在以前的servlet中我们初始化一些参数都是配置在web.xml中的，自从servlet3.0之后给我们提供了注解@WebServlet和@WebInitParam，@WebServlet是用来配置servlet的属性的，@WebInitParam是用来配置一些初始化属性的。

@WebServlet和@WebInitParam使用如下：

package roseindia.net;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(
  name = "WebInitParamExample", urlPatterns = {"/hello"}
  ,initParams = {
  @WebInitParam(name= "Site :", value="http://roseindia.net"),
  @WebInitParam(name= "Rose", value= "India"),
  }
)
public class WebInitParamExample extends HttpServlet{
  public void doGet(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException
  {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.println("<h2>Init Param Servlet Example</h2>");
    ServletConfig config= getServletConfig();
    String pValue= config.getInitParameter("Site :");
    out.println("Param Value : "+pValue);
    String pValue1= config.getInitParameter("Rose");
    out.println("<br>Param Value : "+pValue1);
    out.close();
  }
}


如果在web.xml中配置则如下： 

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" 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">
  <display-name>servletAnnotationExample</display-name>
  <servlet>
    <servlet-name>WebInitParamExample</servlet-name>
    <servlet-class>roseindia.net.WebInitParamExample</servlet-class>
    <init-param>
      <param-name>Site :</param-name>
      <param-value>http://roseindia.net</param-value>
    </init-param>
  </servlet>
  <servlet-mapping>
    <servlet-name>WebInitParamExample</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>
</web-app>