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Tomcat web xml reference

According to the Servlet 2.4 specification, every Web application should include a deployment descriptor (web.xml file). This file must be placed in the WEB-INF/ directory of the Web application.

There is also a web.xml file under the $CATALINA_HOME/conf directory. This file is similar to a Web application’s web.xml file. However, this particular web.xml file is used to specify the default properties for all Web applications that are running within this server instance.

Be very careful when making modifications to this file (such as any additions or changes) because they will affect all Web applications running on the same server instance. Note also that other application servers may or may not support a global default web.xml, as this is not a requirement for Servlet 2.4 standard compliance.

Web.xml can be formally validated against a schema:
<web-app xmlns=""
xsi:schemaLocation=" web-app_2_4.xsd"


How to add a new Servlet mapping ?


How to add a parameter to your Context ?

<description>parameter description</description>

String username = getServletContext().getInitParameter("username");
How to flag a web application as clusterable ?


How to add an EJB reference in your web.xml ?

<description>Sample EJB</description>

How to add a reference to an environment variable ?

How to direct errors to error pages ?


How to add a filter to your web.xml ?
<filter-name>Compression Filter</filter-name>

<filter-name>Compression Filter</filter-name>

How to reference a tag lib ?


How to add a Context/Session listener ?


  • Here's an example how to use SessionListeners:
  • Here's an example how to use ContextListeners:

How to secure your application with JAAS ?

<realm-name>Example Form-Based Authentication Area</realm-name>

<display-name>Example Security Constraint</display-name>
<web-resource-name>Protected Area</web-resource-name>






How to add a MIME mapping to your web.xml ?


How to add a reference to a Datasource ?

<!-- JDBC DataSources (java:comp/env/jdbc) -->
<description>The default JDBC datasource</description>

How to configure the session timeout ?


How to add a welcome file list ?



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Tomcat maxThreads configuration

Tomcat maxThreads represents the maximum number of request
processing threads to be created by the HTTPConnector.

<Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol" maxThreads="250" SSLEnabled="true" scheme="https" secure="true" clientAuth="false" sslProtocol="TLS" connectiontimeout="20000"/> This determines the maximum number of simultaneous requests that can be handled. If not specified, this attribute is set to the default value of 200.

How the process works:
At server startup, the HTTP Connector will create a number of processing threads based on the value configured for the minSpareThreads attribute. Each incoming request requires a thread for the duration of that request. If the number of simultaneous requests cannot be handled by the currently available request processing threads, additional threads will be created up to the configured maximu…

Tomcat Websocket example

A WebSocket is a full-duplex communication mechanism that allows both textual and binary messages to be sent between clients and servers, without the HTTP request/response life cycle. WebSockets allow either the client or the server to send a message at any time, providing an asynchronous solution for working with data while the user is performing a task.
Websockets API are included in Tomcat 7 Web server distribution so you don't have to download any extra library:

In this tutorial we will show how to create a WebSocket example using Apache Tomcat and Eclipse.
Start by creating on Eclipse a new Dynamic project named websocket-example:
We will now create a server side class named WebSocketDemo that is going to echo messages from a Javascript client:
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Tomcat Thread Pool configuration

In order to accept incoming requests, Tomcat uses a Thread pool. You can configure two types of Thread Pools: Shared Pool and Dedicated Pool.
A Shared pool as the name inplies, can be shared among various components in Tomcat. So, for example if you have three connectors in your configuration, then you can use a single shared pool to serve requests for all of them. Here is how to configure a shared thread pool:

Open Tomcat's server.xml file and include the Executor definition:

namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/>
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namePrefix="catalina-exec-" maxThreads="200" minSpareThreads="4"/>
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