Apache Tomcat 10 (10.1.34-dev) - Tomcat Web Application Manager How To
Author: Glenn L. Nielsen

## Tomcat Web Application Manager How To

### Table of Contents

- Introduction
- Message
- Manager
- Applications
  1. Start
  2. Stop
  3. Reload
  4. Undeploy
- Deploy
  1. Deploy directory or WAR file located on server
     1. Deploy a Directory or WAR by URL
     2. Deploy a Directory or War from the Host appBase
     3. Deploy using a Context configuration ".xml" file
  2. Upload a WAR file to install
  3. Deployment Notes
  4. Deploy Message
- Diagnostics
  1. Finding memory leaks
- Server Information

### Introduction

In many production environments it is very useful to have the capability to manage your web applications without having to shut down and restart Tomcat. This document is for the HTML web interface to the web application manager.

The interface is divided into six sections:

- Message - Displays success and failure messages.
- Manager - General manager operations like list and help.
- Applications - List of web applications and commands.
- Deploy - Deploying web applications.
- Diagnostics - Identifying potential problems.
- Server Information - Information about the Tomcat server.

### Message

Displays information about the success or failure of the last web application manager command you performed. If it succeeded OK is displayed and may be followed by a success message. If it failed FAIL is displayed followed by an error message. Common failure messages are documented below for each command. The complete list of failure messages for each command can be found in the manager web application documentation.

### Manager

The Manager section has three links:

- List Applications - Redisplay a list of web applications.
- HTML Manager Help - A link to this document.
- Manager Help - A link to the comprehensive Manager App HOW TO.

### Applications

The Applications section lists information about all the installed web applications and provides links for managing them. For each web application the following is displayed:

- Path - The web application context path.
- Display Name - The display name for the web application if it has one configured in its "web.xml" file.
- Running - Whether the web application is running and available (true), or not running and unavailable (false).
- Sessions - The number of active sessions for remote users of this web application. The number of sessions is a link which when submitted displays more details about session usage by the web application in the Message box.
- Commands - Lists all commands which can be performed on the web application. Only those commands which can be performed will be listed as a link which can be submitted. No commands can be performed on the manager web application itself. The following commands can be performed:
  - Start - Start a web application which had been stopped.
  - Stop - Stop a web application which is currently running and make it unavailable.
  - Reload - Reload the web application so that new ".jar" files in `/WEB-INF/lib/` or new classes in `/WEB-INF/classes/` can be used.
  - Undeploy - Stop and then remove this web application from the server.

#### Start

Signal a stopped application to restart, and make itself available again. Stopping and starting is useful, for example, if the database required by your application becomes temporarily unavailable. It is usually better to stop the web application that relies on this database rather than letting users continuously encounter database exceptions.

If this command succeeds, you will see a Message like this:

    OK - Started application at context path /examples

Otherwise, the Message will start with `FAIL` and include an error message. Possible causes for problems include:

- Encountered exception

  An exception was encountered trying to start the web application. Check the Tomcat logs for the details.

- Invalid context path was specified

  The context path must start with a slash character, unless you are referencing the ROOT web application -- in which case the context path must be a zero-length string.

- No context exists for path /foo

  There is no deployed application on the context path that you specified.

- No context path was specified

  The `path` parameter is required.

#### Stop

Signal an existing application to make itself unavailable, but leave it deployed. Any request that comes in while an application is stopped will see an HTTP error 404, and this application will show as "stopped" on a list applications command.

If this command succeeds, you will see a Message like this:

    OK - Stopped application at context path /examples

Otherwise, the Message will start with `FAIL` and include an error message. Possible causes for problems include:

- Encountered exception

  An exception was encountered trying to stop the web application. Check the Tomcat logs for the details.

- Invalid context path was specified

  The context path must start with a slash character, unless you are referencing the ROOT web application -- in which case the context path must be a zero-length string.

- No context exists for path /foo

  There is no deployed application on the context path that you specified.

- No context path was specified

  The `path` parameter is required.

#### Reload

Signal an existing application to shut itself down and reload. This can be useful when the web application context is not reloadable and you have updated classes or property files in the `/WEB-INF/classes` directory or when you have added or updated jar files in the `/WEB-INF/lib` directory.

NOTE: The `/WEB-INF/web.xml` web application configuration file is not checked on a reload; the previous web.xml configuration is used. If you have made changes to your web.xml file you must stop then start the web application.

