Servlet学习笔记—ServletConfig参数配置与获取

一、ServletConfig参数配置

在web.xml文件的<servlet>节点中加入节点<init-param>：

<init-param>
<param-name>username</param-name>
<param-value>123456</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>111111</param-value>
</init-param>

整个web.xml文件如下：

<?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">
<!-- 第一步：配置servlet信息 -->
<servlet>
<!-- 设置servlet的名字 -->
<servlet-name>httpServlet</servlet-name>
<!-- 具体的servlet的类，要填上包的全路径 -->
<servlet-class>com.pl.servlet.HttpServletDemo1</servlet-class>
<!-- 设置初始化参数，通过ServletConfig来获得 -->
<init-param>
<param-name>username</param-name>
<param-value>123456</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>111111</param-value>
</init-param>
<!-- 设置servlet的初始化的时机在服务器启动的时候 -->
<load-on-startup>1</load-on-startup>
</servlet>
<!-- 第二步：配置servlet映射信息 -->
<servlet-mapping>
<!-- 指定要映射的servlet的名字 -->
<servlet-name>httpServlet</servlet-name>
<!-- servlet的具体映射路径 -->
<url-pattern>/httpserv</url-pattern>
</servlet-mapping>
</web-app>

二、ServletConfig参数获取

你不能自己去创建ServletConfig对象，Servlet的init(ServletConfig config)方法的参数就是ServletConfig类型的。Tomcat在调用init(ServletConfig config)方法时，会传递ServletConfig对象。你可以在init(ServletConfig config)方法中使用它！

代码如下：

public class HttpServletDemo1 extends HttpServlet {

@Override
public void init(ServletConfig config) throws ServletException {
System.out.println("做一些初始化的工作");
//通过指定参数名称获取参数值
String username = config.getInitParameter("username");
System.out.println(username);
//通过指定参数名称获取参数值
String password = config.getInitParameter("password");
System.out.println(password);
//获取所有的参数名称，然后根据参数名称获取对应的参数值
Enumeration<String> emun = config.getInitParameterNames();
while(emun.hasMoreElements()) {
String nextElement = emun.nextElement();
String initParameter = config.getInitParameter(nextElement);
System.out.println(nextElement+":"+initParameter);
}
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("doGet方法被调用了");
resp.getOutputStream().write("doGet方法被调用了".getBytes());
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("doPost方法被调用了");
resp.getOutputStream().write("doPost方法被调用了".getBytes());
}
}