javaWeb——Servlet中getInitParameter()的使用

1、容器初始化一个servlet时，会为这个servlet建一个唯一的ServletConfig
2、容器从web.xml读出Servlet初始化参数，并把这些参数交给ServletConfig，然后把ServletConfig传递给servlet的init(ServletConfig config)方法。
3、容器只有在创建servlet实例时才会读DD文件中的init-param, 并且在servlet一生中只读一次。
4、方法:
getInitParameter(String name)：根据给定的初始化参数，返回匹配的初始化参数值。
getInitParameterNames()：返回一个Enumeration对象，里面包含了所有的初始化参数。
getServletContext()：返回一个servletContext()对象.
getServletName()：返回servlet的名字，即web.xml中的的子元素的值。如果没有配置这个子元素，则返回servlet类的名字。

  MyServlet //文件名
  
    index.html
    index.htm
    index.jsp
    default.html
    default.htm
    default.jsp
  
  
      
   Myservlet //类名
     
   servlet.com.Myservlet   
     
      name
      admin
    
       
      psd
      123456
    
  
  
  
  Myservlet //类名
  /Myservlet/Myservlet   路径:/项目名/类名
   
  

package servlet.com;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
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;


//@WebServlet(
//		asyncSupported = true, 
//		urlPatterns = { "/Myservlet" }, 
//		initParams = { 
//				@WebInitParam(name = "name", value = "admin"), 
//				@WebInitParam(name = "psd", value = "123456")
//		}
//		)

//@WebServlet("/Myservlet")  
public class Myservlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    
    public Myservlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		
		 PrintWriter out = response.getWriter();
		 response.setHeader("Content-type","text/html; charset=UTF-8");
		 ServletConfig cfg = getServletConfig();
		 String username  = cfg.getInitParameter("name");
		 String password  = cfg.getInitParameter("psd");
	     out.println("name: "+username);
	     out.println("psd: "+password);
	}

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}