利用反射优化Servlet抽象出父类BaseServlet

　　在编写servlet的时候发现每个servlet里面的doPost方法都如：

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doGet(request, response);

    }

　　而在doGet方法中大多是对uri的跳转

　　(通过在uri后面加上method参数可以定位到不同的方法，这样就可以少写一些servlet了)

　　如果新增模块，则该模块的Servlet中也同样包含相同的代码，因此，代码过度冗余，需要优化。

protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        //获取客户端请求的方法名

        String methodName = request.getParameter("method");

        //根据名称判断调用的方法

        if("categoryList".equals(methodName))

        {

            categoryList(request,response);

        }else if("index".equals(methodName))

        {

            index(request,response);

        }else if("productInfo".equals(methodName))

        {

            productInfo(request,response);

        }else if("productList".equals(methodName))

        {

            productList(request,response);

        }

    }

　　抽象出父类BaseServlet，并且在BaseServlet中使用反射机制实现方法的调用

public class BaseServlet extends HttpServlet {

    private static final long serialVersionUID = 7978401768598506854L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        //1.获取方法名

        String methodName = request.getParameter("method");

        //2.得到请求Servlet的字节码

        Class clazz = this.getClass();

        try {

            //3.根据字节码和方法名获取方法对象 所有方法参数均为HttpServletRequest和HttpServletResponse类型

            Method method = clazz.getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.setAccessible(true);   //设置方法均直接访问

            //4.调用method方法,实现其中的功能

            method.invoke(this, request, response);

        } catch (NoSuchMethodException e) {

            e.printStackTrace();

        } catch (SecurityException e) {

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            e.printStackTrace();

        }

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doGet(request, response);

    }}

　　然后再写servlet就只用写具体的方法就行了

@WebServlet("/user")

@SuppressWarnings("unused")

public class UserServlet extends BaseServlet {

    private static final long serialVersionUID = 7665438418738590582L;

    private UserService userService = new UserServiceImpl();

    //安全退出

    private void logout(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        request.getSession().invalidate();

        //涉及 - cookie  - 清除cookie

        response.sendRedirect(request.getContextPath() + "/index");

    }

    //用户登录

    private void login(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String username = request.getParameter("username");

        String password = request.getParameter("password");

        //自动登录  -  记住用户名

        User user = userService.login(username, password);

        if(user != null) {   //成功

            request.getSession().setAttribute("user", user);

            response.sendRedirect(request.getContextPath() + "/index");

        } else {

            request.setAttribute("info", "用户名或密码错误!");

            request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);

        }

    }

    //email - 账号激活

    private void active(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String activeCode = request.getParameter("activeCode");

        userService.active(activeCode);

        request.setAttribute("info", "账号激活成功， 请登录！");

        request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);

    }

    /**

    * @Title: register

    * @Description: 用户注册

    */

    private void register(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        //调用service

        Map<String, String[]> paramMap = request.getParameterMap();

        userService.register(paramMap);

        //跳转至首页|登录页面

        request.getRequestDispatcher("/WEB-INF/jsp/registerSuccess.jsp").forward(request, response);

    }

}

巴特西

利用反射优化Servlet抽象出父类BaseServlet

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