一、servlet初始化参数
使用标签初始化的参数是被应用程序中所有的servlet所共享。但是有时候我们需要为某一个特定的servlet配置参数,这个时候我们就需要使用servlet初始化参数。下边介绍两种servlet参数初始化的方法。
- (1)配置web.xml文件
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。
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>homework01</display-name>
<!-- 配置servlet -->
<servlet>
<servlet-name>ConfigDemoServlet</servlet-name>
<servlet-class>com.configDemo.ConfigDemoServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ConfigDemoServlet</servlet-name>
<url-pattern>/configDemo.do</url-pattern>
</servlet-mapping>
<!-- 配置整个web应用的初始化参数 -->
<context-param>
<param-name>admin-email</param-name>
<param-value>123456@qq.com</param-value>
</context-param>
<context-param>
<param-name>admin-tel</param-name>
<param-value>1234567890</param-value>
</context-param>
</web-app>
- (2)使用注解完成servlet初始化参数:
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在页面上。- 下边代码所演示的是注释进行servlet的参数初始化:
@WebServlet(
name = "ConfigDemoServlet",
urlPatterns="/configDemo.do",
initParams = {
@WebInitParam(name= "email", value="telephone")
})
二、完整代码如下:
package com.configDemo;
import java.io.FileReader;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class ConfigDemoServle
* servlet的注释初始化
*/
@WebServlet(
name = "ConfigDemoServlet",
urlPatterns="/configDemo.do",
initParams = {
@WebInitParam(name= "email", value="telephone")
})
public class ConfigDemoServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
//ServletContext 的应用:作为整个web范围中的共享数据
private ServletContext servletContext;
/**
* @see HttpServlet#HttpServlet()
*/
public ConfigDemoServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=utf-8");
//获取servlet参数
ServletConfig config = this.getServletConfig();
Enumeration<String> enumeration = config.getInitParameterNames();
String name = (String) enumeration.nextElement();//获取对应的值
String value11 = config.getInitParameter(name);//利用名字获取值
//将信息打印在界面上
response.getWriter().println("servlet名称 : "+ config.getServletName());
response.getWriter().println("<br><br>");
response.getWriter().println("Email 地址: "+ name);
response.getWriter().println("<br><br>");
response.getWriter().println("电话号码:" + value11);
response.getWriter().println("<br><br>");
//获取web.xml文件中的初始化参数值,并且显示在页面上
this.servletContext = config.getServletContext();
String adminEmail = servletContext.getInitParameter("admin-email");//利用名字获取值
String adminTel = servletContext.getInitParameter("admin-tel");//利用名字获取值
response.getWriter().println("web.xml文件中的初始化参数值admin-email: " + adminEmail);
response.getWriter().println("<br><br>");
response.getWriter().println("web.xml文件中的初始化参数值admin-tel: " + adminTel);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
三、页面显示结果