Host (Apache Tomcat 9.0.120 API Documentation)
Description: declaration: package: org.apache.catalina, interface: Host

# Interface Host

All Superinterfaces:
  `Container, Lifecycle`

All Known Implementing Classes:
  `StandardHost`

public interface Host extends Container
A Host is a Container that represents a virtual host in the Catalina servlet engine. It is useful in the following types of scenarios:

- You wish to use Interceptors that see every single request processed by this particular virtual host.
- You wish to run Catalina in with a standalone HTTP connector, but still want support for multiple virtual hosts.

In general, you would not use a Host when deploying Catalina connected to a web server (such as Apache), because the Connector will have utilized the web server's facilities to determine which Context (or perhaps even which Wrapper) should be utilized to process this request.

The parent Container attached to a Host is generally an Engine, but may be some other implementation, or may be omitted if it is not necessary.

The child containers attached to a Host are generally implementations of Context (representing an individual servlet context).

- ## Nested Class Summary

  ### Nested classes/interfaces inherited from interface Lifecycle

  `Lifecycle.SingleUse`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `ADD_ALIAS_EVENT`
  The ContainerEvent event type sent when a new alias is added by `addAlias()`.
  `static final String`
  `REMOVE_ALIAS_EVENT`
  The ContainerEvent event type sent when an old alias is removed by `removeAlias()`.

  ### Fields inherited from interface Container

  `ADD_CHILD_EVENT, ADD_VALVE_EVENT, REMOVE_CHILD_EVENT, REMOVE_VALVE_EVENT`

  ### Fields inherited from interface Lifecycle

  `AFTER_DESTROY_EVENT, AFTER_INIT_EVENT, AFTER_START_EVENT, AFTER_STOP_EVENT, BEFORE_DESTROY_EVENT, BEFORE_INIT_EVENT, BEFORE_START_EVENT, BEFORE_STOP_EVENT, CONFIGURE_START_EVENT, CONFIGURE_STOP_EVENT, PERIODIC_EVENT, START_EVENT, STOP_EVENT`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addAlias(String alias)`
  Add an alias name that should be mapped to this same Host.
  `String[]`
  `findAliases()`
  Get the array of alias names for this Host.
  `String`
  `getAppBase()`
  Get the application root for this Host.
  `File`
  `getAppBaseFile()`
  Get an absolute `File` for the appBase of this Host.
  `boolean`
  `getAutoDeploy()`
  `File`
  `getConfigBaseFile()`
  Get the default configuration path of this Host.
  `String`
  `getConfigClass()`
  Get the Java class name of the context configuration class for new web applications.
  `boolean`
  `getCreateDirs()`
  Returns `true` if the Host will attempt to create directories for appBase and xmlBase unless they already exist.
  `String`
  `getDeployIgnore()`
  Get the regular expression that defines the files and directories in the host's appBase that will be ignored by the automatic deployment process.
  `Pattern`
  `getDeployIgnorePattern()`
  Get the compiled regular expression that defines the files and directories in the host's appBase that will be ignored by the automatic deployment process.
  `boolean`
  `getDeployOnStartup()`
  Get the value of the deploy on startup flag.
  `ExecutorService`
  `getStartStopExecutor()`
  Get the executor that is used for starting and stopping contexts.
  `boolean`
  `getUndeployOldVersions()`
  Get whether the Host is configured to automatically undeploy old versions of applications deployed using parallel deployment.
  `String`
  `getXmlBase()`
  Get the XML root for this Host.
  `void`
  `removeAlias(String alias)`
  Remove the specified alias name from the aliases for this Host.
  `void`
  `setAppBase(String appBase)`
  Set the application root for this Host.
  `void`
  `setAutoDeploy(boolean autoDeploy)`
  Set the auto deploy flag value for this host.
  `void`
  `setConfigClass(String configClass)`
  Set the Java class name of the context configuration class for new web applications.
  `void`
  `setCreateDirs(boolean createDirs)`
  Should the Host attempt to create directories for xmlBase and appBase upon startup.
  `void`
  `setDeployIgnore(String deployIgnore)`
  Set the regular expression that defines the files and directories in the host's appBase that will be ignored by the automatic deployment process.
  `void`
  `setDeployOnStartup(boolean deployOnStartup)`
  Set the deploy on startup flag value for this host.
  `void`
  `setUndeployOldVersions(boolean undeployOldVersions)`
  Set to `true` if the Host should automatically undeploy old versions of applications deployed using parallel deployment.
  `void`
  `setXmlBase(String xmlBase)`
  Set the Xml root for this Host.

  ### Methods inherited from interface Container

  `addChild, addContainerListener, addPropertyChangeListener, backgroundProcess, findChild, findChildren, findContainerListeners, fireContainerEvent, getAccessLog, getBackgroundProcessorDelay, getCatalinaBase, getCatalinaHome, getCluster, getDomain, getLogger, getLogName, getMBeanKeyProperties, getName, getObjectName, getParent, getParentClassLoader, getPipeline, getRealm, getStartStopThreads, logAccess, removeChild, removeContainerListener, removePropertyChangeListener, setBackgroundProcessorDelay, setCluster, setName, setParent, setParentClassLoader, setRealm, setStartStopThreads`

  ### Methods inherited from interface Lifecycle

  `addLifecycleListener, destroy, findLifecycleListeners, getState, getStateName, init, removeLifecycleListener, start, stop`

