ServletContext对象

心已赠人 2024-04-18 16:02 63阅读 0赞

### 文章目录 ###

*  获取对象
 *  获取MIME类型
 *  域对象：共享数据
 *  获取文件的服务器路径

*  概念：代表整个web应用，可以和程序的容器(服务器)来通信
 *  功能：
    
     *  获取MIME类型
     *  是一个域对象，可以用来共享数据
     *  获取文件的真实路径（服务器路径）

# 获取对象 #

*  两种方法：
    
     *  通过request对象获取
     *  通过httpservlet对象获取
 *  实践

# 获取MIME类型 #

*  MIME类型：在互联网通信过程中定义的一种文件数据类型
    
     *  格式：大类型/小类型 ----- 如text/html；image/jpeg
 *  实践：

package cn.oceanstart.web;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet("/ServletContext")
    public class ServletContext extends HttpServlet {
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
           //1、获取对象
            javax.servlet.ServletContext context = this.getServletContext();
    
            //2、定义文件名称
            String filename = "a.jpg";
    
            //3、获取MIME类型
            String mimeType = context.getMimeType(filename);
            System.out.println(mimeType);   //image/jpeg
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request, response);
        }
    }

# 域对象：共享数据 #

*  ServletContext对象范围：共享所有用户所有请求的数据，范围是最大的
 *  项目目录：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70]  
    ServletContextDemo1内容：

ServletContextDemo2内容

浏览器访问：

<http://localhost:8080/Response\_war\_exploded/ServletContextDemo1

然后访问:http://localhost:8080/Response\_war\_exploded/ServletContextDemo2

# 获取文件的服务器路径 #

项目路径：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70 1]  
ServletContextDemo1内容：

package cn.oceanstart.web;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.File;
    import java.io.IOException;
    
    @WebServlet("/ServletContextDemo1")
    public class ServletContextDemo1 extends HttpServlet {
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
           //1、获取对象
            javax.servlet.ServletContext context = this.getServletContext();
    
            //2、获取文件的服务器路径
            String realPath = context.getRealPath("/b.txt");  //web目录下资源访问
            System.out.println(realPath); //E:\workspace\Demo\out\artifacts\Response_war_exploded\b.txt
    
            //WEB-INFO目录下的资源访问
            System.out.println(context.getRealPath("/WEB-INF/c.txt"));// E:\workspace\Demo\out\artifacts\Response_war_exploded\WEB-INF\c.txt
    
            //src目录下的资源访问
            System.out.println(context.getRealPath("/WEB-INFO/classes/a.txt")); //E:\workspace\Demo\out\artifacts\Response_war_exploded\WEB-INFO\classes\a.txt
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request, response);
        }
    }

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/a9bee3661e8a49f2a3979f1d40bba902.png