（1）ServletContext作用域

可以寫一個SetAttributeServlet檔案與GetAttributeServlet

程式碼如下：

@WebServlet("/MyFirstServlet")
public class SetAttributeServlet extends HttpServlet {


protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  
 //在ServletContext中儲存一個資訊
ServletContext servletContext=getServletContext();
//新增String型別到servletContext的作用域中
//第一種方式
servletContext.setAttribute("name", "zhangsan");
servletContext.setAttribute("sex", "nan");
//第二種方式，新增物件
servletContext.setAttribute("user", new User("wangwu","231"));
//移除,寫上這行程式碼後就會移除掉這個物件
//servletContext.removeAttribute("User");
//第三種方式，新增集合
        ArrayList<User> arrayList=new ArrayList<User>();
        arrayList.add(new User("zhaoxin","1234"));
        arrayList.add(new User("liubei","123435"));
       
        servletContext.setAttribute("userList", arrayList);



}
         /**
          * 處理post請求
          */

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//呼叫doGet
doGet(request, response);

}
}

GetAttributeServlet中的程式碼：

public class GetAttributeServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

super.doPost(req, resp);
}
                 

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 
//獲取servletContext的物件
ServletContext servletContext=getServletContext();
//獲取普通引數
String name=(String)servletContext.getAttribute("name");
String sex=(String)servletContext.getAttribute("sex");
System.out.println(name+"---"+sex);
//獲取物件
User user=(User)servletContext.getAttribute("user");
System.out.println(user.toString());//轉換成string型別
//獲取集合
ArrayList<User> userList=(ArrayList<User>)servletContext.getAttribute("userList");
for(User user2: userList) {
 
System.out.println(user2.toString());
}


}
}

（2）獲取請求引數的幾種方式

在RequestServlet.java中程式碼：

/**
 * Servlet implementation class RequestServlet
 */
@WebServlet("/RequestServlet")
public class RequestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
       
   
    public RequestServlet() {
        super();
        // TODO Auto-generated constructor stub
    }


protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 //獲取請求頭資訊
Enumeration<String> headerNames = request.getHeaderNames();
while(headerNames.hasMoreElements()) {
 String key=headerNames.nextElement();
 //請求頭的資訊
 String value=request.getHeader(key);
 System.out.println(key+"-----"+value);

}

/**
* 獲取請求方法
*/
String method=request.getMethod();
System.out.println(method);
/**
* 獲取具體單個請求引數
*/
String username=request.getParameter("username");
String password=request.getParameter("password");
System.out.println(username+"----"+password);

}


/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

doGet(request, response);
}

}

在login.html中的程式碼樣式如下：action中表明在提交表單時會跳轉到RequestServlet頁面，在這裡的提交方法是get方法

執行結果：

點選登入後，會在後臺console中顯示出使用者名稱與密碼。

如下的HTML在點選註冊時也會電泳RequestServlet檔案，

我們也可以在RequestServlet中寫程式碼來獲取資訊

/**
 * Servlet implementation class RequestServlet
 */
@WebServlet("/RequestServlet")
public class RequestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
       
   
    public RequestServlet() {
        super();
        // TODO Auto-generated constructor stub
    }


protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 //獲取請求頭資訊
Enumeration<String> headerNames = request.getHeaderNames();
while(headerNames.hasMoreElements()) {
 String key=headerNames.nextElement();
 //請求頭的資訊
 String value=request.getHeader(key);
 System.out.println(key+"-----"+value);

}

/**
* 獲取請求方法
*/
String method=request.getMethod();
System.out.println(method);
/**
* 獲取請求引數
*/
String username=request.getParameter("username");
String password=request.getParameter("password");
System.out.println(username+"----"+password);

/**
* 在form.html中的愛好有多個，所以用陣列
*/

String[] hobbys=request.getParameterValues("hobbys");
for(String h:hobbys) {
System.out.println(h);

}
//獲取引數的map集合
Map<String,String[]> parameterMap=request.getParameterMap();
//獲取到的是鍵值對的關係，因為一個鍵可能對應多個值
Set<Entry<String,String[]>> entrySet=parameterMap.entrySet();
for(Entry<String,String[]> entry:entrySet) {
String key=entry.getKey();
String[] value=entry.getValue();
for(String v: value) {
 System.out.println(key+"---"+value);
 
}

}

}


/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

doGet(request, response);
}


}