Servlet-请求转发

请求转发(forward): 一种在服务器内部的资源跳转方式

实现方式：
写到资源A里
req.getRequestDispatcher("资源B路径").forward(req, resp);

/**
 * 转发
 */
@WebServlet("/req5")
public class RequestDemo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("demo5...");

        // 请求转发
        request.getRequestDispatcher("/req6").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

请求转发资源间共享数据：使用Request对象

• void setAttribute(String name, Object o): 存储数据到request域中
• Object getAttribute(String name): 根据key， 获取值
• void removeAttribute(String name): 根据key, 删除该键值对

// RequestDemo5.java
/**
 * 转发
 */
@WebServlet("/req5")
public class RequestDemo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("demo5...");
        //存储数据
        request.setAttribute("msg", "hello");

        // 请求转发
        request.getRequestDispatcher("/req6").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

// RequestDemo6.java
/**
 * 转发请求
 */
@WebServlet("/req6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("demo6...");

        // 获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

请求转发的特点：

• 浏览器地址栏路径不发生变化
• 只能转发到当前服务器的内部资源
• 一次请求，可以在转发的资源间使用request共享数据