servlet基础项

1.使用doGet和doPost简便的建一个servlet：

创一个web类 extends HttpServlet;

后分别输入doGet和doPost使用快捷键alt+/火速输出，

然后定义两条获取：

String username = request.getParameter("username");

String password = request.getParameter("password");

之后可以用sysout输出语句运行测试，格式：网址后+ ？ + username + = + string型

例子：

package com.yy.get;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Ser extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
System.out.println(username);
System.out.println(password);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
System.out.println(username);
System.out.println(password);

}

}

网址内容：http://pc-201703*****x:8080/new008/Ser?username=baibai

2.请求转发，服务器内部转发：request.getRequestDispatcher("/chenggong.jsp").forward(request, response);

例子：

package com.yy.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.yy.servlet.UserDao;
import com.yy.servlet.User;


public class Firstser extends HttpServlet {

//20170705学习，使用doGet与doPost编写servlet

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");

//调用map验证
Map<String, String> map = new HashMap<String, String>();
map.put("username", username);
map.put("password", password);
User user = UserDao.getInstance().getUserByMap(map);


//请求转发，服务器内部转发
if(user != null){
request.setAttribute("username", username);
request.getRequestDispatcher("/chenggong.jsp").forward(request, response);
return;
}else{
request.setAttribute("username", username);
request.getRequestDispatcher("/shibai.jsp").forward(request, response);
return;
}

}
}

3.请求定向：

response.sendRedirect("/new009/shibai.jsp");

return;

例子：

package com.yy.servletres;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servleta extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doPost(request, response);
}

//请求重定向
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.sendRedirect("/new009/shibai.jsp");
return;
}

}