Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之12.Servlet基础(1)

更新时间：2022-06-09 03:34:18

–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################

ServletBasic.java

package com.michael.servlet;

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 ServletBasic extends HttpServlet {

        /**
         * Constructor of the object.
         */
        public ServletBasic() {
                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 {
                // Put your code here
        }

}

web.xml

测试页面

Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之12.Servlet基础(1)

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

• 提交表单的方法
–提交表单的常用方法有两种
• get
–将请求参数显示在URL中
–调用Servlet的doGet方法
• post
–不在URL终显示请求参数
–调用Servlet的doPost方法

login.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
    <head>
        <title>login.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">
        

    </head>
    <body>
        <form name="f1" id="f1" action="/Servlet_Basic/servlet/ServletBasic" method="post">
            <table border="0">
                <tr>
                    <td>帐号:</td>
                    <td><input type="text" name="username" id="login"></td>
                </tr>
                <tr>
                    <td>密码:</td>
                    <td><input type="password" name="password" id="password"></td>
                </tr>
                <tr>
                    <td colspan="2" align="center"><input type="submit" value="登录"></td>
                </tr>
            </table>
        </form>
    </body>
</html>

测试页面

现在将method设置为get

看下测试页面

get会将用户密码显示在url中，而post不会哈~

• Servlet 生命周期
–Servlet生命周期的四个步骤
• 加载实例化Servlet
–创建一个Servlet实例
• 调用init方法
–仅被调用一次
• 调用service方法（doGet或者doPost)
–被调用多次（每次请求调用）
• 调用destory方法
–调用一次（销毁Servlet）

ServletBasic.java

package com.michael.servlet;

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

}

输入信息进行登录

页面调用Servlet

现在我们再重新登录下,Servlet重新执行了一次doGet或者doPost方法，而不会重新构造及初始化Servlet

doGet或者doPost方法最终都会调用service方法,我们测试下，先覆盖service方法

ServletBasic.java

重新部署tomcat后执行登录操作

现在Servlet不再调用doGet或者doPost方法而直接调用service方法

• 使用Servlet 输出HTML页面
–获得输出流
• PrintWriter out = response.getWriter();
–输出HTML页面

• 获得Servlet初始化参数
–获得全局参数
• 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>
        <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>ServletBasic</servlet-name>
        <servlet-class>com.michael.servlet.ServletBasic</servlet-class>
    </servlet>

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

</web-app>

ServletBasic.java

package com.michael.servlet;

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 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 {
                String driver = this.getServletContext().getInitParameter("driver");
                String url = this.getServletContext().getInitParameter("url");
                System.out.println(driver);
                System.out.println(url);
                System.out.println("-----init-----");
        }

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

重新登录测试下

还可以使用第二种方法

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);
                }
                System.out.println("-----init-----");
        }

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

执行登录进行测试

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

附件：http://down.51cto.com/data/2353091

本文转自redking51CTO博客，原文链接：http://blog.51cto.com/redking/168296，如需转载请自行联系原作者

上一篇 : ：[零基础学JAVA]Java SE应用部分-34.Java常用API类库下一篇 : InputStream、OutputStream、String的相互转换(转)

Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之12.Servlet基础(1)

相关阅读

推荐文章