# Interface ServletContext

public interface ServletContext
Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.

There is one context per "web application" per Java Virtual Machine. (A "web application" is a collection of servlets and content installed under a specific subset of the server's URL namespace such as `/catalog` and possibly installed via a `.war` file.)

In the case of a web application marked "distributed" in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information won't be truly global). Use an external resource like a database instead.

The `ServletContext` object is contained within the `ServletConfig` object, which the Web server provides the servlet when the servlet is initialized.

See Also:
  - `Servlet.getServletConfig()`
  - `ServletConfig.getServletContext()`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `ORDERED_LIBS`
  The name of the ServletContext attribute that holds the ordered list of web fragments for this web application.
  `static final String`
  `TEMPDIR`
  The name of the ServletContext attribute that holds the temporary file location for the web application.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `FilterRegistration.Dynamic`
  `addFilter(String filterName, Class<? extends Filter> filterClass)`
  Add filter to context.
  `FilterRegistration.Dynamic`
  `addFilter(String filterName, String className)`
  Add filter to context.
  `FilterRegistration.Dynamic`
  `addFilter(String filterName, Filter filter)`
  Add filter to context.
  `ServletRegistration.Dynamic`
  `addJspFile(String jspName, String jspFile)`
  Add a JSP to the context.
  `void`
  `addListener(Class<? extends EventListener> listenerClass)`
  TODO SERVLET3 - Add comments
  `void`
  `addListener(String className)`
  TODO SERVLET3 - Add comments
  `<T extends EventListener>
  void`
  `addListener(T t)`
  TODO SERVLET3 - Add comments
  `ServletRegistration.Dynamic`
  `addServlet(String servletName, Class<? extends Servlet> servletClass)`
  Add servlet to the context.
  `ServletRegistration.Dynamic`
  `addServlet(String servletName, String className)`
  Register a servlet implementation for use in this ServletContext.
  `ServletRegistration.Dynamic`
  `addServlet(String servletName, Servlet servlet)`
  Register a servlet instance for use in this ServletContext.
  `<T extends Filter>
  T`
  `createFilter(Class<T> c)`
  Create a Filter instance using the given class.
  `<T extends EventListener>
  T`
  `createListener(Class<T> c)`
  TODO SERVLET3 - Add comments
  `<T extends Servlet>
  T`
  `createServlet(Class<T> c)`
  Create an Servlet instance using the given class.
  `void`
  `declareRoles(String... roleNames)`
  Add to the declared roles for this ServletContext.
  `Object`
  `getAttribute(String name)`
  Returns the servlet container attribute with the given name, or `null` if there is no attribute by that name.
  `Enumeration<String>`
  `getAttributeNames()`
  Returns an `Enumeration` containing the attribute names available within this servlet context.
  `ClassLoader`
  `getClassLoader()`
  Get the web application class loader associated with this ServletContext.
  `ServletContext`
  `getContext(String uripath)`
  Returns a `ServletContext` object that corresponds to a specified URL on the server.
  `String`
  `getContextPath()`
  Return the main path associated with this context.
  `Set<SessionTrackingMode>`
  `getDefaultSessionTrackingModes()`
  Obtains the default session tracking modes for this web application.
  `int`
  `getEffectiveMajorVersion()`
  Obtain the major version of the servlet specification for which this web application is implemented.
  `int`
  `getEffectiveMinorVersion()`
  Obtain the minor version of the servlet specification for which this web application is implemented.
  `Set<SessionTrackingMode>`
  `getEffectiveSessionTrackingModes()`
  Obtains the currently enabled session tracking modes for this web application.
  `FilterRegistration`
  `getFilterRegistration(String filterName)`
  TODO SERVLET3 - Add comments
  `Map<String, ? extends FilterRegistration>`
  `getFilterRegistrations()`
  `String`
  `getInitParameter(String name)`
  Returns a `String` containing the value of the named context-wide initialization parameter, or `null` if the parameter does not exist.
