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.     * @returnthe <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 paththe 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);    /**     *     * @deprecatedAs 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;                  /**     *     * @deprecatedAs 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();                        /**     * @deprecatedAs 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);    /**     * @deprecatedAs 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.     * @paramnamea <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 namea <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();}