作业一：servlet技术及应用
servlet技术及应用
- 1.Servlet将请求转发给另一个Servlet的方法。
- 1.input.html
- 2.com.demo.Student类
- 3.FirstServlet
- 4.SecondServlet
- 2.使用ServletConfig检索Servlet的初始化参数。
- 1.ConfigDemoServlet
- 3.为ServletContext配置初始化参数
- 1.在Web.xml中：
- 4.编写一个名为CountServlet的Servlet程序：
- 1.CountServlet
1.Servlet将请求转发给另一个Servlet的方法。
【步骤1】创建一个名为input.html的HTML页面，其中包括一个表单，表单中包含两个文本域，分别供用户输入学号和姓名，该页面也包含提交和重置按钮。
【步骤2】 定义一个名为com.demo.Student类，其中包括学号sno和姓名name两个private的成员变量，定义访问和修改sno和name的方法。
【步骤3】编写名为FirstServlet的Servlet，要求当用户在input.html中输入信息后点击“提交”按钮，请求FirstServlet对其处理。在FirstServlet中使用表单请求参数（学号和姓名）创建一个Student对象并将其作为属性存储在请求作用域中，然后通过请求对象的getRequestDispatcher()方法获得RequestDispatcher()对象，将请求转发到SecondServlet。
【步骤4】在SecondServlet中取出请求作用域中存储的Student对象，并显示输出该学生的学号和姓名，5秒钟之后，自动返回input.html页面。
1.input.html
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="FirstServlet" method="get">
学号：<input name="username"><br>
<br>
姓名：<input name="password"><br>
<br>
<input type="submit" value="登录 "/>
<input type="submit" value="取消">
</form>
</body>
</html>
2.com.demo.Student类
package com.demo;
public class Student {
private String sno;
private String name;
public Student(String sno, String name) {
// TODO Auto-generated constructor stub
this.sno=sno;
this.name=name;
}
public String getSno() {
return sno;
}
public void setSno(String sno) {
this.sno = sno;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
3.FirstServlet
package com.demo;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/FirstServlet")
public class FirstServlet extends HttpServlet {
protected void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
String sno = request.getParameter("sno");
String name = request.getParameter("sname");
Student student = new Student(sno,name);
request.setAttribute("student", student);
RequestDispatcher rd = request.getRequestDispatcher("/SecondServlet");
rd.forward(request, response);
}
}
4.SecondServlet
package com.demo;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/SecondServlet")
public class SecondServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Student student= (Student)request.getAttribute("student");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.println("学生信息 ");
out.println("学号："+student.getSno()+"
");
out.println("姓名："+new String(
student.getName().getBytes("iso-8859-1"),"UTF-8")+"
");
//out.println("返回输入页面");
response.setHeader("Refresh","5;url=input.html");
}
}
2.使用ServletConfig检索Servlet的初始化参数。
【步骤1】编写ConfigDemoServlet程序，通过注释为其添加初始化参数email、telephone,在Servlet中读取该servlet的名称和初始化参数email、telephone，并将这两个参数的值在响应的HTML文本中输出。
【步骤3】在浏览器的地址栏中输入下面URL请求该Servlet：
http://localhost:8080/ homework01/configDemo.do
1.ConfigDemoServlet
package com.demo;
import java.io.*;
import javax.servlet.*;
import javax.servlet.annotation.*;
import javax.servlet.http.*;
@WebServlet(name="ConfigDemoServlet",
urlPatterns = {"/config-demo"},
initParams = {
@WebInitParam(name = "email", value = "[email protected]"),
@WebInitParam(name = "telephone", value = "8899123")
})
public class ConfigDemoServlet extends HttpServlet{
String servletName = null;
ServletConfig config = null;
String email = null;
String telephone = null;
String admin_email=null;
String admin_tel=null;
private ServletContext servletContext;
public void init(ServletConfig config) {
this.config = config;
servletName = config.getServletName();
email = config.getInitParameter("email");
telephone = config.getInitParameter("telephone");
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException,IOException{
response.setContentType("text/html;charset=UTF-8");
//写入日志文件
this.servletContext=config.getServletContext();
String admin_email = servletContext.getInitParameter("admin-email");//利用名字获取值
String admin_tel = servletContext.getInitParameter("admin-tel");//利用名字获取值
PrintWriter out = response.getWriter();
out.println("");
out.println("配置对象 ");
out.println("Servlet名称："+servletName+"
");
out.println("Email地址："+email+"
");
out.println("电话："+telephone);
out.println("");
out.println("
");
out.println("web.xml文件中的初始化参数值admin-email: " + admin_email);
out.println("
");
out.println("web.xml文件中的初始化参数值admin-tel: " + admin_tel);
}
}
3.为ServletContext配置初始化参数
在web.xml文件中为当前web应用添加两个名为admin-email和admin-tel的ServletContext初始化参数，在ConfigDemoServlet中获取这两个参数的参数值，使用ServletContext对象将admin-email和admin-tel的参数值写入日志文件中，并查看日志文件。
1.在Web.xml中：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<display-name>homework1</display-name>
<!-- 配置初始化参数 -->
<context-param>
<param-name>admin-email</param-name>
<param-value>hacker@163.com</param-value>
</context-param>
<context-param>
<param-name>admin-tel</param-name>
<param-value>8899123</param-value>
</context-param>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
</web-app>
4.编写一个名为CountServlet的Servlet程序：
1）使用成员变量保存该Servlet被访问的次数，试打开多个浏览器窗口模拟多个用户同时访问该Servlet，观察该Servlet被访问次数的变化。
2）修改该Servlet，通过ServletContext属性保存被多用户同时访问的次数，体会用ServletContext在应用作用域共享数据的方法。
1.CountServlet
package com.demo;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class countServlet1
*/
@WebServlet("/CountServlet")
public class CountServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public CountServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置字符编码
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=utf-8");
//获取全局的共享数据
ServletContext servletContext = this.getServletContext();
//获取计数器count
Integer count = (Integer) servletContext.getAttribute("count");
//如果获取的计算器对象为空 ，说明是第一次访问，并将count，放入servletCount
if( servletContext.getAttribute("count") == null) {
count = 1;
servletContext.setAttribute("count", count);
}else {
//否则就不是第一次访问，将登陆的计数器进行加1的数据更新
servletContext.setAttribute("count", count+1);
}
//将登陆的次数显示在页面上
PrintWriter out =response.getWriter();
out.print("\r\n" +
"\r\n" +
"\r\n" +
"\r\n" +
"登陆网页次数统计 \r\n" +
"\r\n" +
"");
out.print(""
);
out.print("您是第 "+ servletContext.getAttribute("count")+"位访客");
out.print(""
);
out.print("\r\n" +
"");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}