  `Enumeration<String>`
  `getInitParameterNames()`
  Returns the names of the context's initialization parameters as an `Enumeration` of `String` objects, or an empty `Enumeration` if the context has no initialization parameters.
  `JspConfigDescriptor`
  `getJspConfigDescriptor()`
  `int`
  `getMajorVersion()`
  Returns the major version of the Java Servlet API that this servlet container supports.
  `String`
  `getMimeType(String file)`
  Returns the MIME type of the specified file, or `null` if the MIME type is not known.
  `int`
  `getMinorVersion()`
  Returns the minor version of the Servlet API that this servlet container supports.
  `RequestDispatcher`
  `getNamedDispatcher(String name)`
  Returns a `RequestDispatcher` object that acts as a wrapper for the named servlet.
  `String`
  `getRealPath(String path)`
  Returns a `String` containing the real path for a given virtual path.
  `String`
  `getRequestCharacterEncoding()`
  Get the default character encoding for reading request bodies.
  `RequestDispatcher`
  `getRequestDispatcher(String path)`
  Returns a `RequestDispatcher` object that acts as a wrapper for the resource located at the given path.
  `URL`
  `getResource(String path)`
  Returns a URL to the resource that is mapped to a specified path.
  `InputStream`
  `getResourceAsStream(String path)`
  Returns the resource located at the named path as an `InputStream` object.
  `Set<String>`
  `getResourcePaths(String path)`
  Returns a directory-like listing of all the paths to resources within the web application whose longest sub-path matches the supplied path argument.
  `String`
  `getResponseCharacterEncoding()`
  Get the default character encoding for writing response bodies.
  `String`
  `getServerInfo()`
  Returns the name and version of the servlet container on which the servlet is running.
  `Servlet`
  `getServlet(String name)`
  Deprecated.
  As of Java Servlet API 2.1, with no direct replacement.
  `String`
  `getServletContextName()`
  Returns the name of this web application corresponding to this ServletContext as specified in the deployment descriptor for this web application by the display-name element.
  `Enumeration<String>`
  `getServletNames()`
  Deprecated.
  As of Java Servlet API 2.1, with no replacement.
  `ServletRegistration`
  `getServletRegistration(String servletName)`
  Obtain the details of the named servlet.
  `Map<String, ? extends ServletRegistration>`
  `getServletRegistrations()`
  Obtain a Map of servlet names to servlet registrations for all servlets registered with this context.
  `Enumeration<Servlet>`
  `getServlets()`
  Deprecated.
  As of Java Servlet API 2.0, with no replacement.
  `SessionCookieConfig`
  `getSessionCookieConfig()`
  `int`
  `getSessionTimeout()`
  Get the default session timeout.
  `String`
  `getVirtualServerName()`
  Get the primary name of the virtual host on which this context is deployed.
  `void`
  `log(Exception exception, String msg)`
  Deprecated.
  As of Java Servlet API 2.1, use `log(String message, Throwable throwable)` instead.
  `void`
  `log(String msg)`
  Writes the specified message to a servlet log file, usually an event log.
  `void`
  `log(String message, Throwable throwable)`
  Writes an explanatory message and a stack trace for a given `Throwable` exception to the servlet log file.
  `void`
  `removeAttribute(String name)`
  Removes the attribute with the given name from the servlet context.
  `void`
  `setAttribute(String name, Object object)`
  Binds an object to a given attribute name in this servlet context.
  `boolean`
  `setInitParameter(String name, String value)`
  Set the given initialisation parameter to the given value.
  `void`
  `setRequestCharacterEncoding(String encoding)`
  Set the default character encoding to use for reading request bodies.
  `void`
  `setResponseCharacterEncoding(String encoding)`
  Set the default character encoding to use for writing response bodies.
  `void`
  `setSessionTimeout(int sessionTimeout)`
  Set the default session timeout.
  `void`
  `setSessionTrackingModes(Set<SessionTrackingMode> sessionTrackingModes)`
  Configures the available session tracking modes for this web application.

