- HttpServlet：针对Http协议定义的一个Servlet基类，唯一的功能就是强制类型转换ServletRequest转换成HttpServletRequest，ServletResponse转换成HttpServletResponse，HttpServlet继承自GenericServlet，而GenericServlet实现了Servlet接口和ServletConfig接口。也就是说编写Servlet类不需要直接实现Servlet类，去继承HttpServlet就行。
- 好处：
- 不会产生多余无用的代码
- 不用在强制类型转换了（为了获取请求的方式是get还是post需要用到需要用request.getMethod()，其中request必须是HttpServletRequest类型的，HttpServlet在service(ServletRequest req, ServletResponse res)已经强制类型转换好了）
- 在service(HttpServletRequest req, HttpServletResponse resp)重载方法中获取请求方式，get请求会调用doget方法，post请求会执行dopost方法。所以我们可以再这2个方法中定义我们自己的业务逻辑
3 . Http中的方法：
HttpServlet()
doGet(HttpServletRequest, HttpServletResponse)
getLastModified(HttpServletRequest)
doHead(HttpServletRequest, HttpServletResponse)
doPost(HttpServletRequest, HttpServletResponse)
doPut(HttpServletRequest, HttpServletResponse)
doDelete(HttpServletRequest, HttpServletResponse)
getAllDeclaredMethods(Class< ? >)
doOptions(HttpServletRequest, HttpServletResponse)
doTrace(HttpServletRequest, HttpServletResponse)
service(HttpServletRequest, HttpServletResponse)
maybeSetLastModified(HttpServletResponse, long)
service(ServletRequest, ServletResponse)
改进后的实例:
HttpServlet
/**
* 针对Http协议定义的一个Servlet基类
*唯一的功能就是强制类型转换ServletRequest转换成HttpServletRequest，ServletResponse转换成
*HttpServletResponse
*/
public class MyHttpServlet extends MyGenericServlet {
@Override
public void service(ServletRequest arg0, ServletResponse arg1)
throws ServletException, IOException {
if(arg0 instanceof HttpServletRequest){
HttpServletRequest httpServletRequest = (HttpServletRequest) arg0;
if(arg1 instanceof HttpServletResponse){
HttpServletResponse httpServletResponse = (HttpServletResponse) arg1;
service(httpServletRequest, httpServletResponse);
}
}
}
public void service(HttpServletRequest arg0, HttpServletResponse arg1)
throws ServletException, IOException {
//1.获取请求方式
String method = arg0.getMethod();
//2.根据请求的方式再调用对应的处理方法
if("GET".equalsIgnoreCase(method)){
doGet(arg0, arg1);
}else if("POST".equalsIgnoreCase(method)){
doPost(arg0, arg1);
}
}
public void doPost(HttpServletRequest arg0, HttpServletResponse arg1)
throws ServletException, IOException{
}
public void doGet(HttpServletRequest arg0, HttpServletResponse arg1)
throws ServletException, IOException{
}
}
Servlet：
public class LoginServlet3 extends MyHttpServlet {
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//获取请求的方式
String method = request.getMethod();
System.out.println("请求方式：" + method);
//1.获取请求参数username，password（获取的是表单信息）
String username = request.getParameter("username");
String password = request.getParameter("password");
//2.获取当前web应用的初始化参数user，password。
String initUser = getServletContext().getInitParameter("user");
String initPassword = getServletContext().getInitParameter("password");
PrintWriter out = response.getWriter();
//3.比对
if(initUser.equals(username) && initPassword.equals(password)){
//4.打印响应字符串
out.println("Hello: " + username);
}else{
out.println("Sorry: " + username);
}
}
@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//获取请求的方式
HttpServletRequest httpServletRequest = (HttpServletRequest) request;
String method = httpServletRequest.getMethod();
System.out.println("请求方式：" + method);
//1.获取请求参数username，password（获取的是表单信息）
String username = request.getParameter("username");
String password = request.getParameter("password");
//2.获取当前web应用的初始化参数user，password。
String initUser = getServletContext().getInitParameter("user");
String initPassword = getServletContext().getInitParameter("password");
PrintWriter out = response.getWriter();
//3.比对
if(initUser.equals(username) && initPassword.equals(password)){
//4.打印响应字符串
out.println("Hello: " + username);
}else{
out.println("Sorry: " + username);
}
}
}
页面：
<body>
<form action="loginServlet" method="get">
user：<input type="text" name="user"/>
<br>
password：<input type="password" name="password"/>
<br>
interesting：
<input type="checkbox" name="interesting" value="read"/>read
<input type="checkbox" name="interesting" value="walk"/>walk
<input type="checkbox" name="interesting" value="swing"/>swing
<input type="checkbox" name="interesting" value="shopping"/>shopping
<input type="checkbox" name="interesting" value="tv"/>TV
<br>
<input type="submit" value="Submit"/>
</form>
</body>