[开发测试]3.bean_mvc_过滤器监听器

JavaBean

实体类

JavaBean有特定写法:

• 必须有无参构造
• 属性必须私有
• 必须有对应的get/set方法

一般用来和数据库的字段做映射 ORM

ORM:对象关系映射

• 表—>类
• 行记录—>对象
• 字段—>属性

MVC三层架构

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Model

• 业务处理:业务逻辑(Service)
• 数据持久层:CRUD(Dao)

View

• 展示数据
• 提供链接发起Servlet请求(a,form,img…)

Controller (Servlet)

• 接收用户的请求:(req:请求参数、Session信息…)

• 交给业务层处理对应的代码

• 控制视图的跳转

  登录--->接收用户的登录请求--->处理用户的请求（获取用户登录的参数，username，password )---->交给业务层处理登录业务（判断用户名密码是否正确5 --->Dao层查询用户名和密码是否正确
  

Filter(重点)

shiro:使用filter实现

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public class ShowFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("init...........");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=UTF-8");
        System.out.println("执行前");
        chain.doFilter(request,response); //必须执行过滤器同行
        System.out.println("执行后");
    }

    @Override
    public void destroy() {
        System.out.println("destory..............");
    }
}

    <servlet-mapping>
        <servlet-name>showHello</servlet-name>
        <url-pattern>/show</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>showHello</servlet-name>
        <servlet-class>com.learn.cs.ShowHello</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>showHello2</servlet-name>
        <url-pattern>/cs/show</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>showHello2</servlet-name>
        <servlet-class>com.learn.cs.ShowHello</servlet-class>
    </servlet>

    <filter>
        <filter-name>showFilter</filter-name>
        <filter-class>com.learn.filter.ShowFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>showFilter</filter-name>
        <url-pattern>/cs/show</url-pattern>
    </filter-mapping>

监听器

public class MyListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("创建会话:"+se.getSession().getId());
        ServletContext sc = se.getSession().getServletContext();
        Integer personCount = (Integer) sc.getAttribute("count");
        if(personCount==null)
        {
            personCount =1;
        }
        else
        {
            personCount = personCount+1;
        }
        sc.setAttribute("count",personCount);
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("销毁会话:"+se.getSession().getId());
    }
}

    <listener>
        <listener-class>com.learn.listener.MyListener</listener-class>
    </listener>

过滤器\监听器常见应用

监听器:GUI编程

过滤器拦截登录,访问页面请求

-class>com.learn.listener.MyListener

# 过滤器\监听器常见应用

监听器:GUI编程

过滤器拦截登录,访问页面请求