JavaWeb-ServletContext的四种使用实例

共享数据

HelloServlet.Java

public class HellowServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();

        String username = "小梁";
        context.setAttribute("username",username);
    }

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

ServletDispatcher.Java

public class ServletDispatcher extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        context.getRequestDispatcher("/getP").forward(req,resp);
    }

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

web.xml

  <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>com.teng.servlet.HellowServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>getC</servlet-name>
    <servlet-class>com.teng.servlet.GetServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>getC</servlet-name>
    <url-pattern>/getC</url-pattern>
  </servlet-mapping>

获取初始化参数

GetParameter.Java

public class GetParameter extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String url = context.getInitParameter("url");
        resp.getWriter().println(url);
    }

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

web.xml

<context-param>
    <param-name>url</param-name>
    <param-value>jdbc:mysql://localhost:3306/digital</param-value>
  </context-param>
  <servlet>
    <servlet-name>getP</servlet-name>
    <servlet-class>com.teng.servlet.GetParameter</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>getP</servlet-name>
    <url-pattern>/getP</url-pattern>
  </servlet-mapping>

请求转发页面

ServletDispatcher.Java

public class ServletDispatcher extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        context.getRequestDispatcher("/getP").forward(req,resp);
    }

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

web.xml

  <servlet>
    <servlet-name>getD</servlet-name>
    <servlet-class>com.teng.servlet.ServletDispatcher</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>getD</servlet-name>
    <url-pattern>/getD</url-pattern>
  </servlet-mapping>

读取资源文件

GetProperties.Java

public class GetProperties extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        InputStream is = context.getResourceAsStream("/WEB-INF/classes/db.properties");
        resp.setCharacterEncoding("utf-8");

        Properties prop = new Properties();
        prop.load(is);
        String un = prop.getProperty("username");
        String pwd = prop.getProperty("password");
        resp.getWriter().print("用户名为:"+ un +",密码为:"+ pwd);
    }

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

web.xml

 <servlet>
    <servlet-name>getpro</servlet-name>
    <servlet-class>com.teng.servlet.GetProperties</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>getpro</servlet-name>
    <url-pattern>/getpro</url-pattern>
  </servlet-mapping>