javaweb Servletconfig和Servletcontext

￡神魔★判官ぃ 2023-06-06 12:27 2阅读 0赞

Servletconfig：在servlet的配置文件web.xml中，可以使用多个标签，作为servlet初始化的参数  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU5OTM3Nw_size_16_color_FFFFFF_t_70]  
配置是在相应的类中去配置的

package com.j2ee.servlet;
    
    import java.io.IOException;
    import java.util.Enumeration;
    
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class LoginServerlt extends HttpServlet{
    	
    	private ServletConfig sc;
    	public void init(ServletConfig config) throws ServletException{
    		this.sc=config;
    		//遍历init的所有内容
    		Enumeration<String> e=this.sc.getInitParameterNames();
    		while(e.hasMoreElements()) {
    			String name=e.nextElement();
    			String value=this.sc.getInitParameter(name);
    			System.err.println(name+"---"+value);
    		}
    	}
    	
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		//b)servlet的config初始化
    		if (userName==null || userName.equals("")) {
    			//从config中默认取值
    			userName=this.sc.getInitParameter("name");
    			password=this.sc.getInitParameter("password");
    		}else {
    			System.out.println("已经取到其他值了");
    		}
    	}
    	
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req, resp);
    	}
    	
    }

**2 Servletcontext**

Servletcontext代表当前应用，web容器在启动的时候，会给每个应用都创建一个servletcontext对象，context的引用被config持有（维护），可以通过config.getContext的方式获取context对象，由于所有servlet都使用同一个context，通常用来做通讯使用，可称为context域  
![在这里插入图片描述][20191011220746539.png]  
![在这里插入图片描述][20191011220757832.png]  
![在这里插入图片描述][20191011220805833.png]  
**2.1 在配置中给整个web应用做配置**  
![在这里插入图片描述][20191011220835264.png]  
**2.2 e) Context如何实现两个servlet的跳转功能？RequestDispatcher**  
![在这里插入图片描述][20191011220907857.png]  
![在这里插入图片描述][20191011220917599.png]

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[20191011220746539.png]: /images/20230601/63bbc3e2402e40d790925185460f1710.png
[20191011220757832.png]: /images/20230601/d7fbdd1a45614b30a5a5d34d74654fe7.png
[20191011220805833.png]: /images/20230601/926dd92724b64351b8ad135db427c260.png
[20191011220835264.png]: /images/20230601/ea791034ee2d470785a405a800101dce.png
[20191011220907857.png]: /images/20230601/518400b9c4774290bafe04071fc0dda5.png
[20191011220917599.png]: /images/20230601/976f1f26249a4c5bb64fe1cdbe9b9af0.png