操作数据库，拼接SQL语句，执行SQL语句
/**
* 操作数据库步骤
* 3.1导入操作数据库的jar
* 3.2数据库驱动
* 3.3创建连接对象
* 3.4定义SQL语句
* 3.5创建执行SQL语句的对象
* 3.6执行SQL语句
* 3.7处理执行SQL语句结果
* 3.8关闭数据库,释放资源
*
*/
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet({ "/LoginServlet", "/login.do" })
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
/**
* 登录功能
*
* 1.获得用户名及密码。
* 2.数据有效性验证,验证失败的话，返回登录页面告诉用户。
* 3.操作数据库，拼接SQL语句，执行SQL语句。
* 4.查询成功，进入登录成功页面。
* 5.查询不成功，返回登录页面。
*
*/
//设置响应的类型
response.setContentType("text/html; charset=UTF-8");
//设置request编码
request.setCharacterEncoding("UTF-8");
//1.获得用户名及密码
//取得用户名
String username = request.getParameter("username");
//取得密码
String userpass = request.getParameter("userpass");
System.out.println("username:"+username+" userpass:"+userpass);
//2.数据有效性验证,验证失败的话，返回登录页面告诉用户
//错误集合
ArrayList<String> list = new ArrayList<String>();
//验证用户名
if(username==null || "".equals(username)) {
list.add("1");
}
//验证密码
if(userpass==null || "".equals(userpass)) {
list.add("2");
}
//判断验证是否通过，不通过返回登录页面
if(list.size()>0) {
//请求转发
request.setAttribute("listinfo", list);
request.getRequestDispatcher("login.jsp").forward(request, response);
return;
}
//3.操作数据库，拼接SQL语句，执行SQL语句
/**
* 操作数据库步骤
* 3.1导入操作数据库的jar
* 3.2数据库驱动
* 3.3创建连接对象
* 3.4定义SQL语句
* 3.5创建执行SQL语句的对象
* 3.6执行SQL语句
* 3.7处理执行SQL语句结果
* 3.8关闭数据库,释放资源
*
*/
//3.1导入操作数据库的jar
Connection conn = null;
PreparedStatement psts = null;
ResultSet rs = null;
try {
//3.2数据库驱动
Class.forName("com.mysql.jdbc.Driver");
//3.3创建连接对象
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/expressdata", "root", "root");
//3.4定义SQL语句
String sql = "SELECT * FROM userinfo WHERE username=? AND userpass=?";
//3.5创建执行SQL语句的对象
psts = conn.prepareStatement(sql);
psts.setString(1, username);
psts.setString(2, userpass);
//3.6执行SQL语句
rs= psts.executeQuery();
//3.7处理执行SQL语句结果
if(rs.next()) {
//登录成功状态保留下来
request.getSession().setAttribute("loginuser", username);
//跳转到登录成功页面
response.sendRedirect("index.jsp");
}
else {
//登录失败,返回到登录页面
list.add("3");
request.setAttribute("listinfo", list);
request.getRequestDispatcher("login.jsp").forward(request, response);
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally {
//3.8关闭数据库,释放资源
try {
if(rs!=null)
rs.close();
if(psts!=null)
psts.close();
if(conn!=null)
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}