笔记如下
-
设计规范
2018-02-23_115807.png - UserDao.java
public class UserDao {
//查询单个用户 ,这里是dao的核心类,封装了对数据的操作
public User selectOne(User user) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
//获得连接
conn = JdbcUtils.getConnection();
stmt = conn.createStatement();
String sql = "select * from users where username='"+user.getUsername()+"' and password='"+user.getPassword()+"'";
rs = stmt.executeQuery(sql);
User loginuser = null;
//解析结果集
if(rs.next()) {
loginuser = new User();
int id = rs.getInt("id");
String username = rs.getString("username");
String password = rs.getString("password");
String nickname = rs.getString("nickname");
//封装用户信息
loginuser.setId(id);
loginuser.setNickname(nickname);
loginuser.setPassword(password);
loginuser.setUsername(username);
}
return loginuser;
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}finally {
//释放资源
JdbcUtils.release(rs, stmt, conn);
}
return null;
}
//查询单个用户 ,这里是dao的核心类,封装了对数据的操作
public User selectOne2(User user) {
Connection conn = null;
ResultSet rs = null;
PreparedStatement stmt =null;
try {
//获得连接
conn = JdbcUtils.getConnection();
//String sql = "select * from users where username='"+user.getUsername()+"' and password='"+user.getPassword()+"'";
//使用?占位符,防止sql注入(黑客改变关键字,达到不可告人的目的)
String sql = "select * from users where username=? and password=?";
stmt = conn.prepareStatement(sql);
//替换占位符
stmt.setString(1, user.getUsername());
stmt.setString(2, user.getPassword());
//executeQuery()有个重载无参数,预编译后直接执行
//rs = stmt.executeQuery(sql);
rs = stmt.executeQuery();
User loginuser = null;
//解析结果集
if(rs.next()) {
loginuser = new User();
int id = rs.getInt("id");
String username = rs.getString("username");
String password = rs.getString("password");
String nickname = rs.getString("nickname");
//封装用户信息
loginuser.setId(id);
loginuser.setNickname(nickname);
loginuser.setPassword(password);
loginuser.setUsername(username);
}
return loginuser;
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}finally {
//释放资源
JdbcUtils.release(rs, stmt, conn);
}
return null;
}
}
- User.java
public class User {
private int id;
private String username;
private String password;
private String nickname;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
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;
}
public String getNickname() {
return nickname;
}
public void setNickname(String nickname) {
this.nickname = nickname;
}
}
- UserServlet.java
public class UserService {
public User login(User user) {
//调用dao核心类
UserDao udao = new UserDao();
return udao.selectOne2(user);
}
}
- JdbcUtils.java
/*
*
* 配置文件:
*
*/
public class JdbcUtils {
//使用ResouceBundle
private static String driverClass = null ;
private static String url = null ;
private static String username = null ;
private static String password = null ;
static {
//专门用于读取properties文件
//properties文件要放在src下
ResourceBundle bundle = ResourceBundle.getBundle("db");
driverClass = bundle.getString("driverClass");
url = bundle.getString("url");
username = bundle.getString("username");
password = bundle.getString("password");
}
public static Connection getConnection() {
try {
loadDriver();
//建立连接
return DriverManager.getConnection(url,username,password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
private static void loadDriver() {
try {
//这里是加载字节码.在Driver类中,
Class.forName(driverClass);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//释放资源
public static void release(ResultSet rs ,Statement stmt, Connection conn) {
if(rs != null) {
try {
//释放获得的资源
rs.close();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
//设置为空:斩断引用的对象
//有利于回收垃圾
rs = null;
}
if(stmt != null) {
try {
stmt.close();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
stmt = null;
}
if(conn != null) {
try {
conn.close();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
conn = null;
}
}
}
- LoginService.java
/*
*
* 处理用户登录请求的servlce
*/
@WebServlet("/login")
public class LoginServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获得用户名和密码
User user = new User();
try {
//使用BeanUtils封装javabean
BeanUtils.populate(user, request.getParameterMap());
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//调用业务层完成登录
UserService us = new UserService();
User loginUser = us.login(user);
if(loginUser == null) {
//说明登录失败,提示错误信息
request.setAttribute("message", "对不起,用户名或密码错误,不要瞎搞.....");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}else {
//登录成功,将登陆的用户存到session域中
request.getSession().setAttribute("loginUser", loginUser);
response.sendRedirect(request.getContextPath()+"/index.jsp");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
- .properties
url=jdbc\:mysql\:///day15_jdbc
username=root
password=123456
driverClass=com.mysql.jdbc.Driver