/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
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.
*
* <p>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 <code>/catalog</code>
* and possibly installed via a <code>.war</code> file.)
*
* <p>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.
*
* <p>The <code>ServletContext</code> 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 a <code>ServletContext</code> object that
* corresponds to a specified URL on the server.
*
* <p>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.
*
* <p>In a security conscious environment, the servlet container may
* return <code>null</code> for a given URL.
*
* @param uripath a <code>String</code> specifying the context path of
* another web application in the container.
* @return the <code>ServletContext</code> 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);
public String getContextPath();
/**
* 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 2.5 must have this method
* return the integer 5.
*
* @return 5
*
*/
public int getMinorVersion();
/**
* Returns the MIME type of the specified file, or <code>null</code> 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 <code>"text/html"</code> and <code>"image/gif"</code>.
*
*
* @param file a <code>String</code> specifying the name
* of a file
*
* @return a <code>String</code> 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<br><br>
* /welcome.html<br>
* /catalog/index.html<br>
* /catalog/products.html<br>
* /catalog/offers/books.html<br>
* /catalog/offers/music.html<br>
* /customer/login.jsp<br>
* /WEB-INF/web.xml<br>
* /WEB-INF/classes/com.acme.OrderServlet.class,<br><br>
*
* getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}<br>
* getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.<br>
*@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.
*
* <p>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 <code>.war</code> file.
*
* <p>The servlet container must implement the URL handlers
* and <code>URLConnection</code> objects that are necessary
* to access the resource.
*
* <p>This method returns <code>null</code>
* if no resource is mapped to the pathname.
*
* <p>Some containers may allow writing to the URL returned by
* this method using the methods of the URL class.
*
* <p>The resource content is returned directly, so be aware that
* requesting a <code>.jsp</code> page returns the JSP source code.
* Use a <code>RequestDispatcher</code> instead to include results of
* an execution.
*
* <p>This method has a different purpose than
* <code>java.lang.Class.getResource</code>,
* which looks up resources based on a class loader. This
* method does not use class loaders.
*
* @param path a <code>String</code> specifying
* the path to the resource
*
* @return the resource located at the named path,
* or <code>null</code> 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 <code>InputStream</code> object.
*
* <p>The data in the <code>InputStream</code> can be
* of any type or length. The path must be specified according
* to the rules given in <code>getResource</code>.
* This method returns <code>null</code> if no resource exists at
* the specified path.
*
* <p>Meta-information such as content length and content type
* that is available via <code>getResource</code>
* method is lost when using this method.
*
* <p>The servlet container must implement the URL handlers
* and <code>URLConnection</code> objects necessary to access
* the resource.
*
* <p>This method is different from
* <code>java.lang.Class.getResourceAsStream</code>,
* 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 <code>String</code> specifying the path
* to the resource
*
* @return the <code>InputStream</code> returned to the
* servlet, or <code>null</code> 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 <code>RequestDispatcher</code> 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.
*
* <p>The pathname must begin with a "/" and is interpreted as relative
* to the current context root. Use <code>getContext</code> to obtain
* a <code>RequestDispatcher</code> for resources in foreign contexts.
* This method returns <code>null</code> if the <code>ServletContext</code>
* cannot return a <code>RequestDispatcher</code>.
*
* @param path a <code>String</code> specifying the pathname
* to the resource
*
* @return a <code>RequestDispatcher</code> object
* that acts as a wrapper for the resource
* at the specified path, or <code>null</code> if
* the <code>ServletContext</code> cannot return
* a <code>RequestDispatcher</code>
*
* @see RequestDispatcher
* @see ServletContext#getContext
*
*/
public RequestDispatcher getRequestDispatcher(String path);
/**
* Returns a {@link RequestDispatcher} object that acts
* as a wrapper for the named servlet.
*
* <p>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}.
*
* <p>This method returns <code>null</code> if the
* <code>ServletContext</code>
* cannot return a <code>RequestDispatcher</code> for any reason.