- ## Field Details

  - ### TEMPDIR

    static final String TEMPDIR
    The name of the ServletContext attribute that holds the temporary file location for the web application.
    See Also:
      - Constant Field Values

  - ### ORDERED_LIBS

    static final String ORDERED_LIBS
    The name of the ServletContext attribute that holds the ordered list of web fragments for this web application.
    Since:
      Servlet 3.0
    See Also:
      - Constant Field Values

- ## Method Details

  - ### getContextPath

    String getContextPath()
    Return the main path associated with this context.
    Returns:
      The main context path
    Since:
      Servlet 2.5

  - ### getContext

    ServletContext getContext(String uripath)
    Returns a `ServletContext` object that corresponds to a specified URL on the server.

    This method allows servlets to gain access to the context for various parts of the server, and as needed obtain `RequestDispatcher` objects from the context. The given path must be begin with "/", is interpreted relative to the server's document root and is matched against the context roots of other web applications hosted on this container.

    In a security conscious environment, the servlet container may return `null` for a given URL.

    Parameters:
      `uripath` - a `String` specifying the context path of another web application in the container.
    Returns:
      the `ServletContext` object that corresponds to the named URL, or null if either none exists or the container wishes to restrict this access.
    See Also:
      - `RequestDispatcher`

  - ### getMajorVersion

    int getMajorVersion()
    Returns the major version of the Java Servlet API that this servlet container supports. All implementations that comply with Version 4.0 must have this method return the integer 4.
    Returns:
      4

  - ### getMinorVersion

    int getMinorVersion()
    Returns the minor version of the Servlet API that this servlet container supports. All implementations that comply with Version 4.0 must have this method return the integer 0.
    Returns:
      0

  - ### getEffectiveMajorVersion

    int getEffectiveMajorVersion()
    Obtain the major version of the servlet specification for which this web application is implemented.
    Returns:
      The major version declared in web.xml
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getEffectiveMinorVersion

    int getEffectiveMinorVersion()
    Obtain the minor version of the servlet specification for which this web application is implemented.
    Returns:
      The minor version declared in web.xml
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getMimeType

    String getMimeType(String file)
    Returns the MIME type of the specified file, or `null` if the MIME type is not known. The MIME type is determined by the configuration of the servlet container, and may be specified in a web application deployment descriptor. Common MIME types are `"text/html"` and `"image/gif"`.
    Parameters:
      `file` - a `String` specifying the name of a file
    Returns:
      a `String` specifying the file's MIME type

  - ### getResourcePaths

    Set<String> getResourcePaths(String path)
    Returns a directory-like listing of all the paths to resources within the web application whose longest sub-path matches the supplied path argument. Paths indicating subdirectory paths end with a '/'. The returned paths are all relative to the root of the web application and have a leading '/'. For example, for a web application containing
    /welcome.html
    /catalog/index.html
    /catalog/products.html
    /catalog/offers/books.html
    /catalog/offers/music.html
    /customer/login.jsp
    /WEB-INF/web.xml
    /WEB-INF/classes/com.acme.OrderServlet.class,
    getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}
    getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.
    Parameters:
      `path` - the partial path used to match the resources, which must start with a /
    Returns:
      a Set containing the directory listing, or null if there are no resources in the web application whose path begins with the supplied path.
    Since:
      Servlet 2.3

  - ### getResource

    URL getResource(String path) throws MalformedURLException
    Returns a URL to the resource that is mapped to a specified path. The path must begin with a "/" and is interpreted as relative to the current context root.

    This method allows the servlet container to make a resource available to servlets from any source. Resources can be located on a local or remote file system, in a database, or in a `.war` file.

    The servlet container must implement the URL handlers and `URLConnection` objects that are necessary to access the resource.

    This method returns `null` if no resource is mapped to the pathname.

    Some containers may allow writing to the URL returned by this method using the methods of the URL class.

    The resource content is returned directly, so be aware that requesting a `.jsp` page returns the JSP source code. Use a `RequestDispatcher` instead to include results of an execution.