If this command succeeds, you will see a Message like this:

    OK - Reloaded application at context path /examples

Otherwise, the Message will start with `FAIL` and include an error message. Possible causes for problems include:

- Encountered exception

  An exception was encountered trying to restart the web application. Check the Tomcat logs for the details.

- Invalid context path was specified

  The context path must start with a slash character, unless you are referencing the ROOT web application -- in which case the context path must be a zero-length string.

- No context exists for path /foo

  There is no deployed application on the context path that you specified.

- No context path was specified

  The `path` parameter is required.

- Reload not supported on WAR deployed at path /foo

  Currently, application reloading (to pick up changes to the classes or `web.xml` file) is not supported when a web application is installed directly from a WAR file, which happens when the host is configured to not unpack WAR files. As it only works when the web application is installed from an unpacked directory, if you are using a WAR file, you should `undeploy` and then `deploy` the application again to pick up your changes.

#### Undeploy

WARNING - This command will delete the contents of the web application directory and/or ".war" file if it exists within the `appBase` directory (typically "webapps") for this virtual host . The web application temporary work directory is also deleted. If you simply want to take an application out of service, you should use the `/stop` command instead.

Signal an existing application to gracefully shut itself down, and then remove it from Tomcat (which also makes this context path available for reuse later). This command is the logical opposite of the `/deploy` Ant command, and the related deploy features available in the HTML manager.

If this command succeeds, you will see a Message like this:

    OK - Undeployed application at context path /examples

Otherwise, the Message will start with `FAIL` and include an error message. Possible causes for problems include:

- Encountered exception

  An exception was encountered trying to undeploy the web application. Check the Tomcat logs for the details.

- Invalid context path was specified

  The context path must start with a slash character, unless you are referencing the ROOT web application -- in which case the context path must be a zero-length string.

- No context exists for path /foo

  There is no deployed application on the context path that you specified.

- No context path was specified The `path` parameter is required.

### Deploy

Web applications can be deployed using files or directories located on the Tomcat server or you can upload a web application archive (WAR) file to the server.

To install an application, fill in the appropriate fields for the type of install you want to do and then submit it using the Install button.

#### Deploy directory or WAR file located on server

Deploy and start a new web application, attached to the specified Context Path: (which must not be in use by any other web application). This command is the logical opposite of the Undeploy command.

There are a number of different ways the deploy command can be used.

#### Deploy a Directory or WAR by URL

Install a web application directory or ".war" file located on the Tomcat server. If no Context Path is specified, the directory name or the war file name without the ".war" extension is used as the path. The WAR or Directory URL specifies a URL (including the `file:` scheme) for either a directory or a web application archive (WAR) file. The supported syntax for a URL referring to a WAR file is described on the Javadocs page for the `java.net.JarURLConnection` class. Use only URLs that refer to the entire WAR file.

In this example the web application located in the directory `C:\path\to\foo` on the Tomcat server (running on Windows) is deployed as the web application context named `/footoo`.

    Context Path: /footoo
    WAR or Directory URL: file:C:/path/to/foo

In this example the ".war" file `/path/to/bar.war` on the Tomcat server (running on Unix) is deployed as the web application context named `/bar`. Notice that there is no `path` parameter so the context path defaults to the name of the web application archive file without the ".war" extension.

    WAR or Directory URL: jar:file:/path/to/bar.war!/

#### Deploy a Directory or War from the Host appBase

Install a web application directory or ".war" file located in your Host appBase directory. If no Context Path is specified the directory name or the war file name without the ".war" extension is used as the path.

In this example the web application located in a subdirectory named `foo` in the Host appBase directory of the Tomcat server is deployed as the web application context named `/foo`. Notice that there is no `path` parameter so the context path defaults to the name of the web application directory.

    WAR or Directory URL: foo

In this example the ".war" file `bar.war` located in your Host appBase directory on the Tomcat server is deployed as the web application context named `/bartoo`.

    Context Path: /bartoo
    WAR or Directory URL: bar.war

#### Deploy using a Context configuration ".xml" file

If the Host deployXML flag is set to true, you can install a web application using a Context configuration ".xml" file and an optional ".war" file or web application directory. The Context Path is not used when installing a web application using a context ".xml" configuration file.

A Context configuration ".xml" file can contain valid XML for a web application Context just as if it were configured in your Tomcat `server.xml` configuration file. Here is an example for Tomcat running on Windows:

    <Context path="/foobar" docBase="C:\path\to\application\foobar">
    </Context>

Use of the WAR or Directory URL is optional. When used to select a web application ".war" file or directory it overrides any docBase configured in the context configuration ".xml" file.

