初级登录案例

User.java

public class User {
	private int id;
	private String username;
	private String password;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}


}

LoginServlet.java

import java.io.IOException;

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

import com.xin.domain.User;
import com.xin.service.UserService;

/**
 * 提交表单时相应此servlet
 */
public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;


	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//设置编码
		response.setContentType("text/html;charset=utf-8");
		//接收用户名和密码
		String username=request.getParameter("username");
		String password=request.getParameter("password");
		//调用userservice里的login
		User user=new UserService().login(username,password);
		//判断user是否为空
		if(user==null){
			response.getWriter().print("用户名和密码不匹配");
		}else{
			response.getWriter().print(user.getUsername()+"欢迎回来");
		}
	}


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

}

UserService.java

import com.xin.dao.UserDao;
import com.xin.domain.User;

public class UserService {
	public User login(String username,String password){
		//调用dao
		UserDao dao=new UserDao();
		return dao.getUserByUsernameAndPwd(username,password);
	}
}

UserDao.java

import java.sql.SQLException;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;

import com.xin.domain.User;
import com.xin.utils.DataSourceUtils;

public class UserDao {
	public User getUserByUsernameAndPwd(String username,String password){
		//创建queryrunner
		QueryRunner qr=new QueryRunner(DataSourceUtils.getDataSource());
		String sql="select * from user where username=? and password=?";
		User user=null;
		//执行sql
		try {
			user=qr.query(sql, new BeanHandler<>(User.class),username,password);
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return user;
	}
}