    This method has a different purpose than `java.lang.Class.getResource`, which looks up resources based on a class loader. This method does not use class loaders.

    Parameters:
      `path` - a `String` specifying the path to the resource
    Returns:
      the resource located at the named path, or `null` if there is no resource at that path
    Throws:
      `MalformedURLException` - if the pathname is not given in the correct form

  - ### getResourceAsStream

    InputStream getResourceAsStream(String path)
    Returns the resource located at the named path as an `InputStream` object.

    The data in the `InputStream` can be of any type or length. The path must be specified according to the rules given in `getResource`. This method returns `null` if no resource exists at the specified path.

    Meta-information such as content length and content type that is available via `getResource` method is lost when using this method.

    The servlet container must implement the URL handlers and `URLConnection` objects necessary to access the resource.

    This method is different from `java.lang.Class.getResourceAsStream`, which uses a class loader. This method allows servlet containers to make a resource available to a servlet from any location, without using a class loader.

    Parameters:
      `path` - a `String` specifying the path to the resource
    Returns:
      the `InputStream` returned to the servlet, or `null` if no resource exists at the specified path

  - ### getRequestDispatcher

    RequestDispatcher getRequestDispatcher(String path)
    Returns a `RequestDispatcher` object that acts as a wrapper for the resource located at the given path. A `RequestDispatcher` object can be used to forward a request to the resource or to include the resource in a response. The resource can be dynamic or static.

    The pathname must begin with a "/" and is interpreted as relative to the current context root. Use `getContext` to obtain a `RequestDispatcher` for resources in foreign contexts. This method returns `null` if the `ServletContext` cannot return a `RequestDispatcher`.

    Parameters:
      `path` - a `String` specifying the pathname to the resource
    Returns:
      a `RequestDispatcher` object that acts as a wrapper for the resource at the specified path, or `null` if the `ServletContext` cannot return a `RequestDispatcher`
    See Also:
      - `RequestDispatcher`
      - `getContext(java.lang.String)`

  - ### getNamedDispatcher

    RequestDispatcher getNamedDispatcher(String name)
    Returns a `RequestDispatcher` object that acts as a wrapper for the named servlet.

    Servlets (and JSP pages also) may be given names via server administration or via a web application deployment descriptor. A servlet instance can determine its name using `ServletConfig.getServletName()`.

    This method returns `null` if the `ServletContext` cannot return a `RequestDispatcher` for any reason.

    Parameters:
      `name` - a `String` specifying the name of a servlet to wrap
    Returns:
      a `RequestDispatcher` object that acts as a wrapper for the named servlet, or `null` if the `ServletContext` cannot return a `RequestDispatcher`
    See Also:
      - `RequestDispatcher`
      - `getContext(java.lang.String)`
      - `ServletConfig.getServletName()`

  - ### getServlet

    @Deprecated Servlet getServlet(String name) throws ServletException
    Deprecated.
    As of Java Servlet API 2.1, with no direct replacement.
    Do not use. This method was originally defined to retrieve a servlet from a `ServletContext`. In this version, this method always returns `null` and remains only to preserve binary compatibility. This method will be permanently removed in a future version of the Java Servlet API.

    In lieu of this method, servlets can share information using the `ServletContext` class and can perform shared business logic by invoking methods on common non-servlet classes.

    Parameters:
      `name` - Not used
    Returns:
      Always `null`
    Throws:
      `ServletException` - never

  - ### getServlets

    @Deprecated Enumeration<Servlet> getServlets()
    Deprecated.
    As of Java Servlet API 2.0, with no replacement.
    Do not use. This method was originally defined to return an `Enumeration` of all the servlets known to this servlet context. In this version, this method always returns an empty enumeration and remains only to preserve binary compatibility. This method will be permanently removed in a future version of the Java Servlet API.
    Returns:
      Always and empty Enumeration

