獲取上下文初始化參數(shù)的相關(guān)方法

創(chuàng)建ServletContext對象  

1）通過 GenericServlet 提供的 getServletContext() 方法

//通過 GenericServlet的getServletContext方法獲取ServletContext對象
ServletContext servletContext = this.getServletContext();

2）通過 ServletConfig 提供的 getServletContext() 方法

//通過 ServletConfig的 getServletContext方法獲取ServletContext對象
ServletContext servletContext = this.getServletConfig().getServletContext();

//通過 Config的 getServletContext方法獲取ServletContext對象
ServletContext context = config.getServletContext();

3）通過 HttpSession 提供的 getServletContext() 方法

//通過 Session的 getServletContext方法獲取ServletContext對象
ServletContext context = req.getSession().getServletContext();

4）通過 HttpServletRequest 提供的 getServletContext() 方法

//通過 HttpServletRequest的 getServletContext方法獲取ServletContext對象
ServletContext servletContext = req.getServletContext();

上下文初始化參數(shù)

局部參數(shù)

    <servlet>
        <init-param>
            <param-name>name</param-name>
            <param-value>Lungcen</param-value>
        </init-param>
        <init-param>
            <param-name>password</param-name>
            <param-value>110120130</param-value>
        </init-param>
    </servlet>

全局參數(shù)

    <context-param>
        <param-name>姓名</param-name>
        <param-value>Lungcen</param-value>
    </context-param>
    <context-param>
        <param-name>年齡</param-name>
        <param-value>19</param-value>
    </context-param>

 獲取ServletContext的全局參數(shù)

Enumeration<String> names = this.context.getInitParameterNames();
        
        while (names.hasMoreElements())
        {
            String s = names.nextElement();
            writer.write(s + "->" + context.getInitParameter(s) + "<br/>");
        }

ServletContext 屬性與上下文初始化參數(shù)對比

實現(xiàn)數(shù)據(jù)通訊

在 Servlet 中，調(diào)用 ServletContext 接口的 setAttribute() 方法可以創(chuàng)建一些屬性，這些屬性被存 放在 ServletContext 對象中。應(yīng)用中所有 Servlet 都可以對這些屬性進行訪問和操作，通過它們可以實現(xiàn)應(yīng)用內(nèi)不同 Servlet 之間的數(shù)據(jù)通訊。

數(shù)據(jù)通訊的程序?qū)嵗?/h3>

package com.zpark.servlet;
 
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;
import java.io.PrintWriter;
 
@WebServlet(urlPatterns = "/LLL.do")
public class MyServlet04 extends HttpServlet {
 
    @Override
    public void init() throws ServletException {
        getServletContext().setAttribute("count", 0);
    }
 
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        Integer count = (Integer) getServletContext().getAttribute("count");
        count++;
        getServletContext().setAttribute("count", count);
 
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();
        writer.write("歡迎來到界面" + count);
        writer.close();
    }
 
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        doGet(req, resp);
    }
}

package com.zpark.servlet;
 
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;
import java.io.PrintWriter;
 
@WebServlet("/Lun5.do")
public class MyServlet05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();
        Integer count = (Integer) getServletContext().getAttribute("count");
        writer.write("今天是一個好日子" + count);
        writer.close();
    }
 
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) 
throws ServletException, IOException {
        resp.setCharacterEncoding("utf-8");
        doGet(req, resp);
    }
}

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