public interface ServletContext {
//context path是请求URI的一部分，通常用于选择请求的context.这个路径是以"/"开头的
//For servlets in the default (root) context, this method returns "".
public String getContextPath();
/**
* 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);
//返回容器支持的servlet API 的主版本号
public int getMajorVersion();
public int getMinorVersion();
//返回指定文件的MIME类型，如果不清楚，就返回null
//这个MIME类型是由servlet容器的配置所决定的，也可以被web部署描述指定
//通常MIME类型是text/html和image/gif
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 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>.
*
* <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();
}
