JavaWeb——操作MySQL数据库实现增删改查操作
接着完善此网页
https://blog.csdn.net/nine06/article/details/133355867?spm=1001.2014.3001.5501
https://blog.csdn.net/nine06/article/details/133355867?spm=1001.2014.3001.5501
实现增删改查功能
1、查询
1.1 查询所有用户
1.1.1、Dao层
/**
* 查询所有用户
*/
public List findUserAll(){
Connection connection = DBUtils.getConnection();
String sql = "select id,username,password,gender,hobby,address,remark from user";
PreparedStatement ps = null;
ResultSet rs = null;
ArrayList users = new ArrayList<>();
try {
ps = connection.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()){
User user = new User();
user.setId(rs.getInt(1));
user.setUsername(rs.getString(2));
user.setPassword(rs.getString(3));
user.setGender(rs.getString(4));
user.setHobby(rs.getString(5));
user.setAddress(rs.getString(6));
user.setRemark(rs.getString(7));
users.add(user);
}
} catch (SQLException e) {
e.printStackTrace();
}
DBUtils.closeDB(connection,ps,rs);
return users;
} 1.1.2、Service层
/**
*查询所有用户
**/
public List showAllUser(){
List users = new UserDao().findUserAll();
return users;
} 1.1.3、Controller层
/**
* 查询所有用户信息
*/
if ("showAllUser".equals(userAction)){
List users = new UserService().showAllUser();
if (users.isEmpty()){
req.setAttribute("infor","未查询到相关用户信息");
req.getRequestDispatcher("showalluser.jsp").forward(req,resp);
}else{
req.setAttribute("users",users);
req.getRequestDispatcher("showalluser.jsp").forward(req,resp);
}
} 1.1.4、效果
查询到的所有用户
1.2 通过ID查询用户
1.2.1、Dao层
/**
* 通过id查询用户
*/
public User findUserByID(Integer id){
Connection connection = DBUtils.getConnection();
String sql = "select id,username,password,gender,hobby,address,remark from user WHERE id = ?";
PreparedStatement ps = null;
ResultSet rs = null;
User user = null;
try {
ps = connection.prepareStatement(sql);
ps.setInt(1,id);
rs = ps.executeQuery();
while (rs.next()){
user = new User();
user.setId(rs.getInt(1));
user.setUsername(rs.getString(2));
user.setPassword(rs.getString(3));
user.setGender(rs.getString(4));
user.setHobby(rs.getString(5));
user.setAddress(rs.getString(6));
user.setRemark(rs.getString(7));
}
} catch (SQLException e) {
e.printStackTrace();
}
DBUtils.closeDB(connection,ps,rs);
return user;
}1.2.2、Service层
/**
* 通过ID查找用户(数据回显)
*/
public User showUserBack(Integer id){
return new UserDao().findUserByID(id);
}1.2.3、Controller层
/**
* 回显用户信息
*/
if ("showUserBack".equals(userAction)){
String id = req.getParameter("id");
//回显
UserService userService = new UserService();
User user = userService.showUserBack(Integer.parseInt(id));
req.setAttribute("user",user);
req.getRequestDispatcher("showuserback.jsp").forward(req,resp);
}1.2.4、效果
这里的通过id查询用户主要用在添加用户时让数据回显没办法直观看到效果，所以是在IDEA控制台输出的效果。
2、添加
2.1 添加用户
2.1.1、Dao层
/**
* 添加用户
*/
public int addUser(User user){
//连接数据库
Connection connection = DBUtils.getConnection();
String sql = "INSERT INTO USER(username,password,gender,hobby,address,remark) VALUE (?,?,?,?,?,?)";
PreparedStatement ps = null;
try {
ps = connection.prepareStatement(sql);
ps.setString(1,user.getUsername());
ps.setString(2,user.getPassword());
ps.setString(3,user.getGender());
ps.setString(4,user.getHobby());
ps.setString(5,user.getAddress());
ps.setString(6,user.getRemark());
int i = ps.executeUpdate();
return i;
} catch (SQLException e) {
e.printStackTrace();
}
DBUtils.closeDB(connection,ps,null);
return 0;
}2.1.2、Service层
/**
* 添加用户
**/
public int register(User user){
UserDao userDao = new UserDao();
boolean flag = userDao.findUserByName(user.getUsername());
