servlet从入门到精通

package cn.servlet.wyx;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class servletTest implements Servlet {
    /**
     * 动态网站之所以被称为动态网站最主要的就是因为servlet，而servlet需要web.xml来配置，通过解析这个文件
     * 完成反射；
     * servlet特性：
     * 每个servlet都是单例设计，并且不同步；
     * 而访问servlet都是多线程操作，所以一定要注意线程安全问题，会在之后文章中做详解；
     * */
    @Override
    public void destroy() {
        System.out.println("生命周期方法，tamcat关闭时调用，我们一般不会修改本方法");
    }

    @Override
    public ServletConfig getServletConfig() {

        return null;
    }

    @Override
    public String getServletInfo() {

        return "这是一个快乐的servlet";
    }

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        System.out.println("生命周期方法，tamcat初始化方法，注意参数servletConfig");
    }

    @Override
    public void service(ServletRequest arg0, ServletResponse arg1)
            throws ServletException, IOException {
        System.out.println("生命周期方法，处理请求，需要我们自己写");
    }

}

package cn.gendericServlet.wyx;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class ServletToGendericServlet implements Servlet {
    ServletConfig servletConfig;
    /*
     * getServletContext这是一个模拟GendericServlet抽象类的一个方法；
     * */
    public ServletContext getServletContext(){
        return this.servletConfig.getServletContext();
    }
    public String getInitParameter(String name){
        return servletConfig.getInitParameter(name);
    }
    @Override
    public void destroy() {
    }

    @Override
    public ServletConfig getServletConfig() {

        return servletConfig;
    }

    @Override
    public String getServletInfo() {

        return null;
    }

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        this.servletConfig=servletConfig;
        init();
    }

    public void init() {
        //put your code here;
    }

    @Override
    public void service(ServletRequest arg0, ServletResponse arg1)
            throws ServletException, IOException {
    }

}

package cn.gendericServlet.wyx;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class GendericServletTest extends GenericServlet {

    @Override
    public void service(ServletRequest arg0, ServletResponse arg1)
            throws ServletException, IOException {
    }

    /**
     * Constructor of the object.
     */
    public GendericServletTest() {
        super();
    }

    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }

    /**
     * The doDelete method of the servlet. <br>
     *
     * This method is called when a HTTP delete request is received.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doDelete(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {

        // Put your code here
    }

    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the GET method");
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the POST method");
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    /**
     * The doPut method of the servlet. <br>
     *
     * This method is called when a HTTP put request is received.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPut(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // Put your code here
    }

    /**
     * Returns information about the servlet, such as 
     * author, version, and copyright. 
     *
     * @return String information about this servlet
     */
    public String getServletInfo() {
        return "This is my default servlet created by Eclipse";
    }

    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }

}

package cn.httpServlet.wyx;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HttpServletTest extends HttpServlet {
    /**
     * 
     * HttpServlet抽象类原理：
     * {
     *         service(ServletRequest request,ServletResponse response){
     *             HttpServletRequest hreq = request;
     *             HttpServletResponse hres = response;
     *             service(hreq, hres);
     *         }
     *         service(HttpServletRequest request, HttpServletResponse response){
     *             通过request获取到传输方法（get/post/put）
     *             通过判断调用doGet(HttpServletRequest request, HttpServletResponse response)或
     *             doPost(HttpServletRequest request, HttpServletResponse response);
     *             doPut(HttpServletRequest request, HttpServletResponse response);
     *             
     *         }
     *         doGet(HttpServletRequest request, HttpServletResponse response){
     *             我们自己需要重写的方法，如果不重写，会报405错误；doPost()doPut()方法同doGet（）
     *         }
     * 
     * }
     * */

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the GET method");
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
　　　　　　//获取请求参数
        String username = (String) request.getAttribute("username");
        String password = (String)request.getAttribute("password");
        System.out.println(username+":"+password);
    }

}

package cn.ServletContext.wyx;

import java.io.IOException;
import java.io.InputStream;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class ServletContextTest extends HttpServlet {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    /*实现网站访问量统计*/
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            Integer times = (Integer)getServletContext().getAttribute("times");
            if(times!=null){
                times++;
            }else{
                times=1;
            }
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().print("<h3>访问量统计:"+times+"次</h3>");
            getServletContext().setAttribute("times", times);
    }

    /**
     * 获取所有servlet初始化参数--context-param:
     * servlet常用流介绍:
     * */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            String value = getServletContext().getInitParameter("context-name");
            System.out.println(value);
        
        //可以获取到项目的真实路径,有盘符的路径
            String path = getServletContext().getRealPath("/index.jsp");
            System.out.println(path);
            //获取所有资源路径
            Set<String> paths = getServletContext().getResourcePaths("/任意路径");
            System.out.println(paths);
            
            InputStream in = getServletContext().getResourceAsStream("在webapps的项目路径下index.jsp");
            InputStream inp = this.getClass().getClassLoader().getResourceAsStream("在classse目录下");
            InputStream ins = getClass().getResourceAsStream("在.class路径下");
        　　//getClass().getResourceAsStream（“”）加上/则在classse目录下，不加就在.class目录下（备注）
    }

}

 web.xml文件配置（重要，能够达到手写标准）

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <display-name></display-name>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>GendericServletTest</servlet-name>
    <servlet-class>cn.gendericServlet.wyx.GendericServletTest</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>HttpServletTest</servlet-name>
    <servlet-class>cn.httpServlet.wyx.HttpServletTest</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>ServletContextTest</servlet-name>
    <servlet-class>cn.ServletContext.wyx.ServletContextTest</servlet-class>
  </servlet>



  <servlet-mapping>
    <servlet-name>GendericServletTest</servlet-name>
    <url-pattern>/GendericServletTest</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>HttpServletTest</servlet-name>
    <url-pattern>/HttpServletTest</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ServletContextTest</servlet-name>
    <url-pattern>/ServletContextTest</url-pattern>
  </servlet-mapping>    
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <context-param>
      <param-name>context-name</param-name>
      <param-value>context-value</param-value>
  </context-param>
</web-app>