javax.servlet.ServletContext Maven / Gradle / Ivy
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*
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*
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
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* License along with this software; if not, write to the Free
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*/
package javax.servlet;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Set;
/**
* 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
* {@link ServletConfig} object, which the Web server provides the servlet when
* the servlet is initialized.
*
* @author Various
* @see Servlet#getServletConfig
* @see ServletConfig#getServletContext
*/
public interface ServletContext
{
/**
* Returns the context path of the web application.
*
* The context path is the portion of the request URI that is used to select
* the context of the request. The context path always comes first in a
* request URI. The path starts with a "/" character but does not end with a
* "/" character. For servlets in the default (root) context, this method
* returns "".
*
* It is possible that a servlet container may match a context by more than
* one context path. In such cases the
* {@link javax.servlet.http.HttpServletRequest#getContextPath()} will return
* the actual context path used by the request and it may differ from the
* path returned by this method. The context path returned by this method
* should be considered as the prime or preferred context path of the
* application.
*
* @return The context path of the web application, or "" for the default
* (root) context
* @see javax.servlet.http.HttpServletRequest#getContextPath()
* @since Servlet 2.5
*/
public String getContextPath();
/**
* 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 2.5 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 2.5 must have this
* method return the integer 5.
*
* @return 5
*/
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.
*/
@Deprecated
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.
*/
@Deprecated
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.
*/
@Deprecated
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 corresponding 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();
}