Here is an example of installing an application using a Context configuration ".xml" file for Tomcat running on Windows.

    XML Configuration file URL: file:C:/path/to/context.xml

Here is an example of installing an application using a Context configuration ".xml" file and a web application ".war" file located on the server (Tomcat running on Unix).

    XML Configuration file URL: file:/path/to/context.xml
    WAR or Directory URL: jar:file:/path/to/bar.war!/

#### Upload a WAR file to install

Upload a WAR file from your local system and install it into the appBase for your Host. The name of the WAR file without the ".war" extension is used as the context path name.

Use the Browse button to select a WAR file to upload to the server from your local desktop system.

The .WAR file may include Tomcat specific deployment configuration, by including a Context configuration XML file in `/META-INF/context.xml`.

Upload of a WAR file could fail for the following reasons:

- File uploaded must be a .war

  The upload install will only accept files which have the filename extension of ".war".

- War file already exists on server

  If a war file of the same name already exists in your Host's appBase the upload will fail. Either undeploy the existing war file from your Host's appBase or upload the new war file using a different name.

- File upload failed, no file

  The file upload failed, no file was received by the server.

- Install Upload Failed, Exception:

  The war file upload or install failed with a Java Exception. The exception message will be listed.

#### Deployment Notes

If the Host is configured with unpackWARs=true and you install a war file, the war will be unpacked into a directory in your Host appBase directory.

If the application war or directory is deployed in your Host appBase directory and either the Host is configured with autoDeploy=true the Context path must match the directory name or war file name without the ".war" extension.

For security when untrusted users can manage web applications, the Host deployXML flag can be set to false. This prevents untrusted users from installing web applications using a configuration XML file and also prevents them from installing application directories or ".war" files located outside of their Host appBase.

#### Deploy Message

If deployment and startup is successful, you will receive a Message like this:

    OK - Deployed application at context path /foo

Otherwise, the Message will start with `FAIL` and include an error message. Possible causes for problems include:

- Application already exists at path /foo

  The context paths for all currently running web applications must be unique. Therefore, you must either undeploy the existing web application using this context path, or choose a different context path for the new one.

- Document base does not exist or is not a readable directory

  The URL specified by the WAR or Directory URL: field must identify a directory on this server that contains the "unpacked" version of a web application, or the absolute URL of a web application archive (WAR) file that contains this application. Correct the value entered for the WAR or Directory URL: field.

- Encountered exception

  An exception was encountered trying to start the new web application. Check the Tomcat logs for the details, but likely explanations include problems parsing your `/WEB-INF/web.xml` file, or missing classes encountered when initializing application event listeners and filters.

- Invalid application URL was specified

  The URL for the WAR or Directory URL: field that you specified was not valid. Such URLs must start with `file:`, and URLs for a WAR file must end in ".war".

- Invalid context path was specified

  The context path must start with a slash character, unless you are referencing the ROOT web application -- in which case the context path must be a "/" string.

- Context path must match the directory or WAR file name:

  If the application war or directory is deployed in your Host appBase directory and either the Host is configured with autoDeploy=true the Context path must match the directory name or war file name without the ".war" extension.

- Only web applications in the Host web application directory can be deployed

  If the Host deployXML flag is set to false this error will happen if an attempt is made to install a web application directory or ".war" file outside of the Host appBase directory.

### Diagnostics

#### Finding memory leaks

The find leaks diagnostic triggers a full garbage collection. It should be used with extreme caution on production systems.

The find leaks diagnostic attempts to identify web applications that have caused memory leaks when they were stopped, reloaded or undeployed. Results should always be confirmed with a profiler. The diagnostic uses additional functionality provided by the StandardHost implementation. It will not work if a custom host is used that does not extend StandardHost.

This diagnostic will list context paths for the web applications that were stopped, reloaded or undeployed, but which classes from the previous runs are still present in memory, thus being a memory leak. If an application has been reloaded several times, it may be listed several times.

Explicitly triggering a full garbage collection from Java code is documented to be unreliable. Furthermore, depending on the JVM used, there are options to disable explicit GC triggering, like `-XX:+DisableExplicitGC`. If you want to make sure, that the diagnostics were successfully running a full GC, you will need to check using tools like GC logging, JConsole or similar.

### Server Information

This section displays information about Tomcat, the operating system of the server Tomcat is hosted on, the Java Virtual Machine Tomcat is running in, the primary host name of the server (may not be the host name used to access Tomcat) and the primary IP address of the server (may not be the IP address used to access Tomcat).