- ## Field Details

  - ### ADD_ALIAS_EVENT

    static final String ADD_ALIAS_EVENT
    The ContainerEvent event type sent when a new alias is added by `addAlias()`.
    See Also:
      - Constant Field Values

  - ### REMOVE_ALIAS_EVENT

    static final String REMOVE_ALIAS_EVENT
    The ContainerEvent event type sent when an old alias is removed by `removeAlias()`.
    See Also:
      - Constant Field Values

- ## Method Details

  - ### getXmlBase

    String getXmlBase()
    Get the XML root for this Host. This can be an absolute pathname or a relative pathname. If null, the base path defaults to ${catalina.base}/conf/<engine name>/<host name> directory.
    Returns:
      the XML root

  - ### setXmlBase

    void setXmlBase(String xmlBase)
    Set the Xml root for this Host. This can be an absolute pathname or a relative pathname. If null, the base path defaults to ${catalina.base}/conf/<engine name>/<host name> directory
    Parameters:
      `xmlBase` - The new XML root

  - ### getConfigBaseFile

    File getConfigBaseFile()
    Get the default configuration path of this Host. The file will be canonical if possible.
    Returns:
      the configuration base file

  - ### getAppBase

    String getAppBase()
    Get the application root for this Host. This can be an absolute pathname, a relative pathname, or a URL.
    Returns:
      the application root

  - ### getAppBaseFile

    File getAppBaseFile()
    Get an absolute `File` for the appBase of this Host. The file will be canonical if possible. There is no guarantee that the appBase exists.
    Returns:
      the application base file

  - ### setAppBase

    void setAppBase(String appBase)
    Set the application root for this Host. This can be an absolute pathname, a relative pathname, or a URL.
    Parameters:
      `appBase` - The new application root

  - ### getAutoDeploy

    boolean getAutoDeploy()
    Returns:
      the value of the auto deploy flag. If true, it indicates that this host's child webapps should be discovered and automatically deployed dynamically.

  - ### setAutoDeploy

    void setAutoDeploy(boolean autoDeploy)
    Set the auto deploy flag value for this host.
    Parameters:
      `autoDeploy` - The new auto deploy flag

  - ### getConfigClass

    String getConfigClass()
    Get the Java class name of the context configuration class for new web applications.
    Returns:
      the context configuration class name

  - ### setConfigClass

    void setConfigClass(String configClass)
    Set the Java class name of the context configuration class for new web applications.
    Parameters:
      `configClass` - The new context configuration class

  - ### getDeployOnStartup

    boolean getDeployOnStartup()
    Get the value of the deploy on startup flag. If true, it indicates that this host's child webapps should be discovered and automatically deployed.
    Returns:
      the deploy on startup flag

  - ### setDeployOnStartup

    void setDeployOnStartup(boolean deployOnStartup)
    Set the deploy on startup flag value for this host.
    Parameters:
      `deployOnStartup` - The new deploy on startup flag

  - ### getDeployIgnore

    String getDeployIgnore()
    Get the regular expression that defines the files and directories in the host's appBase that will be ignored by the automatic deployment process.
    Returns:
      the deploy ignore regular expression

  - ### getDeployIgnorePattern

    Pattern getDeployIgnorePattern()
    Get the compiled regular expression that defines the files and directories in the host's appBase that will be ignored by the automatic deployment process.
    Returns:
      the compiled deploy ignore pattern

  - ### setDeployIgnore

    void setDeployIgnore(String deployIgnore)
    Set the regular expression that defines the files and directories in the host's appBase that will be ignored by the automatic deployment process.
    Parameters:
      `deployIgnore` - A regular expression matching file names

  - ### getStartStopExecutor

    ExecutorService getStartStopExecutor()
    Get the executor that is used for starting and stopping contexts. This is primarily for use by components deploying contexts that want to do this in a multithreaded manner.
    Returns:
      the start/stop executor

  - ### getCreateDirs

    boolean getCreateDirs()
    Returns `true` if the Host will attempt to create directories for appBase and xmlBase unless they already exist.
    Returns:
      true if the Host will attempt to create directories

  - ### setCreateDirs

    void setCreateDirs(boolean createDirs)
    Should the Host attempt to create directories for xmlBase and appBase upon startup.
    Parameters:
      `createDirs` - The new value for this flag

  - ### getUndeployOldVersions

    boolean getUndeployOldVersions()
    Get whether the Host is configured to automatically undeploy old versions of applications deployed using parallel deployment. This only takes effect if `getAutoDeploy()` also returns `true`.
    Returns:
      the undeploy old versions flag

  - ### setUndeployOldVersions

    void setUndeployOldVersions(boolean undeployOldVersions)
    Set to `true` if the Host should automatically undeploy old versions of applications deployed using parallel deployment. This only takes effect if `getAutoDeploy()` returns `true`.
    Parameters:
      `undeployOldVersions` - The new value for this flag

  - ### addAlias

    void addAlias(String alias)
    Add an alias name that should be mapped to this same Host.
    Parameters:
      `alias` - The alias to be added

  - ### findAliases

    String[] findAliases()
    Get the array of alias names for this Host. If none are defined, a zero length array is returned.
    Returns:
      the array of alias names

  - ### removeAlias

    void removeAlias(String alias)
    Remove the specified alias name from the aliases for this Host.
    Parameters:
      `alias` - Alias name to be removed