Servlet 参数

1.应用参数，在web.xml配置，所有Servlet共用

       <context-param>
		<param-name>driver</param-name>
		<param-value>com.mysql.jdbc.Driver</param-value>
	</context-param>

服务端获取配置的数据，实现Servlet接口

@Override
public void init(ServletConfig servletConfig) throws ServletException {
    //获取 ServletContext 对象
    ServletContext servletContext = servletConfig.getServletContext();
    //获取web全局的指定参数配置
    String driver = servletContext.getInitParameter("driver");
    System.out.println("driver:" + driver);
   //获取web全局全部的参数配置
   Enumeration<String> names = servletContext.getInitParameterNames();
	while(names.hasMoreElements()){
		 	String name = names.nextElement();
		 	System.out.println("-->" + name); 
	}
}

2.私有参数，在web.xml配置

      <servlet> 
        <servlet-name>helloServlet</servlet-name> 
        <servlet-class>com.demo.init.HelloServlet</servlet-class>
        <!-- 配置 Serlvet 的初始化参数 -->
        <init-param>
            <!-- 参数名 -->
            <param-name>user</param-name>
            <!-- 参数值 -->
            <param-value>root</param-value>
        </init-param>
         
    </servlet>

服务端获取参数数据，实现Servlet接口

    @Override
    public void init(ServletConfig servletConfig) throws ServletException { 
        //获取Servlet里的参数
        String user = servletConfig.getInitParameter("user");
        System.out.println("user： " + user); 
        //获取全部的servlet参数
        Enumeration<String> names =servletConfig.getInitParameterNames();
        while(names.hasMoreElements()){
            String name = names.nextElement();
            String value = servletConfig.getInitParameter(name);
            System.out.println(name + ": " + value);
        }
      }

3."会话“参数

ClassA设置参数值

request.getSession().setAttribute("CHECK_CODE", randomCode.toString()); 

ClassB获取参数值

String sessionCode = (String)request.getSession().getAttribute("CHECK_CODE");

4.“行为”参数，在HTML、Jsp等前端页面编辑用户信息，提交服务端

<form action="regedit" method="post"> 
        user: <input type="text" name="user"/>
        password: <input type="password" name="password"/> 
        <br><br> 
        interesting: 
        <input type="checkbox" name="interesting" value="party"/>Party
        <input type="checkbox" name="interesting" value="shopping"/>Shopping
        <input type="checkbox" name="interesting" value="sport"/>Sport  
        <input type="submit" value="Submit"/> 
</form>

   服务端获取用户编辑的内容，实现Servlet接口

    @Override
    public void service(ServletRequest request, ServletResponse response)
            throws ServletException, IOException { 
        String user = request.getParameter("user");
        String password = request.getParameter("password"); 
        System.out.println(user + ", " + password);  
        String interesting = request.getParameter("interesting");
        System.out.println(interesting);  
        //多值
        String [] interestings = request.getParameterValues("interesting");
        for(String interest: interestings){
            System.out.println("-->" + interest);
        }
        //获取全部参数键值
        Enumeration<String> names = request.getParameterNames();
        while(names.hasMoreElements()){
            String name = names.nextElement();
            String val = request.getParameter(name); 
        }
        }