# Apache Tomcat 8 Configuration Reference (8.5.32) - Overview
Author: Craig R. McClanahan

## Overview

This manual contains reference information about all of the configuration directives that can be included in a `conf/server.xml` file to configure the behavior of the Tomcat Servlet/JSP container. It does not attempt to describe which configuration directives should be used to perform specific tasks - for that, see the various HOW-TO documents on the main index page.

Tomcat configuration files are formatted as schemaless XML; elements and attributes are case-sensitive. Apache Ant-style variable substitution is supported; a system property with the name `propname` may be used in a configuration file using the syntax `${propname}`. All system properties are available including those set using the `-D` syntax, those automatically made available by the JVM and those configured in the `$CATALINA_BASE/conf/catalina.properties` file.

The configuration element descriptions are organized into the following major categories:

- Top Level Elements - `<Server>` is the root element of the entire configuration file, while `<Service>` represents a group of Connectors that is associated with an Engine.
- Connectors - Represent the interface between external clients sending requests to (and receiving responses from) a particular Service.
- Containers - Represent components whose function is to process incoming requests, and create the corresponding responses. An Engine handles all requests for a Service, a Host handles all requests for a particular virtual host, and a Context handles all requests for a specific web application.
- Nested Components - Represent elements that can be nested inside the element for a Container. Some elements can be nested inside any Container, while others can only be nested inside a Context.

For each element, the corresponding documentation follows this general outline:

- Introduction - Overall description of this particular component. There will be a corresponding Java interface (in the `org.apache.catalina` package) that is implemented by one or more standard implementations.
- Attributes - The set of attributes that are legal for this element. Generally, this will be subdivided into Common attributes that are supported by all implementations of the corresponding Java interface, and Standard Implementation attributes that are specific to a particular Java class that implements this interface. The names of required attributes are bolded.
- Nested Components - Enumerates which of the Nested Components can be legally nested within this element.
- Special Features - Describes the configuration of a large variety of special features (specific to each element type) that are supported by the standard implementation of this interface.

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