ServletContext Class

Provides a mechanism to store application data across servlets. The ServletContext is initialized when the web server is initialized. There is only one context per Java Virtual Machine.

This class is a partial implementation of the javax.servlet.ServletContext interface defined in Version 2.5 of the Java Servlet API.

Constructors

public ServletContext( javax.servlet.ServletContext servletContext )

Methods

getAttribute( String name ) returns Object
Returns the servlet container attribute with the given name, or null if there is no attribute by that name.
getAttributeNames( ) returns java.util.Enumeration
Returns an Enumeration containing the attribute names available within this servlet context. Use the getAttribute() method with an attribute name to get the value of an attribute.
getContext( String uripath ) returns javax.servlet.ServletContext
Returns a ServletContext object that corresponds to a specified URL on the server, or null if either none exists or the container wishes to restrict this access.

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.

getContextPath( ) returns String
getInitParameter( String name ) returns String
Returns the value of the named context-wide initialization parameter, or null if the parameter does not exist. Initialization parameters are used to store configuration information for an entire "web application". For example, it can provide a webmaster's email address or the name of a system that holds critical data.
getInitParameterNames( ) returns java.util.Enumeration
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.
getMajorVersion( ) returns int
Returns the major version of the Java Servlet API that this servlet container supports.
getMimeType( String file ) returns String
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".
getMinorVersion( ) returns int
Returns the minor version of the Servlet API that this servlet container supports.
getNamedDispatcher( String name ) returns Object
Returns a RequestDispatcher that acts as a wrapper for the named servlet. Returns a null if the ServletContext cannot return a RequestDispatcher for any reason. Servlets are given names programatically or via a web application deployment descriptor. A servlet instance can determine its name using ServletConfig.getServletName().
nameA String specifying the name of a servlet to wrap.
getRealPath( String path ) returns String
Returns a String containing the real path for a given virtual path. For example, the path "/index.html" found in:
http://localhost:8080/WebApplication/index.html
might represent a physical file found in:
D:\WebApps\WebApplication\index.html
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 .
pathA String specifying a virtual path (e.g. "/index.html").
getRequestDispatcher( String path ) returns Object
Returns a RequestDispatcher that acts as a wrapper for a resource located at the given path. A RequestDispatcher 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.

getResource( String path ) returns java.net.URL
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.

patha String specifying the path to the resource
getResourceAsStream( String path ) returns java.io.InputStream
Returns the resource located at the named path as an InputStream.

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.

getResourcePaths( String path ) returns java.util.Set
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 '/'. Consider, for example, 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
    
context.getResourcePaths("/") would return "/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"
context.getResourcePaths("/catalog/") would return "/catalog/index.html", "/catalog/products.html", "/catalog/offers/".
pathThe partial path used to match the resources, which must start with a "/".
getServerInfo( ) returns String
Returns the name and version of the servlet container on which the servlet is running. The form of the returned string is servername/versionnumber. Example:
JavaServer Web Dev Kit/1.0
The servlet container may return other optional information after the primary string, in parentheses. Example:
JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)
getServletContextName( ) returns String
Returns the name of the web application or null if no name has been declared in the deployment descriptor.
log( String msg ) returns void
Writes the specified message to a servlet log file.
log( String message, Throwable throwable ) returns void
Writes an explanatory message and a stack trace for a given Throwable exception to the servlet log file.
removeAttribute( String name ) returns void
Removes the attribute with the given name from the servlet context. If listeners are configured on the ServletContext the container notifies them accordingly.
setAttribute( String name, Object value ) returns void
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 a null value is passed, the effect is the same as calling removeAttribute(). If listeners are configured on the ServletContext the container notifies them accordingly.