Top Level Elements
The Context Container
The Context element represents a web
application, which is run within a particular virtual host.
Each web application is based on a Web Application Archive
(WAR) file, or a corresponding directory containing the corresponding
unpacked contents, as described in the Servlet Specification (version
2.2 or later). For more information about web application archives,
you can download the
Specification, and review the Tomcat
Application Developer's Guide.
The web application used to process each HTTP request is selected
by Catalina based on matching the longest possible prefix of the
Request URI against the context path of each defined Context.
Once selected, that Context will select an appropriate servlet to
process the incoming request, according to the servlet mappings defined
in the web application deployment descriptor file (which MUST
be located at
/WEB-INF/web.xml within the web app's
You may define as many Context elements as you
wish, nested within a Host element in
conf/server.xml. Each such Context MUST have a unique
context path, which is defined by the
In addition, you MUST define a Context with a context path equal to
a zero-length string. This Context becomes the default
web application for this virtual host, and is used to process all
requests that do not match any other Context's context path.
In addition to explicitly specified Context elements, there are
several techniques by which Context elements can be created automatically
for you. See
Automatic Application Deployment and
User Web Applications
for more information.
The description below uses the variable name $CATALINA_HOME
to refer to the directory into which you have installed Tomcat 4,
and is the base directory against which most relative paths are
resolved. However, if you have configured Tomcat 4 for multiple
instances by setting a CATALINA_BASE directory, you should use
$CATALINA_BASE instead of $CATALINA_HOME for each of these
All implementations of Context
support the following attributes:
Java class name of the implementation to use. This class must
If not specified, the standard value (defined below) will be used.
true if you want cookies to be used for
session identifier communication if supported by the client (this
is the default). Set to
false if you want to disable
only on URL rewriting by the application.
true if you want calls within this application
ServletContext.getContext() to successfully return a
request dispatcher for other web applications running on this virtual
host. Set to
false (the default) in security
conscious environments, to make
The Document Base (also known as the Context
Root) directory for this web application, or the pathname
to the web application archive file (if this web application is
being executed directly from the WAR file). You may specify
an absolute pathname for this directory or WAR file, or a pathname
that is relative to the
appBase directory of the
true to have explicit settings in this
Context element override any corresponding settings in the
DefaultContext element associated
with our owning Host. By default, settings
in the DefaultContext element will be used.
The context path of this web application, which is
matched against the beginning of each request URI to select the
appropriate web application for processing. All of the context paths
within a particular Host must be unique.
If you specify a context path of an empty string (""), you are
defining the default web application for this Host, which
will process all requests not assigned to other Contexts.
true to allow this context to use container
servlets, like the manager servlet.
true if you want Catalina to monitor classes in
changes, and automatically reload the web application if a change
is detected. This feature is very useful during application
development, but it requires significant runtime overhead and is
not recommended for use on deployed production applications. You
can use the Manager web
application, however, to trigger reloads of deployed applications
true (the default) to have Catalina enable a
InitialContext for this web application that is
compatible with Java2 Enterprise Edition (J2EE) platform
Java class name of the
implementation class that will be used for servlets managed by this
Context. If not specified, a standard default value will be used.
The standard implementation of Context is
It supports the following additional attributes (in addition to the
common attributes listed above):
The level of debugging detail logged by this Engine
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
Pathname to a scratch directory to be provided by this Context
for temporary read-write use by servlets within the associated web
application. This directory will be made visible to servlets in the
web application by a servlet context attribute (of type
javax.servlet.context.tempdir as described in the
Servlet Specification. If not specified, a suitable directory
$CATALINA_HOME/work will be provided.
You can nest at most one instance of the following utility components
by nesting a corresponding element inside your Context
- Loader -
Configure the web application class loader that will be used to load
servlet and bean classes for this web application. Normally, the
default configuration of the class loader will be sufficient.
- Logger -
Configure a logger that will receive
and process all log messages for this Context. This
includes application messages logged via calls to
- Manager -
Configure the session manager that will be used to create, destroy,
and persist HTTP sessions for this web application. Normally, the
default configuration of the session manager will be sufficient.
- Realm -
Configure a realm that will allow its
database of users, and their associated roles, to be utilized solely
for this particular web application. If not specified, this web
application will utilize the Realm associated with the owning
Host or Engine.
- Resources -
Configure the resource manager that will be used to access the static
resources associated with this web application. Normally, the
default configuration of the resource manager will be sufficient.
|Automatic Context Configuration|
If you use the standard Context implementation,
the following configuration steps occur automtically when Catalina
is started, or whenever this web application is reloaded. No special
configuration is required to enable this feature.
- If you have not declared your own Loader
element, a standard web application class loader will be configured.
- If you have not declared your own Manager
element, a standard session manager will be configured.
- If you have not declared your own Resources
element, a standard resources manager will be configured.
- The web application properties listed in
will be processed as defaults for this web application. This is used
to establish default mappings (such as mapping the
extension to the corresponding JSP servlet), and other standard
features that apply to all web applications.
- The web application properties listed in the
/WEB-INF/web.xml resource for this web application
will be processed (if this resource exists).
- If your web application has specified security constraints that might
require user authentication, an appropriate Authenticator that
implements the login method you have selected will be configured.
You can configure named values that will be made visible to the
web application as environment entry resources, by nesting
<Environment> entries inside this element. For
example, you can create an environment entry like this:
<Environment name="maxExemptions" value="10"
This is equivalent to the inclusion of the following element in the
web application deployment descriptor (
but does not require modification of the deployment descriptor
to customize this value.
The valid attributes for an
are as follows:
Optional, human-readable description of this environment entry.
The name of the environment entry to be created, relative to the
Set this to
false if you do not want
<env-entry> for the same environment entry name,
found in the web application deployment descriptor, to override the
value specified here. By default, overrides are allowed.
The fully qualified Java class name expected by the web application
for this environment entry. Must be one of the legal values for
<env-entry-type> in the web application deployment
The parameter value that will be presented to the application
when requested from the JNDI context. This value must be convertable
to the Java type defined by the
This element is used to configure the resource manager (or object
factory) used to return objects when the web application performs a
JNDI lookup operation on the corresponding resource name. You
MUST define resource parameters for every resource name
that is specified by a
<Resource> element inside a
$CATALINA_HOME/conf/server.xml, and/or for every
name declared in a
<resource-env-ref> element in the web application
deployment descriptor, before that resource can be successfully
Resource parameters are defined by name, and the precise set of
parameter names supported depend on the resource manager (or object
factory) you are using - they must match the names of settable JavaBeans
properties on the corresponding factory class. The JNDI implementation
will configure an instance of the specified factory class specified by
calling all the corresponding JavaBeans property setters, and then
making the factory instance available via the JNDI
The resource parameters for a JDBC data source might look something
If you need to specify the Java class name of a factory class for a
particular resource type, use a
factory nested inside the
The valid attributes of a
are as follows:
The name of the resource being configured, relative to the
java:comp/env contxt. This name MUST
match the name of a resource defined by a
referenced in a
<resource-env-ref> element in the web application