ServletContext_功能_域物件以及獲取檔案伺服器路徑

域物件：共享資料

　　1.setAttribute(String name,Object  value)

　　2.getAttribute(String name)

　　3.removeAttribute(String name)

ServletContext物件範圍：所有使用者所有請求的資料

儲存資料：

@WebServlet(name = "ServletContextDemo3", value = "/ServletContextDemo3")
public class ServletContextDemo3 extends
 
 HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws
 
 ServletException, IOException {
        /*
        獲取MIME型別：
            MIME型別：在網際網路通訊過程中定義的一種檔案資料型別
      　　　　　　格式：大型別/小型別  text/html　　　image
            方法：
            　　獲取：String  getMimeType(String  file)

            　　2.域物件，共享資料
            　　1.setAttribute(String name,Object  value)
            　　2.getAttribute(String name)
            　　3.removeAttribute(String name)

            　　3.獲取檔案的真實（伺服器）路徑
         
 
*/
        //1.通過HttpServlet物件獲取
        ServletContext context = this.getServletContext();

        //設定資料
        context.setAttribute("msg", "haha");

    }
}

獲取資料

@WebServlet(name = "ServletContextDemo4", value = "/ServletContextDemo4")
public class ServletContextDemo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /*
        獲取MIME型別：
            MIME型別：在網際網路通訊過程中定義的一種檔案資料型別
      　　　　　　格式：大型別/小型別  text/html　　　image
            方法：
            　　獲取：String  getMimeType(String  file)

            　　2.域物件，共享資料
            　　1.setAttribute(String name,Object  value)
            　　2.getAttribute(String name)
            　　3.removeAttribute(String name)

            　　3.獲取檔案的真實（伺服器）路徑
         */
        //1.通過HttpServlet物件獲取
        ServletContext context = this.getServletContext();

       //獲取資料
        Object msg = context.getAttribute("msg");
        System.out.println(msg);
    }
}

ServletContext功能獲取檔案伺服器路徑

獲取檔案的真實（伺服器）路徑

　　方法：String getRealPath(String path)

@WebServlet(name = "ServletContextDemo5", value = "/ServletContextDemo5")
public class ServletContextDemo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext context = this.getServletContext();

        //獲取檔案的伺服器路徑
        String realPath = context.getRealPath("/b.txt");// web目錄下資源訪問
        System.out.println(realPath);


        String c = context.getRealPath("/WEB-INF/c.txt");// WEB-INF目錄下的資源訪問
        System.out.println(c);


        String a = context.getRealPath("/day2_text/src/a.txt");// src目錄下的資源訪問
        System.out.println(a);

    }
}