• 动手学servlet(二) servlet基础


    1、我们来试着向一个servlet提交一个表单,现在webcontent下新建一个login.html页面,其中action对应servelt类名,代码如下:

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8">
    <title>提交表单</title>
    </head>
    <body>
    <form action="LoginServlet" method="post">
    用户名:<input name="username" type="text"><br>
    密码:<input name="password" type="password"><br>
    <input value="提交" name="submit" type="submit">
    </form>
    </body>
    </html>
    代码

        附:request.getParameter("username");可以读取用户名输入框的值,针对复选框需要调用request.getParameterValues(name);将返回一个字符串数组

    2、新建一个servlet类LoginServlet,代码如下:

    package servletdemo;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /**
     * Servlet implementation class LoginServlet
     */
    @WebServlet("/LoginServlet")
    public class LoginServlet extends HttpServlet {
        private static final long serialVersionUID = 1L;
           
        /**
         * @see HttpServlet#HttpServlet()
         */
        public LoginServlet() {
            System.out.print("loginservlet...");
            // TODO Auto-generated constructor stub
        }
    
        @Override
        public void init() throws ServletException {
            // TODO 自动生成的方法存根        
            System.out.print("init...");
        }
        /**
         * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
         */
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            System.out.print("doget...");
        }
    
        /**
         * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
         */
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            System.out.print("dopost...");
        }
        
        @Override
        public void destroy() {
            // TODO 自动生成的方法存根
            System.out.print("destory...");
        }
    
    }
    代码

         注意:右键新建一个servlet不会在web.xml生成对应的配置标签,是因为servlet类里已经有了@WebServlet注解

    3、运行login.html,可以验证servlet的生命周期,效果如下:

    4、有时候需要获得web.xml里一些配置信息,例如下面的配置,其中name相当于key,value就是对应的值

    <context-param>
    <param-name>henry</param-name>
    <param-value>123</param-value>
    </context-param>

    用这行代码就可以获得KEY对应的值:String result=this.getServletContext().getInitParameter("henry");  

    5、servlet在MVC中相当于controller,所以经常需要做一些页面的跳转,下面来看看页面导航的实现

    • 请求重定向

        直接跳转到其他的网站,response.sendRedirect("http://www.baidu.com");

    • 请求包含

        就是跳转到另外一个serlvet,但是也输出本servlet的内容,具体看例子

    //需要跳转的servlet的doGet()方法
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            PrintWriter out=response.getWriter();
            out.print("<h1>LoginServlet</h1>");
            request.getRequestDispatcher("MyServlet").include(request, response);
        }
    
    
    //跳转到的MyServlet的doGet()方法
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            // TODO 自动生成的方法存根
            String result=this.getServletContext().getInitParameter("henry");
            System.out.print(result);
            resp.setContentType("text/html;charset=gbk");
            PrintWriter pw=resp.getWriter();
            pw.write(result);
            pw.close();
        }
    代码

    • 请求跳转

         也是跳转到另外一个servlet,但是不输出本servlet的内容

    //需要跳转的servlet的doGet()方法
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            PrintWriter out=response.getWriter();
            out.print("<h1>LoginServlet</h1>");
            request.getRequestDispatcher("MyServlet").forward(request, response);
        }
    
    
    //跳转到的MyServlet的doGet()方法
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            // TODO 自动生成的方法存根
            String result=this.getServletContext().getInitParameter("henry");
            System.out.print(result);
            resp.setContentType("text/html;charset=gbk");
            PrintWriter pw=resp.getWriter();
            pw.write(result);
            pw.close();
        }
    代码

         注意:getRequestDispatcher()方法的参数不是servlet类名,而是web.xml里url-pattern节点中的值

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  • 原文地址:https://www.cnblogs.com/SamFlynn/p/4478166.html
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