  - ### getServletNames

    @Deprecated Enumeration<String> getServletNames()
    Deprecated.
    As of Java Servlet API 2.1, with no replacement.
    Do not use. This method was originally defined to return an `Enumeration` of all the servlet names known to this context. In this version, this method always returns an empty `Enumeration` and remains only to preserve binary compatibility. This method will be permanently removed in a future version of the Java Servlet API.
    Returns:
      Always and empty Enumeration

  - ### log

    void log(String msg)
    Writes the specified message to a servlet log file, usually an event log. The name and type of the servlet log file is specific to the servlet container.
    Parameters:
      `msg` - a `String` specifying the message to be written to the log file

  - ### log

    @Deprecated void log(Exception exception, String msg)
    Deprecated.
    As of Java Servlet API 2.1, use `log(String message, Throwable throwable)` instead.

    This method was originally defined to write an exception's stack trace and an explanatory error message to the servlet log file.

    Do not use.
    Parameters:
      `exception` - The exception to log
      `msg` - The message to log with the exception

  - ### log

    void log(String message, Throwable throwable)
    Writes an explanatory message and a stack trace for a given `Throwable` exception to the servlet log file. The name and type of the servlet log file is specific to the servlet container, usually an event log.
    Parameters:
      `message` - a `String` that describes the error or exception
      `throwable` - the `Throwable` error or exception

  - ### getRealPath

    String getRealPath(String path)
    Returns a `String` containing the real path for a given virtual path. For example, the path "/index.html" returns the absolute file path on the server's filesystem would be served by a request for "http://host/contextPath/index.html", where contextPath is the context path of this ServletContext..

    The real path returned will be in a form appropriate to the computer and operating system on which the servlet container is running, including the proper path separators. This method returns `null` if the servlet container cannot translate the virtual path to a real path for any reason (such as when the content is being made available from a `.war` archive).

    Parameters:
      `path` - a `String` specifying a virtual path
    Returns:
      a `String` specifying the real path, or null if the translation cannot be performed

  - ### getServerInfo

    String getServerInfo()
    Returns the name and version of the servlet container on which the servlet is running.

    The form of the returned string is servername/versionnumber. For example, the JavaServer Web Development Kit may return the string `JavaServer Web Dev Kit/1.0`.

    The servlet container may return other optional information after the primary string in parentheses, for example, `JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)`.

    Returns:
      a `String` containing at least the servlet container name and version number

  - ### getInitParameter

    String getInitParameter(String name)
    Returns a `String` containing the value of the named context-wide initialization parameter, or `null` if the parameter does not exist.

    This method can make available configuration information useful to an entire "web application". For example, it can provide a web site administrator's email address or the name of a system that holds critical data.

    Parameters:
      `name` - a `String` containing the name of the parameter whose value is requested
    Returns:
      a `String` containing the value of the initialization parameter
    Throws:
      `NullPointerException` - If the provided parameter name is `null`
    See Also:
      - `ServletConfig.getInitParameter(java.lang.String)`

  - ### getInitParameterNames

    Enumeration<String> getInitParameterNames()
    Returns the names of the context's initialization parameters as an `Enumeration` of `String` objects, or an empty `Enumeration` if the context has no initialization parameters.
    Returns:
      an `Enumeration` of `String` objects containing the names of the context's initialization parameters
    See Also:
      - `ServletConfig.getInitParameter(java.lang.String)`

  - ### setInitParameter

    boolean setInitParameter(String name, String value)
    Set the given initialisation parameter to the given value.
    Parameters:
      `name` - Name of initialisation parameter
      `value` - Value for initialisation parameter
    Returns:
      `true` if the call succeeds or `false` if the call fails because an initialisation parameter with the same name has already been set
    Throws:
      `IllegalStateException` - If initialisation of this ServletContext has already completed
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `NullPointerException` - If the provided parameter name is `null`
    Since:
      Servlet 3.0

  - ### getAttribute

    Object getAttribute(String name)
    Returns the servlet container attribute with the given name, or `null` if there is no attribute by that name. An attribute allows a servlet container to give the servlet additional information not already provided by this interface. See your server documentation for information about its attributes. A list of supported attributes can be retrieved using `getAttributeNames`.

