javaweb——ServletContext应用

1.获取初始化参数创建一个ServletDemo03类

package com.kuang.servlet;

import javax.servlet.ServletContext;
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 ServletDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();

//        context.setInitParameter("myName","ServletDemo");

        String url = context.getInitParameter("url");
//        String myName = context.getInitParameter("myName");

        resp.getWriter().print(url);
//        resp.getWriter().print("项目名称："+myName);


    }

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

web.xml


  
    url
    jdbc:mysql://localhost:3306/mybatis
  


    gp
    com.kuang.servlet.ServletDemo03
  
  
    gp
    /gp

2.请求转发请求转发流程

请求转发与重定向

创建一个ServletDemo04类

package com.kuang.servlet;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
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 ServletDemo04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        System.out.println("进入了ServletDemo04");
        //       getRequestDispatcher请求转发，参数为转发地址"/gp","/"代表当前项目，”gp“代表转发到gp请求
//        RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp");//转发的请求路径
//        requestDispatcher.forward(req,resp);//调用forward方法实现请求转发

        context.getRequestDispatcher("/gp").forward(req,resp);
    }

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

web.xml

 
    sd4
    com.kuang.servlet.ServletDemo04
  
  
    sd4
    /sd4

3.读取资源文件

Properties

在Java目录下新建properties
在resources目录下新建properties

发现：都被打包到同一路径下：classes，我们俗称这个路径为类路径。即classpath

db.properties

username=ziyu
password=123456

创建一个ServletDemo05 类

package com.kuang.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class ServletDemo05  extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
//        getResourceAsStream将资源转换为一个流,/WEB-INF/classes/db.properties代表相对定位
        InputStream is = context.getResourceAsStream("/WEB-INF/classes/db.properties");
 //       InputStream is = context.getResourceAsStream("/WEB-INF/classes/com/kuang/servlet/aa.properties");
        Properties properties = new Properties();

//        加载一个流
        properties.load(is);
        String username = properties.getProperty("username");
        String password = properties.getProperty("password");
        resp.getWriter().print(username+":"+password);
    }

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

web.xml


    sd5
    com.kuang.servlet.ServletDemo05
  
  
    sd5
    /sd5

4.共享数据

https://blog.csdn.net/Silly011/article/details/124671629

javaweb——ServletContext应用

Java相关栏目本月热门文章