguration.configure(XmlConfiguration.java:259)
        at org.eclipse.jetty.deploy.providers.WebAppProvider.createContextHandler(WebAppProvider.java:305)
        at org.eclipse.jetty.deploy.App.getContextHandler(App.java:105)
        at org.eclipse.jetty.deploy.bindings.StandardDeployer.processBinding(StandardDeployer.java:36)
        at org.eclipse.jetty.deploy.AppLifeCycle.runBindings(AppLifeCycle.java:188)
        at org.eclipse.jetty.deploy.DeploymentManager.requestAppGoal(DeploymentManager.java:499)
        at org.eclipse.jetty.deploy.DeploymentManager.addApp(DeploymentManager.java:147)
        at org.eclipse.jetty.deploy.providers.ScanningAppProvider.fileAdded(ScanningAppProvider.java:180)
        at org.eclipse.jetty.deploy.providers.WebAppProvider.fileAdded(WebAppProvider.java:458)
        at org.eclipse.jetty.deploy.providers.ScanningAppProvider$1.fileAdded(ScanningAppProvider.java:64)
        at org.eclipse.jetty.util.Scanner.reportAddition(Scanner.java:610)
        at org.eclipse.jetty.util.Scanner.reportDifferences(Scanner.java:529)
        at org.eclipse.jetty.util.Scanner.scan(Scanner.java:392)
        at org.eclipse.jetty.util.Scanner.doStart(Scanner.java:313)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)at org.eclipse.jetty.deploy.providers.ScanningAppProvider.doStart(ScanningAppProvider.java:150)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.deploy.DeploymentManager.startAppProvider(DeploymentManager.java:561)
        at org.eclipse.jetty.deploy.DeploymentManager.doStart(DeploymentManager.java:236)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:131)
        at org.eclipse.jetty.server.Server.start(Server.java:452)
        at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:113)
        at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:113)
        at org.eclipse.jetty.server.Server.doStart(Server.java:419)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1511)
        at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1438)
        at java.security.AccessController.doPrivileged(Native Method)
        at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:1437)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.eclipse.jetty.start.Main.invokeMain(Main.java:222)
        at org.eclipse.jetty.start.Main.start(Main.java:486)
        at org.eclipse.jetty.start.Main.main(Main.java:79)

我只是按照here 中描述的说明进行操作

对可能发生的事情有什么想法吗？

谢谢

【问题讨论】：

    标签： servlets parameters jetty


    【解决方案1】：

    几乎是对的。

    关键是您试图在 ServletContext 存在或尝试启动之前访问真正的 javax.servlet.ServletContext。

    在部署期间，当${jetty.base}/webapps/&lt;context&gt;.xml 被读取和处理时，ServletContext 还不存在（servlet 规范生命周期和所有），因此ServletContextHandler 提供/模仿 ServletContext 以允许您设置这些种类早期的初始化参数和属性，然后在实际 ServletContext 启动并通过 servlet 规范生命周期推送时提供给它。

    这是一个工作示例供您查看。

    首先，转储 ServletContext 属性和初始化参数，这样我们就可以看到我们的配置实际上在做什么。

    package org.eclipse.jetty.demo;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collections;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/context-info")
public class ContextInfoServlet extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
    {
        resp.setContentType("text/plain");

        PrintWriter out = resp.getWriter();
        ServletContext context = req.getServletContext();

        out.println("ServletContext attributes\n-----\n");
        Collections.list(context.getAttributeNames())
                .forEach((name) -> {
                    Object obj = context.getAttribute(name);
                    out.printf("%s: (%s) %s%n", name, obj.getClass().getName(), obj);
                });

        out.println();
        out.println("ServletContext init-params\n-----\n");
        Collections.list(context.getInitParameterNames())
                .forEach(name -> out.printf("%s: %s%n", name, context.getInitParameter(name)));

    }
}

    现在为只包含上述 servlet 的 web 应用提供一个工作的 ${jetty.base}/webapps/&lt;context&gt;.xml（Jetty XML Deployable）。

    <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "http://www.eclipse.org/jetty/configure_9_3.dtd">

<Configure class="org.eclipse.jetty.webapp.WebAppContext">
  <Set name="contextPath">/</Set>
  <Set name="war"><Property name="jetty.webapps"/>/root.war</Set>
  <Call name="setAttribute">
    <Arg>myVal</Arg>
    <Arg class="java.lang.Integer">4242</Arg>
  </Call>
  <Call name="setAttribute">
    <Arg>myPath</Arg>
    <Arg class="java.io.File">
      <New class="java.io.File">
        <Arg><SystemProperty name="java.io.tmpdir"/></Arg>
      </New>
    </Arg>
  </Call>
  <Call name="setInitParameter">
    <Arg>mySetting</Arg>
    <Arg>default</Arg>
  </Call>
  <Call name="setInitParameter">
    <Arg>anotherOption</Arg>
    <Arg>an option that your webapp needs</Arg>
  </Call>
</Configure>

    一旦使用以下start.ini 部署到新的${jetty.base} 中

    $  cat start.ini
--module=http
jetty.http.port=8080
--module=deploy
--module=annotations
--module=plus
--module=resources

    这会导致对 http://localhost:8080/context-info 的 HTTP 请求的以下输出（我已从 org.eclipse.jetty.* 和 javax.* 属性中删除了噪音，以免混淆）

    $ curl http://localhost:8080/context-info
ServletContext attributes
-----
myVal: (java.lang.String) 4242
myPath: (java.io.File) C:\Users\joakim\AppData\Local\Temp

ServletContext init-params
-----
anotherOption: an option that your webapp needs
mySetting: default

    【讨论】：

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