    The attribute is returned as a `java.lang.Object` or some subclass. Attribute names should follow the same convention as package names. The Java Servlet API specification reserves names matching `java.*`, `javax.*`, and `sun.*`.

    Parameters:
      `name` - a `String` specifying the name of the attribute
    Returns:
      an `Object` containing the value of the attribute, or `null` if no attribute exists matching the given name
    Throws:
      `NullPointerException` - If the provided attribute name is `null`
    See Also:
      - `getAttributeNames()`

  - ### getAttributeNames

    Enumeration<String> getAttributeNames()
    Returns an `Enumeration` containing the attribute names available within this servlet context. Use the `getAttribute(java.lang.String)` method with an attribute name to get the value of an attribute.
    Returns:
      an `Enumeration` of attribute names
    See Also:
      - `getAttribute(java.lang.String)`

  - ### setAttribute

    void setAttribute(String name, Object object)
    Binds an object to a given attribute name in this servlet context. If the name specified is already used for an attribute, this method will replace the attribute with the new to the new attribute.

    If listeners are configured on the `ServletContext` the container notifies them accordingly.

    If a null value is passed, the effect is the same as calling `removeAttribute()`.

    Attribute names should follow the same convention as package names. The Java Servlet API specification reserves names matching `java.*`, `javax.*`, and `sun.*`.

    Parameters:
      `name` - a `String` specifying the name of the attribute
      `object` - an `Object` representing the attribute to be bound
    Throws:
      `NullPointerException` - If the provided attribute name is `null`

  - ### removeAttribute

    void removeAttribute(String name)
    Removes the attribute with the given name from the servlet context. After removal, subsequent calls to `getAttribute(java.lang.String)` to retrieve the attribute's value will return `null`.

    If listeners are configured on the `ServletContext` the container notifies them accordingly.

    Parameters:
      `name` - a `String` specifying the name of the attribute to be removed

  - ### getServletContextName

    String getServletContextName()
    Returns the name of this web application corresponding to this ServletContext as specified in the deployment descriptor for this web application by the display-name element.
    Returns:
      The name of the web application or null if no name has been declared in the deployment descriptor.
    Since:
      Servlet 2.3

  - ### addServlet

    ServletRegistration.Dynamic addServlet(String servletName, String className)
    Register a servlet implementation for use in this ServletContext.
    Parameters:
      `servletName` - The name of the servlet to register
      `className` - The implementation class for the servlet
    Returns:
      The registration object that enables further configuration
    Throws:
      `IllegalStateException` - If the context has already been initialised
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addServlet

    ServletRegistration.Dynamic addServlet(String servletName, Servlet servlet)
    Register a servlet instance for use in this ServletContext.
    Parameters:
      `servletName` - The name of the servlet to register
      `servlet` - The Servlet instance to register
    Returns:
      The registration object that enables further configuration
    Throws:
      `IllegalStateException` - If the context has already been initialised
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addServlet

    ServletRegistration.Dynamic addServlet(String servletName, Class<? extends Servlet> servletClass)
    Add servlet to the context.
    Parameters:
      `servletName` - Name of servlet to add
      `servletClass` - Class of servlet to add
    Returns:
      `null` if the servlet has already been fully defined, else a `ServletRegistration.Dynamic` object that can be used to further configure the servlet
    Throws:
      `IllegalStateException` - If the context has already been initialised
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addJspFile

    ServletRegistration.Dynamic addJspFile(String jspName, String jspFile)
    Add a JSP to the context.
    Parameters:
      `jspName` - The servlet name under which this JSP file should be registered
      `jspFile` - The path, relative to the web application root, for the JSP file to be used for this servlet
    Returns:
      a `ServletRegistration.Dynamic` object that can be used to further configure the servlet
    Since:
      Servlet 4.0

