Servlet 參數

1.應用參數，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>

服務端獲取配置的數據，實現Servlet介面

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

2.私有參數，在web.xml配置

      <servlet> 
        <servlet-name>helloServlet</servlet-name> 
        <servlet-class>com.demo.init.HelloServlet</servlet-class>
        <!-- 配置 Serlvet 的初始化參數 -->
        <init-param>
            <!-- 參數名 -->
            <param-name>user</param-name>
            <!-- 參數值 -->
            <param-value>root</param-value>
        </init-param>
         
    </servlet>

服務端獲取參數數據，實現Servlet介面

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

3."會話“參數

ClassA設置參數值

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

ClassB獲取參數值

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

4.“行為”參數，在HTML、Jsp等前端頁面編輯用戶信息，提交服務端

<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>

   服務端獲取用戶編輯的內容，實現Servlet介面

    @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);
        }
        //獲取全部參數鍵值
        Enumeration<String> names = request.getParameterNames();
        while(names.hasMoreElements()){
            String name = names.nextElement();
            String val = request.getParameter(name); 
        }
        }