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 {@link ServletConfig} object, which the Web server provides the
* servlet when the servlet is initialized.
*
* @see Servlet#getServletConfig
* @see ServletConfig#getServletContext
*
* @version $Rev$ $Date$
*/
public interface ServletContext {
/**
* 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 {@link 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.
*
* @param uripath a String specifying the context path of
* another web application in the container.
* @return the ServletContext object that
* corresponds to the named URL, or null if either none exists or the
* container wishes to restrict this access.
*
* @see RequestDispatcher
*/
public ServletContext getContext(String uripath);
/**
* Returns the major version of the Java Servlet API that this
* servlet container supports. All implementations that comply
* with Version 2.4 must have this method
* return the integer 2.
*
* @return 2
*/
public int getMajorVersion();
/**
* Returns the minor version of the Servlet API that this
* servlet container supports. All implementations that comply
* with Version 2.4 must have this method
* return the integer 4.
*
* @return 4
*/
public int getMinorVersion();
/**
* 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".
*
* @param file a String specifying the name
* of a file
*
* @return a String specifying the file's MIME type
*/
public String getMimeType(String file);
/**
* 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/"}.
*
* @param path the partial path used to match the resources,
* which must start with a /
* @return 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
*/
public Set getResourcePaths(String path);
/**
* 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.
*
* @param path a String specifying the path to the resource
*
* @return the resource located at the named path, or null
* if there is no resource at that path
*
* @exception MalformedURLException if the pathname is not given in
* the correct form
*/
public URL getResource(String path) throws MalformedURLException;
/**
* 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.
*
* @param path a String specifying the path
* to the resource
*
* @return the InputStream returned to the
* servlet, or null if no resource exists at the
* specified path
*/
public InputStream getResourceAsStream(String path);
/**
* Returns a {@link 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.
*
* @param path a String specifying the pathname
* to the resource
*
* @return 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 RequestDispatcher
* @see ServletContext#getContext
*/
public RequestDispatcher getRequestDispatcher(String path);
/**
* Returns a {@link 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 * {@link ServletConfig#getServletName}. * *
This method returns null if the
* ServletContext
* cannot return a RequestDispatcher for any reason.
*
* @param name a String specifying the name
* of a servlet to wrap
*
* @return a RequestDispatcher object
* that acts as a wrapper for the named servlet,
* or null if the ServletContext
* cannot return a RequestDispatcher
*
* @see RequestDispatcher
* @see ServletContext#getContext
* @see ServletConfig#getServletName
*/
public RequestDispatcher getNamedDispatcher(String name);
/**
* @deprecated As of Java Servlet API 2.1, with no direct replacement.
*
*
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.
*/
public Servlet getServlet(String name) throws ServletException;
/**
* @deprecated As of Java Servlet API 2.0, with no replacement.
*
*
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.
*/
public Enumeration getServlets();
/**
* @deprecated As of Java Servlet API 2.1, with no replacement.
*
*
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.
*/
public Enumeration getServletNames();
/**
* 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.
*
* @param msg a String specifying the
* message to be written to the log file
*/
public void log(String msg);
/**
* @deprecated As of Java Servlet API 2.1, use
* {@link #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.
*/
public void log(Exception exception, String msg);
/**
* 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.
*
* @param message a String that
* describes the error or exception
*
* @param throwable the Throwable error
* or exception
*/
public void log(String message, Throwable throwable);
/**
* 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).
*
* @param path a String specifying a virtual path
*
* @return a String specifying the real path,
* or null if the translation cannot be performed
*/
public String getRealPath(String path);
/**
* 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).
*
* @return a String containing at least the
* servlet container name and version number
*/
public String getServerInfo();
/**
* 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
* webmaster's email address or the name of a system that holds
* critical data.
*
* @param name a String containing the name of the
* parameter whose value is requested
*
* @return a String containing at least the
* servlet container name and version number
*
* @see ServletConfig#getInitParameter
*/
public String getInitParameter(String name);
/**
* 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.
*
* @return an Enumeration of String
* objects containing the names of the context's initialization parameters
*
* @see ServletConfig#getInitParameter
*/
public Enumeration getInitParameterNames();
/**
* 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.*.
*
* @param name a String specifying the name
* of the attribute
*
* @return an Object containing the value
* of the attribute, or null if no attribute
* exists matching the given name
*
* @see ServletContext#getAttributeNames
*/
public Object getAttribute(String name);
/**
* Returns an Enumeration containing the
* attribute names available
* within this servlet context. Use the
* {@link #getAttribute} method with an attribute name
* to get the value of an attribute.
*
* @return an Enumeration of attribute names
*
* @see #getAttribute
*/
public Enumeration getAttributeNames();
/**
* 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.*.
*
* @param name a String specifying the name
* of the attribute
*
* @param object an Object representing the
* attribute to be bound
*/
public void setAttribute(String name, Object object);
/**
* Removes the attribute with the given name from
* the servlet context. After removal, subsequent calls to
* {@link #getAttribute} to retrieve the attribute's value
* will return null.
*
*
If listeners are configured on the ServletContext the
* container notifies them accordingly.
*
* @param name a String specifying the name
* of the attribute to be removed
*/
public void removeAttribute(String name);
/**
* Returns the name of this web application correponding to this ServletContext as specified in the deployment
* descriptor for this web application by the display-name element.
*
* @return The name of the web application or null if no name has been declared in the deployment descriptor.
* @since Servlet 2.3
*/
public String getServletContextName();
}