  - ### createServlet

    <T extends Servlet> T createServlet(Class<T> c) throws ServletException
    Create an Servlet instance using the given class. The instance is just created. No initialisation occurs.
    Type Parameters:
      `T` - The type for the given class
    Parameters:
      `c` - The the class for which an instance should be created
    Returns:
      The created Servlet instance.
    Throws:
      `ServletException` - If the servlet instance cannot be created.
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getServletRegistration

    ServletRegistration getServletRegistration(String servletName)
    Obtain the details of the named servlet.
    Parameters:
      `servletName` - The name of the Servlet of interest
    Returns:
      The registration details for the named Servlet or `null` if no Servlet has been registered with the given name
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getServletRegistrations

    Map<String, ? extends ServletRegistration> getServletRegistrations()
    Obtain a Map of servlet names to servlet registrations for all servlets registered with this context.
    Returns:
      A Map of servlet names to servlet registrations for all servlets registered with this context
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addFilter

    FilterRegistration.Dynamic addFilter(String filterName, String className)
    Add filter to context.
    Parameters:
      `filterName` - Name of filter to add
      `className` - Name of filter class
    Returns:
      `null` if the filter has already been fully defined, else a `FilterRegistration.Dynamic` object that can be used to further configure the filter
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalStateException` - If the context has already been initialised
    Since:
      Servlet 3.0

  - ### addFilter

    FilterRegistration.Dynamic addFilter(String filterName, Filter filter)
    Add filter to context.
    Parameters:
      `filterName` - Name of filter to add
      `filter` - Filter to add
    Returns:
      `null` if the filter has already been fully defined, else a `FilterRegistration.Dynamic` object that can be used to further configure the filter
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalStateException` - If the context has already been initialised
    Since:
      Servlet 3.0

  - ### addFilter

    FilterRegistration.Dynamic addFilter(String filterName, Class<? extends Filter> filterClass)
    Add filter to context.
    Parameters:
      `filterName` - Name of filter to add
      `filterClass` - Class of filter to add
    Returns:
      `null` if the filter has already been fully defined, else a `FilterRegistration.Dynamic` object that can be used to further configure the filter
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalStateException` - If the context has already been initialised
    Since:
      Servlet 3.0

  - ### createFilter

    <T extends Filter> T createFilter(Class<T> c) throws ServletException
    Create a Filter instance using the given class. The instance is just created. No initialisation occurs.
    Type Parameters:
      `T` - The type for the given class
    Parameters:
      `c` - The the class for which an instance should be created
    Returns:
      The created Filter instance.
    Throws:
      `ServletException` - If the Filter instance cannot be created
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getFilterRegistration

    FilterRegistration getFilterRegistration(String filterName)
    TODO SERVLET3 - Add comments
    Parameters:
      `filterName` - TODO
    Returns:
      TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getFilterRegistrations

    Map<String, ? extends FilterRegistration> getFilterRegistrations()
    Returns:
      TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0 TODO SERVLET3 - Add comments

  - ### getSessionCookieConfig

    SessionCookieConfig getSessionCookieConfig()
    Returns:
      TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0 TODO SERVLET3 - Add comments

  - ### setSessionTrackingModes

    void setSessionTrackingModes(Set<SessionTrackingMode> sessionTrackingModes)
    Configures the available session tracking modes for this web application.
    Parameters:
      `sessionTrackingModes` - The session tracking modes to use for this web application
    Throws:
      `IllegalArgumentException` - If sessionTrackingModes specifies `SessionTrackingMode.SSL` in combination with any other `SessionTrackingMode`
      `IllegalStateException` - If the context has already been initialised
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getDefaultSessionTrackingModes

    Set<SessionTrackingMode> getDefaultSessionTrackingModes()
    Obtains the default session tracking modes for this web application. By default `SessionTrackingMode.URL` is always supported, `SessionTrackingMode.COOKIE` is supported unless the `cookies` attribute has been set to `false` for the context and `SessionTrackingMode.SSL` is supported if at least one of the connectors used by this context has the attribute `secure` set to `true`.
    Returns:
      The set of default session tracking modes for this web application
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getEffectiveSessionTrackingModes

