Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之12.Servlet基础(2)-阿里云开发者社区

–提交表单的方法
• get
• post
–Servlet 生命周期
–使用Servlet 输出HTML页面
–获得Servlet初始化参数
–页面导航
• 请求重定向
–response.sendRedirect(“url”);
• 请求转发
–request.getRequestDispatcher(“url”).forward(request,response);
• 请求包含
–request.getRequestDispatcher(“url”).include(request,response);

############Michael分割线################

全局参数对全局生效，我们来测试一下

ServletBasic2.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

public class ServletBasic2 extends HttpServlet {

         /**
         * Constructor of the object.
         */
         public ServletBasic2() {
                 super();
        }

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

        /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */
        public void init() throws ServletException {
                Enumeration enu = this.getServletContext().getInitParameterNames();
                while(enu.hasMoreElements()){
                        String name = (String) enu.nextElement();
                        String value = this.getServletContext().getInitParameter(name);
                        System.out.println(name+":"+value);
                }
        }

}

测试一下

–局部参数
• web.xml 配置

• 获得

web.xml

<? xml version ="1.0" encoding ="UTF-8" ?>
< web-app version ="2.4"
         xmlns ="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
         < context-param >
                 < param-name >driver </ param-name >
                 < param-value >com.mysql.jdbc.Driver </ param-value >
         </ context-param >
         < context-param >
                 < param-name >url </ param-name >
                 < param-value >jdbc:mysql://localhost:3306/jdbc_db </ param-value >
         </ context-param >
     < servlet >
         < servlet-name >ServletBasic </ servlet-name >
         < servlet-class >com.michael.servlet.ServletBasic </ servlet-class >
         < init-param >
                 < param-name >username </ param-name >
                 < param-value >michael </ param-value >
         </ init-param >
         < init-param >
                 < param-name >password </ param-name >
                 < param-value >111222 </ param-value >
         </ init-param >
     </ servlet >
     < servlet >
         < servlet-name >ServletBasic2 </ servlet-name >
         < servlet-class >com.michael.servlet.ServletBasic2 </ servlet-class >
     </ servlet >

     < servlet-mapping >
         < servlet-name >ServletBasic </ servlet-name >
         < url-pattern >/servlet/ServletBasic </ url-pattern >
     </ servlet-mapping >
     < servlet-mapping >
         < servlet-name >ServletBasic2 </ servlet-name >
         < url-pattern >/servlet/ServletBasic2 </ url-pattern >
     </ servlet-mapping >

</ web-app >

ServletBasic.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

public class ServletBasic extends HttpServlet {

         /**
         * Constructor of the object.
         */
         public ServletBasic() {
                 super();
                System.out.println( "-----ServletBasic-----");
        }

         /**
         * Destruction of the servlet. <br>
         */
         public void destroy() {
                 super.destroy();
                System.out.println( "-----destroy-----");
        }

         /**
         * 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 {
                System.out.println( "-----doGet-----");

                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 {
                System.out.println("-----doPost-----");
                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();
        }

        /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */
        public void init() throws ServletException {
                /*
                //第一种方法
                String driver = this.getServletContext().getInitParameter("driver");
                String url = this.getServletContext().getInitParameter("url");
                System.out.println(driver);
                System.out.println(url);
                //第二种方法
                Enumeration enu = this.getServletContext().getInitParameterNames();
                while(enu.hasMoreElements()){
                        String name = (String) enu.nextElement();
                        String value = this.getServletContext().getInitParameter(name);
                        System.out.println(name+":"+value);
                }
                */
                String username = this.getInitParameter("username");
                String password = this.getInitParameter("password");
                System.out.println(username);
                System.out.println(password);
                System.out.println("-----init-----");
        }

        @Override
        protected void service(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
                // TODO Auto-generated method stub
                System.out.println("-----service-----");
        }
}

ServletBasic2.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

public class ServletBasic2 extends HttpServlet {

         /**
         * Constructor of the object.
         */
         public ServletBasic2() {
                 super();
        }

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

        /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */
        public void init() throws ServletException {
                /*
                Enumeration enu = this.getServletContext().getInitParameterNames();
                while(enu.hasMoreElements()){
                        String name = (String) enu.nextElement();
                        String value = this.getServletContext().getInitParameter(name);
                        System.out.println(name+":"+value);
                }
                */
                String username = this.getInitParameter("username");
                String password = this.getInitParameter("password");
                System.out.println(username);
                System.out.println(password);
        }

}

测试

现在调用第二个

• 页面导航
– 请求重定向
• response.sendRedirect(“url”);
– 请求转发
• request.getRequestDispatcher(“url”).forward(request,response);
– 请求包含
• request.getRequestDispatcher(“url”).forward(request,response);

ServletBasic.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

public class ServletBasic extends HttpServlet {

         /**
         * Constructor of the object.
         */
         public ServletBasic() {
                 super();
                System.out.println( "-----ServletBasic-----");
        }

         /**
         * Destruction of the servlet. <br>
         */
         public void destroy() {
                 super.destroy();
                System.out.println( "-----destroy-----");
        }

         /**
         * 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 {
                String username = request.getParameter( "username");
                String password = request.getParameter( "password");
                System.out.println( "username="+username);
                 if(username!= null&&username.equals( "redking")){
                        request.getRequestDispatcher( "/successfull.html").forward(request,response);
                } else{
                        request.getRequestDispatcher( "/failure.html").forward(request,response);
                }
                 /*
                System.out.println("-----doGet-----");

                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 {
                System.out.println( "-----doPost-----");
                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();
        }

        /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */
        public void init() throws ServletException {
                /*
                //第一种方法
                String driver = this.getServletContext().getInitParameter("driver");
                String url = this.getServletContext().getInitParameter("url");
                System.out.println(driver);
                System.out.println(url);
                //第二种方法
                Enumeration enu = this.getServletContext().getInitParameterNames();
                while(enu.hasMoreElements()){
                        String name = (String) enu.nextElement();
                        String value = this.getServletContext().getInitParameter(name);
                        System.out.println(name+":"+value);
                }
                */
                String username = this.getInitParameter("username");
                String password = this.getInitParameter("password");
                System.out.println(username);
                System.out.println(password);
                System.out.println("-----init-----");
        }
        /*
        @Override
        protected void service(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
                // TODO Auto-generated method stub
                System.out.println("-----service-----");
        }
        */
}

successfull.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
< html >
     < head >
         < title >successfull.html </title>
         < meta http-equiv ="keywords" content ="keyword1,keyword2,keyword3" >
         < meta http-equiv ="description" content ="this is my page" >
         < meta http-equiv ="content-type" content ="text/html; charset=UTF-8" >
         <! --<link rel="stylesheet" type="text/css" href="./styles.css">-->

     </head>
     < body >
         < h1 >successfull!!! </h1>
     </body>
</html>

failure.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
< html >
     < head >
         < title >failure.html </title>
         < meta http-equiv ="keywords" content ="keyword1,keyword2,keyword3" >
         < meta http-equiv ="description" content ="this is my page" >
         < meta http-equiv ="content-type" content ="text/html; charset=UTF-8" >
         <! --<link rel="stylesheet" type="text/css" href="./styles.css">-->

     </head>
     < body >
         < h1 >failure!!! </h1>
     </body>
</html>