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Chapter 3. Jetty Configuration Introduction

Table of Contents

How to Configure Jetty
What to Configure in Jetty

How to Configure Jetty

To understand Jetty configuration, you need to understand the "How" and the "What". This section covers how to configure Jetty in terms of what mechanisms exist to perform configuration. The next section gives an overview of the action components and fields that you can configure with these mechanisms.

Jetty POJO Configuration

The core components of Jetty are simply Plain Old Java Objects (POJOs); the process of configuring Jetty is mostly the process of instantiating, assembling and setting fields on the Jetty POJOs. You can achieve this either by:

  • Writing Java code to directly instantiate and assemble Jetty objects. This is referred to as Embedding Jetty.

  • Using Jetty XML configuration, which is an Inversion of Control (IoC) framework, to instantiate and assemble Jetty objects as XML objects. The etc/jetty.xml file is the main Jetty XML configuration file, but there are many other etc/jetty-feature.xml files included in the jetty distribution.

  • Using a third party IoC framework like Spring, to instantiate and assemble Jetty objects as Spring beans.

Because the main Jetty configuration is done by IoC, the Jetty API documentation is the ultimate configuration reference.

Jetty Start Configuration Files

The Jetty distribution uses the following configuration files to instantiate, inject and start server via the start.jar mechanism

ini files

The Jetty Start mechanism uses the command line, the $JETTY_BASE/start.ini and/or $JETTY_BASE/start.d/*.ini files to create an effective command line of arguments. Arguments may be:

  • XML files in Jetty IoC (or spring) XML format

  • Module activations in the form --module=name

  • Property in the form of name=value, used to parameterize Jetty IoC XML

  • A standard Java property file containing additional start properties

  • Other start.jar options (see java -jar start.jar --help)

  • Some JVM options

It is the ini files are located in the jetty base (if different from jetty home) that are typically edited to change the configuration (Eg change ports)

mod files

The $JETTY_HOME/modules/*.mod files contain the definition of modules that can be activated by --module=name. Each mod file defines:

  • Module dependencies for ordering and activation

  • The libraries needed by the module to be added to the classpath

  • The XML files needed by the module to be added to the effective command line

  • Files needed by the activated module

  • A template ini file to be used when activating with the --add-to-start=name option

Typically module files are rarely edited and only for significant structural changes. The *.mod files are normally located $JETTY_HOME/modules/, but extra or edited modules may be added to $JETTY_BASE/module. If module changes are required, it is best practise to copy the particular *.mod file from $JETTY_HOME/modules/ to $JETTY_BASE/modules/ before being modified.

XML files

XML files in Jetty IoC XML format or spring IoC format are listed either on the command line, in ini files or are added to the effective command line by a module definition. The XML files instantiate and inject the actual Java objects that comprise the server, connectors and contexts. Because Jetty IoC XML files use properties, most common configuration tasks can be accomplished without editing these XML files and can instead be achieved by editing the properti in the corresponding ini files.

The XML files are normally located $JETTY_HOME/etc/, but extra or edited XML files may be added to $JETTY_BASE/etc/. If XML configuration changes are required, it is best practise to copy the XML file from $JETTY_HOME/etc/ to $JETTY_BASE/etc/ before being modified.

Other Configuration Files

In addition to the start configuration files described above, the configuration of the server can use the following file:

Context XML files

Any XML files in Jetty IoC XML format or spring IoC format that is discovered in the webapps directory are used by the deploy module to instantiate and inject HttpContext instances to create a specific context. These may be standard web applications or bespoke contexts created from special purpose handlers.

web.xml

The Servlet Specification defines the web.xml deployment descriptor that defines and configures the filters, servlets and resources a web application uses. The Jetty WebAppContext component uses this XML format to:

  • Set up the default configuration of a web application context.

  • Interpret the application-specific configuration supplied with a web application in the WEB-INF/web.xml file.

  • Interpret descriptor fragments included in the META-INF directory of Jar files within WEB-INF/lib.

Normally the web.xml file for a web application is found in the WEB-INF/web.xml location within the war file/directory or as web.xml fragments with jar files found in WEB-INF/lib. Jetty also supports multiple web.xml files so that a default descriptor may be applied before WEB-INF/web.xml (typically set to etc/webdefault.xml by the deploy module) and an override descriptor may be applied after WEB-INF/web.xml (typically set by a context XML file see test.xml)

Property Files

Standard Java property files are also used for Jetty configuration in several ways:

  • To parameterize Jetty IoC XML via the use of the Property element.

  • To configure the default logging mechanism (StdErrLog). You can also plug in other logging frameworks, and also use property files (for example, log4j).

  • As a simple database for login usernames and credentials.

Jetty IoC XML format

To understand the Jetty IoC XML format, consider the following example of an embedded Jetty server instantiated and configured in java:

Jetty IoC XML format allows you to instantiate and configure the exact same server in XML without writing any java code:

In practise, most commonly used Jetty features have XML files that are included in the standard distribution in the etc directory. Thus configuring Jetty is often a matter of just editing existing XML files and altering the property values injected into them.

See an error or something missing? Contribute to this documentation at Github!(Generated: 2015-09-02T01:01:00+00:00)