    Set<SessionTrackingMode> getEffectiveSessionTrackingModes()
    Obtains the currently enabled session tracking modes for this web application.
    Returns:
      The value supplied via `setSessionTrackingModes(Set)` if one was previously set, else return the defaults
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addListener

    void addListener(String className)
    TODO SERVLET3 - Add comments
    Parameters:
      `className` - TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addListener

    <T extends EventListener> void addListener(T t)
    TODO SERVLET3 - Add comments
    Type Parameters:
      `T` - TODO
    Parameters:
      `t` - TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### addListener

    void addListener(Class<? extends EventListener> listenerClass)
    TODO SERVLET3 - Add comments
    Parameters:
      `listenerClass` - TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### createListener

    <T extends EventListener> T createListener(Class<T> c) throws ServletException
    TODO SERVLET3 - Add comments
    Type Parameters:
      `T` - TODO
    Parameters:
      `c` - TODO
    Returns:
      TODO
    Throws:
      `ServletException` - TODO
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0

  - ### getJspConfigDescriptor

    JspConfigDescriptor getJspConfigDescriptor()
    Returns:
      TODO
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 3.0 TODO SERVLET3 - Add comments

  - ### getClassLoader

    ClassLoader getClassLoader()
    Get the web application class loader associated with this ServletContext.
    Returns:
      The associated web application class loader
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `SecurityException` - if access to the class loader is prevented by a SecurityManager
    Since:
      Servlet 3.0

  - ### declareRoles

    void declareRoles(String... roleNames)
    Add to the declared roles for this ServletContext.
    Parameters:
      `roleNames` - The roles to add
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalArgumentException` - If the list of roleNames is null or empty
      `IllegalStateException` - If the ServletContext has already been initialised
    Since:
      Servlet 3.0

  - ### getVirtualServerName

    String getVirtualServerName()
    Get the primary name of the virtual host on which this context is deployed. The name may or may not be a valid host name.
    Returns:
      The primary name of the virtual host on which this context is deployed
    Since:
      Servlet 3.1

  - ### getSessionTimeout

    int getSessionTimeout()
    Get the default session timeout.
    Returns:
      The current default session timeout in minutes
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 4.0

  - ### setSessionTimeout

    void setSessionTimeout(int sessionTimeout)
    Set the default session timeout. This method may only be called before the ServletContext is initialised.
    Parameters:
      `sessionTimeout` - The new default session timeout in minutes.
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalStateException` - If the ServletContext has already been initialised
    Since:
      Servlet 4.0

  - ### getRequestCharacterEncoding

    String getRequestCharacterEncoding()
    Get the default character encoding for reading request bodies.
    Returns:
      The character encoding name or `null` if no default has been specified
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 4.0

  - ### setRequestCharacterEncoding

    void setRequestCharacterEncoding(String encoding)
    Set the default character encoding to use for reading request bodies. Calling this method will over-ride any value set in the deployment descriptor.
    Parameters:
      `encoding` - The name of the character encoding to use
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalStateException` - If the ServletContext has already been initialised
    Since:
      Servlet 4.0

  - ### getResponseCharacterEncoding

    String getResponseCharacterEncoding()
    Get the default character encoding for writing response bodies.
    Returns:
      The character encoding name or `null` if no default has been specified
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
    Since:
      Servlet 4.0

  - ### setResponseCharacterEncoding

    void setResponseCharacterEncoding(String encoding)
    Set the default character encoding to use for writing response bodies. Calling this method will over-ride any value set in the deployment descriptor.
    Parameters:
      `encoding` - The name of the character encoding to use
    Throws:
      `UnsupportedOperationException` - If called from a `ServletContextListener.contextInitialized(ServletContextEvent)` method of a `ServletContextListener` that was not defined in a web.xml file, a web-fragment.xml file nor annotated with `WebListener`. For example, a `ServletContextListener` defined in a TLD would not be able to use this method.
      `IllegalStateException` - If the ServletContext has already been initialised
    Since:
      Servlet 4.0