Java-ServletContext

//定义了一系列servlet用来与servlet 容器交流的方法
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
* @see 		RequestDispatcher
*
*/
//返回一个ServletContext对象，它在服务器上与特定的URL相联系
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
*
*/
//返回 servlet容器支持的Servlet API主版本
public int getMajorVersion();
/**
* Returns the minor version of the Servlet API that this
* servlet container supports. All implementations that comply
*/
//返回servlet容器支持的Servlet API的次版本
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
*/
//返回特定文件的mime类型
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
*/
//返回资源路径，一个集合
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.
* @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
*
*/
//返回某个path的URL
public URL getResource(String path) throws MalformedURLException;

/**
* Returns the resource located at the named path as
* an <code>InputStream</code> object.
* <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
*/
//将路径下的资源以inputstream的方式返回
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
*
*/
//返回一个请求分发器对象，作为一个路径资源的包装
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}.
* @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
*
*/
//返回一个请求分发器作为一个实名Servlet的包装
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
*/
//写日志
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
*/
//获得servlet当前运行的servlet容器的信息
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 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
* <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>.
* @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();
}