servlet的三种开发方法：
*************************
1(import java.servlet.*;******************************
public class Hello implements Servlet {
/*销毁Servlet实例（释放内存）,调用它的三种情况：1，reload 该Servlet(webApp)
* 2,关闭tomcat，3，关机
*/
public void destroy() {
System.out.println(
"destroy it");
}
public ServletConfig getServletConfig() {
// TODO Auto-generated method stub
return null;
}
public String getServletInfo() {
// TODO Auto-generated method stub
return null;
}
/*
该函数用户初始化Servlet，类似于java中类的构造函数，只会被调用一次（当用户第一次访问该Servlet
的时候被调用
*/
public void init(ServletConfig arg0) throws ServletException {
// TODO Auto-generated method stub
System.
out.println(
"init");
}
/*这个函数用户处理业务逻辑，程序员把业务逻辑代码写在这里
* 当用户访问一次该Servlet的时候都会被调用
req用于获得客户端（浏览器）的信息，而res则相反，向客户端（浏览器）返回信息
*/
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
System.out.println(
" service it");
//从res中得到Printwriter
PrintWriter pw=
res.getWriter();
pw.println("hello,world");
}
}
********************************************
2（import java.servlet.GenericServlet.*)****************
只需重写GenericServlet的service方法
public class test_GenericServlet extends GenericServlet{
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
try{
PrintWriter pw=
res.getWriter();
pw.println("hello,world,这是利用service");
}
catch(Exception ex){
ex.printStackTrace();
}
}
}
*************
3，HttpServlet***************
import javac.service.http.*
;
[import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;]
public class test_httpServlet extends HttpServlet {
/*处理get请求，resquest:用户获得客户端（浏览器）的请求
* response：用户向客户端（浏览器）返回信息*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//业务逻辑，也可以和doPost的使用调过来
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}
