Jetty 9.4.3 does not start when specifying a ServletContext setInitParameter - servlets

Question

I have two instances of the same app running on jetty. I want them to use differents DB so I would like to specify the access configuration passing them a conf file. This is one of my deploy xml file:
<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>
In this case the apps are working fine, both running in each spefified context but if I uncomment this:
<!--<Get name="ServletContext">
<Call name="setInitParameter">
<Arg>db.config.file</Arg>
<Arg>/path/to/databasefile1.properties</Arg>
</Call>
</Get>-->
Jetty throws an exception at start:
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)
I am just following the instructions described here
Any ideas of what could be happening?
Thanks

Answer 1

Almost got it right.
The crux is you are attempting to access the real javax.servlet.ServletContext before the ServletContext even exists or has been attempted to be started.
During the deployment, when the ${jetty.base}/webapps/<context>.xml is read and processed, the ServletContext doesn't exist yet (the servlet spec lifecycle and all), so the ServletContextHandler provides/mimics the ServletContext to allow you to set these kinds of init-parameters and attributes early, which are then made available to the actual ServletContext later when it is being started and pushed through the servlet spec lifecycle.
Here's a working example for you to review.
First, something to dump the ServletContext attributes and init-parameters, so we can see what our configuration is actually doing.
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)));
}
}
Now for a working ${jetty.base}/webapps/<context>.xml (Jetty XML Deployable) for a webapp that contains just the above servlet.
<?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>
Once deployed into a fresh ${jetty.base} with the following start.ini
$ cat start.ini
--module=http
jetty.http.port=8080
--module=deploy
--module=annotations
--module=plus
--module=resources
This results in the following output from an HTTP request to http://localhost:8080/context-info (I've removed the noise from the org.eclipse.jetty.* and javax.* attributes to not confuse things)
$ 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