*
* @param name a <code>String</code> specifying the name
* of a servlet to wrap
*
* @return a <code>RequestDispatcher</code> object
* that acts as a wrapper for the named servlet,
* or <code>null</code> if the <code>ServletContext</code>
* cannot return a <code>RequestDispatcher</code>
*
* @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.
*
* <p>This method was originally defined to retrieve a servlet
* from a <code>ServletContext</code>. In this version, this method
* always returns <code>null</code> and remains only to preserve
* binary compatibility. This method will be permanently removed
* in a future version of the Java Servlet API.
*
* <p>In lieu of this method, servlets can share information using the
* <code>ServletContext</code> 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.
*
* <p>This method was originally defined to return an <code>Enumeration</code>
* 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.
*
* <p>This method was originally defined to return an
* <code>Enumeration</code>
* of all the servlet names known to this context. In this version,
* this method always returns an empty <code>Enumeration</code> 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 <code>String</code> 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.
*
* <p>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 <code>Throwable</code> 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 <code>String</code> that
* describes the error or exception
*
* @param throwable the <code>Throwable</code> error
* or exception
*
*/
public void log(String message, Throwable throwable);
/**
* Returns a <code>String</code> 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..
*
* <p>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 <code>null</code>
* 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 <code>.war</code> archive).
*
*
* @param path a <code>String</code> specifying a virtual path
*
*
* @return a <code>String</code> 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.
*
* <p>The form of the returned string is
* <i>servername</i>/<i>versionnumber</i>.
* For example, the JavaServer Web Development Kit may return the string
* <code>JavaServer Web Dev Kit/1.0</code>.
*
* <p>The servlet container may return other optional information
* after the primary string in parentheses, for example,
* <code>JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)</code>.
*
*
* @return a <code>String</code> containing at least the
* servlet container name and version number
*
*/
public String getServerInfo();
/**
* Returns a <code>String</code> containing the value of the named
* context-wide initialization parameter, or <code>null</code> if the
* parameter does not exist.
*
* <p>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 <code>String</code> containing the name of the parameter
* whose value is requested
* @return a <code>String</code> containing the value of the initialization
* parameter
* @see ServletConfig#getInitParameter
*/
public String getInitParameter(String name);
/**
* Returns the names of the context's initialization parameters as an
* <code>Enumeration</code> of <code>String</code> objects, or an
* empty <code>Enumeration</code> if the context has no initialization
* parameters.
*
* @return an <code>Enumeration</code> of <code>String</code>
* 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 <code>null</code> 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
* <code>getAttributeNames</code>.
*
* <p>The attribute is returned as a <code>java.lang.Object</code>
* or some subclass.
* Attribute names should follow the same convention as package
* names. The Java Servlet API specification reserves names
* matching <code>java.*</code>, <code>javax.*</code>,
* and <code>sun.*</code>.
*
*
* @param name a <code>String</code> specifying the name
* of the attribute
*
* @return an <code>Object</code> containing the value
* of the attribute, or <code>null</code>
* if no attribute exists matching the given
* name
*
* @see ServletContext#getAttributeNames
*
*/
public Object getAttribute(String name);
/**
* Returns an <code>Enumeration</code> 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 <code>Enumeration</code> 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.
* <p>If listeners are configured on the <code>ServletContext</code> the
* container notifies them accordingly.
* <p>
* If a null value is passed, the effect is the same as calling
* <code>removeAttribute()</code>.
*
* <p>Attribute names should follow the same convention as package
* names. The Java Servlet API specification reserves names
* matching <code>java.*</code>, <code>javax.*</code>, and
* <code>sun.*</code>.
*
*
* @param name a <code>String</code> specifying the name
* of the attribute
*
* @param object an <code>Object</code> 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 <code>null</code>.
* <p>If listeners are configured on the <code>ServletContext</code> the
* container notifies them accordingly.
*
*
* @param name a <code>String</code> 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();
}