ServletConfig学习

• • 1.ServletConfig是什么？
  • 2.ServletConfig对象

1.ServletConfig是什么？

获得servlet相关配置的对象（获取xml里面的内容）

2.ServletConfig对象

在xml（servlet)配置：

 <init-param>
            <param-name>username</param-name>
            <param-value>root</param-value>
        </init-param>//通过：username索引，得到value 值：root
        //可以在创建ServletConfig对象，中获得索引，进而获得value值
        //ServletConfig config=this.getServletConfig();//创建对象ServletConfig
     //   String username=config.getInitParameter("username");//得到配置里面的值

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">






    <servlet>
        <servlet-name>demo2</servlet-name>
        <servlet-class>com.example.demo16.HelloServlet2</servlet-class>





        <load-on-startup>1</load-on-startup>


    </servlet>


<servlet-mapping>
    <servlet-name>demo2</servlet-name>
    <url-pattern>/hello</url-pattern>

</servlet-mapping>


    <servlet>
        <servlet-name>demo3</servlet-name>
        <servlet-class>com.example.demo16.HelloSerrvlet3</servlet-class>

        <init-param>
            <param-name>username</param-name>
            <param-value>root</param-value>
        </init-param>

        <init-param>
            <param-name>password</param-name>
            <param-value>abc</param-value>
        </init-param>

    </servlet>


    <servlet-mapping>
        <servlet-name>demo3</servlet-name>
        <url-pattern>/helloo</url-pattern>
    </servlet-mapping>



</web-app>

创建类
HelloSerrvlet3 extends HttpServlet :

使用doget方法：
里面再使用
ServletConfig config=this.getServletConfig();//创建ServletConfig对象
String username=config.getInitParameter(“username”);//得到配置里面的值
使用了：ServletConfig的API:getInitParameter();
获得配置里面的值

package com.example.demo16;


import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class HelloSerrvlet3 extends HttpServlet {


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //super.doGet(req, resp);
        resp.getWriter().println("helloWolrd!");
        ServletConfig config=this.getServletConfig();//创建对象ServletConfig
        String username=config.getInitParameter("username");//得到配置里面的值

        String password=config.getInitParameter("password");//也得到了
        System.out.println(username+"  "+password);
        
        
        
        
        

    }


    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

效果：

每访问一次，就执行一次doget方法
root abc

获得所有参数：
Enumeration

Enumeration<String> names=config.getInitParameterNames();//获得所有参数值
        while (names.hasMoreElements()){//遍历

            String name=names.nextElement();//获取：name值
            String value=config.getInitParameter(name);//获取name对于的value值
            System.out.println(name+" "+value);

        }

获取：名称

        String servletName=config.getServletName();//获类取名称
        System.out.println(servletName);//获取了xml这里面 <servlet-name>demo3</servlet-name>的名称