How to disable directory listing for Jetty's WebAppContext?

You can set org.eclipse.jetty.servlet.Default.dirAllowed instead of dirAllowed:

webAppContext.setInitParameter("org.eclipse.jetty.servlet.Default.dirAllowed", "false");

Tested for Jetty 7.4.5.v20110725, 8.1.4.v20120524, 9.0.2.v20130417 and 9.2.0.v20140526.

For anyone using web.xml, you can also disallow it there. Find the default servlet (the one with Jetty's DefaultServlet), and set the dirAllowed parameter to false:

<servlet>
    <servlet-name>default</servlet-name>
    <servlet-class>org.eclipse.jetty.servlet.DefaultServlet</servlet-class>
    <init-param>
        <param-name>dirAllowed</param-name>
        <param-value>false</param-value>
    </init-param>
</servlet>

This works for me on Jetty v9.4.3:

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <context-param>
        <param-name>org.eclipse.jetty.servlet.Default.dirAllowed</param-name>
        <param-value>false</param-value>
    </context-param>

</web-app>