聊天室收发信息

要自己做一个聊天室

在这里写下思路

聊天室，首先就是要有信息的收发

也就是收集和显示

信息显示
chatinfo.jsp

<body>
    <table align="center" cellspacing="10">
        <tr>
            <td colspan="3"><textarea rows="20" cols="80">${applicationScope.talks}</textarea>
            </td>
        </tr>
    </table>
</body>

信息收集
index.jsp
<body>
    <table align="center">
            <tr>
                <td colspan="2">
                    <iframe src="chatinfo.jsp" width="800px" height="460px"></iframe>
                </td>
            </tr>
            <tr>
                <td align="center">
                    <form action="chat.do" method="post">
                        <input type="text" name="chat" size="60">
                        <input type="submit" value="发言">
                    </form>
                </td>
            </tr>
        </table>
</body>

前端搞定了，就要想想怎么写后面

由于不用数据库

发送的信息一定要保存在服务器端

根据其存在时间，我觉得用servletcontext来最好

写个监听器监听servletcontext

public class ContextListener implements ServletContextListener {
    public static final String Talks = "talks";
    //static final 静态最终啥的玩意 其实就是放在application里的数据
    //Talks是服务器内部调用的 ContextListener.Talks
    //talks是web前端调用的 applicationScope.talks
    private StringBuilder talks = new StringBuilder();
    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        // TODO Auto-generated method stub
        sce.getServletContext().removeAttribute(Talks);
    }

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        // TODO Auto-generated method stub
        sce.getServletContext().setAttribute(Talks, talks);
    }
}

最后上个servlet就好了

其中的dopost方法

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String talk=req.getParameter("talks");
        ServletContext sc = this.getServletContext();
        StringBuilder sb = (StringBuilder) sc
                .getAttribute(ContextListener.Talks);
        sb.append(String.format("说：%s%n", talk));
        resp.sendRedirect(req.getContextPath() + "/index.jsp");
    }

最后web.xml我就不写了