GenericServlet.java
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上传日期:2022-07-20
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数据库编程
开发平台:
Java
- /*
- * The Apache Software License, Version 1.1
- *
- * Copyright (c) 1999 The Apache Software Foundation. All rights
- * reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * 3. The end-user documentation included with the redistribution, if
- * any, must include the following acknowlegement:
- * "This product includes software developed by the
- * Apache Software Foundation (http://www.apache.org/)."
- * Alternately, this acknowlegement may appear in the software itself,
- * if and wherever such third-party acknowlegements normally appear.
- *
- * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
- * Foundation" must not be used to endorse or promote products derived
- * from this software without prior written permission. For written
- * permission, please contact apache@apache.org.
- *
- * 5. Products derived from this software may not be called "Apache"
- * nor may "Apache" appear in their names without prior written
- * permission of the Apache Group.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
- * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- * ====================================================================
- *
- * This software consists of voluntary contributions made by many
- * individuals on behalf of the Apache Software Foundation. For more
- * information on the Apache Software Foundation, please see
- * <http://www.apache.org/>.
- *
- * ====================================================================
- *
- * This source code implements specifications defined by the Java
- * Community Process. In order to remain compliant with the specification
- * DO NOT add / change / or delete method signatures!
- */
- package javax.servlet;
- import java.io.IOException;
- import java.util.Enumeration;
- /**
- *
- * Defines a generic, protocol-independent
- * servlet. To write an HTTP servlet for use on the
- * Web, extend {@link javax.servlet.http.HttpServlet} instead.
- *
- * <p><code>GenericServlet</code> implements the <code>Servlet</code>
- * and <code>ServletConfig</code> interfaces. <code>GenericServlet</code>
- * may be directly extended by a servlet, although it's more common to extend
- * a protocol-specific subclass such as <code>HttpServlet</code>.
- *
- * <p><code>GenericServlet</code> makes writing servlets
- * easier. It provides simple versions of the lifecycle methods
- * <code>init</code> and <code>destroy</code> and of the methods
- * in the <code>ServletConfig</code> interface. <code>GenericServlet</code>
- * also implements the <code>log</code> method, declared in the
- * <code>ServletContext</code> interface.
- *
- * <p>To write a generic servlet, you need only
- * override the abstract <code>service</code> method.
- *
- *
- * @author Various
- * @version $Version$
- *
- *
- *
- */
- public abstract class GenericServlet
- implements Servlet, ServletConfig, java.io.Serializable
- {
- private transient ServletConfig config;
- /**
- *
- * Does nothing. All of the servlet initialization
- * is done by one of the <code>init</code> methods.
- *
- */
- public GenericServlet() { }
- /**
- * Called by the servlet container to indicate to a servlet that the
- * servlet is being taken out of service. See {@link Servlet#destroy}.
- *
- *
- */
- public void destroy() {
- log("destroy");
- }
- /**
- * Returns a <code>String</code> containing the value of the named
- * initialization parameter, or <code>null</code> if the parameter does
- * not exist. See {@link ServletConfig#getInitParameter}.
- *
- * <p>This method is supplied for convenience. It gets the
- * value of the named parameter from the servlet's
- * <code>ServletConfig</code> object.
- *
- * @param name a <code>String</code> specifying the name
- * of the initialization parameter
- *
- * @return String a <code>String</code> containing the value
- * of the initalization parameter
- *
- */
- public String getInitParameter(String name) {
- return getServletConfig().getInitParameter(name);
- }
- /**
- * Returns the names of the servlet's initialization parameters
- * as an <code>Enumeration</code> of <code>String</code> objects,
- * or an empty <code>Enumeration</code> if the servlet has no
- * initialization parameters. See {@link
- * ServletConfig#getInitParameterNames}.
- *
- * <p>This method is supplied for convenience. It gets the
- * parameter names from the servlet's <code>ServletConfig</code> object.
- *
- *
- * @return Enumeration an enumeration of <code>String</code>
- * objects containing the names of
- * the servlet's initialization parameters
- *
- */
- public Enumeration getInitParameterNames() {
- return getServletConfig().getInitParameterNames();
- }
- /**
- * Returns this servlet's {@link ServletConfig} object.
