一、服务器内部转发：request.getRequestDispatcher(“…”).forward(request, response);

一次请求响应的过程，对于客户端而言，内部经过了多少次转发，客户端是不知道的。地址栏中的URL是不会变化的。

内部经过3、4次跳转都是一次请求响应。如图所示：

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二、客户端重定向：response.sendRedirect(“×××”);

两次请求响应的过程。客户端肯定知道请求URL有变化。如图所示：

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三、服务器内部转发代码示例

服务器内部转发：证明可通过代码断点调试

Demo06Servlet.java

// 演示服务器端内部转发
public class Demo06Servlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo06....");
        // 服务器端内部转发
        request.getRequestDispatcher("demo07").forward(request, response);
    }
}

Demo07Servlet.java

public class Demo07Servlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo07....");
    }
}

web.xml

<servlet>
    <servlet-name>Demo06Servlet</servlet-name>
    <servlet-class>com.atguigu.servlets.Demo06Servlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Demo06Servlet</servlet-name>
    <url-pattern>/demo06</url-pattern>
</servlet-mapping>

<servlet>
    <servlet-name>Demo07Servlet</servlet-name>
    <servlet-class>com.atguigu.servlets.Demo07Servlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Demo07Servlet</servlet-name>
    <url-pattern>/demo07</url-pattern>
</servlet-mapping>

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四、客户端重定向代码示例

Demo06Servlet.java

// 演示服务器端内部转发以及客户端重定向
public class Demo06Servlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo06....");
        // 客户端重定向
        response.sendRedirect("demo07");
    }
}

Demo07Servlet.java

public class Demo07Servlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo07....");
    }
}

web.xml

<servlet-mapping>
    <servlet-name>Demo06Servlet</servlet-name>
    <url-pattern>/demo06</url-pattern>
</servlet-mapping>

<servlet>
    <servlet-name>Demo07Servlet</servlet-name>
    <servlet-class>com.atguigu.servlets.Demo07Servlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Demo07Servlet</servlet-name>
    <url-pattern>/demo07</url-pattern>
</servlet-mapping>

访问demo06，一敲回车，可以发现它发送了两次请求

点击demo06的请求，可以发现状态码为302（重定向），Location也变成了demo07

demo07的状态码则是200