- *
- * @return ServletConfig the <code>ServletConfig</code> object
- * that initialized this servlet
- *
- */
- public ServletConfig getServletConfig() {
- return config;
- }
- /**
- * Returns a reference to the {@link ServletContext} in which this servlet
- * is running. See {@link ServletConfig#getServletContext}.
- *
- * <p>This method is supplied for convenience. It gets the
- * context from the servlet's <code>ServletConfig</code> object.
- *
- *
- * @return ServletContext the <code>ServletContext</code> object
- * passed to this servlet by the <code>init</code>
- * method
- *
- */
- public ServletContext getServletContext() {
- return getServletConfig().getServletContext();
- }
- /**
- * Returns information about the servlet, such as
- * author, version, and copyright.
- * By default, this method returns an empty string. Override this method
- * to have it return a meaningful value. See {@link
- * Servlet#getServletInfo}.
- *
- *
- * @return String information about this servlet, by default an
- * empty string
- *
- */
- public String getServletInfo() {
- return "";
- }
- /**
- *
- * Called by the servlet container to indicate to a servlet that the
- * servlet is being placed into service. See {@link Servlet#init}.
- *
- * <p>This implementation stores the {@link ServletConfig}
- * object it receives from the servlet container for alter use.
- * When overriding this form of the method, call
- * <code>super.init(config)</code>.
- *
- * @param config the <code>ServletConfig</code> object
- * that contains configutation
- * information for this servlet
- *
- * @exception ServletException if an exception occurs that
- * interrupts the servlet's normal
- * operation
- *
- *
- * @see UnavailableException
- *
- */
- public void init(ServletConfig config) throws ServletException {
- this.config = config;
- log("init");
- this.init();
- }
- /**
- *
- * A convenience method which can be overridden so that there's no need
- * to call <code>super.init(config)</code>.
- *
- * <p>Instead of overriding {@link #init(ServletConfig)}, simply override
- * this method and it will be called by
- * <code>GenericServlet.init(ServletConfig config)</code>.
- * The <code>ServletConfig</code> object can still be retrieved via {@link
- * #getServletConfig}.
- *
- * @exception ServletException if an exception occurs that
- * interrupts the servlet's
- * normal operation
- *
- */
- public void init() throws ServletException {
- }
- /**
- *
- * Writes the specified message to a servlet log file, prepended by the
- * servlet's name. See {@link ServletContext#log(String)}.
- *
- * @param msg a <code>String</code> specifying
- * the message to be written to the log file
- *
- */
- public void log(String msg) {
- getServletContext().log(getServletName() + ": "+ msg);
- }
- /**
- * Writes an explanatory message and a stack trace
- * for a given <code>Throwable</code> exception
- * to the servlet log file, prepended by the servlet's name.
- * See {@link ServletContext#log(String, Throwable)}.
- *
- *
- * @param message a <code>String</code> that describes
- * the error or exception
- *
- * @param t the <code>java.lang.Throwable</code> error
- * or exception
- *
- *
- */
- public void log(String message, Throwable t) {
- getServletContext().log(getServletName() + ": " + message, t);
- }
- /**
- * Called by the servlet container to allow the servlet to respond to
- * a request. See {@link Servlet#service}.
- *
- * <p>This method is declared abstract so subclasses, such as
- * <code>HttpServlet</code>, must override it.
- *
- *
- *
- * @param req the <code>ServletRequest</code> object
- * that contains the client's request
- *
- * @param res the <code>ServletResponse</code> object
- * that will contain the servlet's response
- *
- * @exception ServletException if an exception occurs that
- * interferes with the servlet's
- * normal operation occurred
- *
- * @exception IOException if an input or output
- * exception occurs
- *
- */
- public abstract void service(ServletRequest req, ServletResponse res)
- throws ServletException, IOException;
- /**
- * Returns the name of this servlet instance.
- * See {@link ServletConfig#getServletName}.
- *
- * @return the name of this servlet instance
- *
- *
- *
- */
- public String getServletName() {
- return config.getServletName();
- }
- }