int state = 0;
if (flag){
state = 2;
}else {
int i = userDao.addUser(user);
if (i > 0){
state = 1;
}else {
state = 0;
}
}
return state;
}2.1.3、Controller层
/**
* 添加用户
**/
if ("register".equals(userAction)){
User user = new User();
try {
BeanUtils.populate(user,req.getParameterMap());
user.setHobby(ArrayToString.arraytostring(req.getParameterValues("hobby")));
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
//验证数据
Map error = ValidateDemo.validateUser(user);
if (error.isEmpty()){
UserService userService = new UserService();
int register = userService.register(user);
if (register == 0){
resp.sendRedirect("/servlet/registerfail.jsp");
}
if (register == 1){
resp.sendRedirect("/servlet/refresh.jsp");
}
if (register == 2){
resp.sendRedirect("/servlet/register.jsp?registerfail="+URLEncoder.encode("该用户已存在!","utf-8"));
}
}else{
req.setAttribute("error",error);
req.getRequestDispatcher("register.jsp").forward(req,resp);
}
} 2.1.4、效果
3、修改
3.1 修改用户
3.1.1、Dao层
/**
* 修改用户信息
*/
public int updateUser(User user){
Connection connection = null;
String sql = null;
PreparedStatement ps = null;
int i = 0;
try {
connection = DBUtils.getConnection();
sql = "UPDATE USER SET username=?,password=?,gender=?,hobby=?,address=?,remark=? where id = ?";
ps = connection.prepareStatement(sql);
ps.setString(1,user.getUsername());
ps.setString(2,user.getPassword());
ps.setString(3,user.getGender());
ps.setString(4,user.getHobby());
ps.setString(5,user.getAddress());
ps.setString(6,user.getRemark());
ps.setInt(7,user.getId());
i = ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
DBUtils.closeDB(connection,ps,null);
return i;
}3.1.2、Service层
/**
* 用户修改
*/
public boolean modifyUser(User user){
int i = new UserDao().updateUser(user);
if (i > 0){
return true;
}else {
return false;
}
}3.1.3、Controller层
/**
* 修改用户信息
*/
if ("modifyUser".equals(userAction)){
User user = new User();
try {
BeanUtils.populate(user,req.getParameterMap());
boolean flag = new UserService().modifyUser(user);
if (flag){
List users = new UserService().showAllUser();
if (users.isEmpty()){
req.setAttribute("infor","未查询到相关用户信息");
req.getRequestDispatcher("showalluser.jsp").forward(req,resp);
}else{
req.setAttribute("users",users);
req.getRequestDispatcher("showalluser.jsp").forward(req,resp);
}
}else {
resp.getWriter().print("修改失败");
}
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
} 3.1.4、效果
修改了地址
4、删除
4.1 删除用户
4.1.1、Dao层
/**
* 删除用户信息
*/
public int deleteUserByID(Integer id){
Connection connection = DBUtils.getConnection();
String sql = "DELETE FROM USER WHERE id = ?";
PreparedStatement ps = null;
int i = 0;
try {
ps = connection.prepareStatement(sql);
ps.setInt(1,id);
i = ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
DBUtils.closeDB(connection,ps,null);
return i;
}4.1.2、Service层
/**
* 删除用户
*/
public boolean deleteUser(Integer id){
int i = new UserDao().deleteUserByID(id);
if (i > 0){
return true;
}else {
return false;
}
}4.1.3、Controller
/**
* 删除用户
*/
if ("deleteUser".equals(userAction)){
String id = req.getParameter("id");
UserService userService = new UserService();
boolean flag = userService.deleteUser(Integer.parseInt(id));
if (flag){
List users = new UserService().showAllUser();
if (users.isEmpty()){
req.setAttribute("infor","未查询到相关用户信息");
req.getRequestDispatcher("showalluser.jsp").forward(req,resp);
}else{
req.setAttribute("users",users);
req.getRequestDispatcher("showalluser.jsp").forward(req,resp);
}
}else {
resp.getWriter().print("删除失败");
}
} 4.1.4、效果
把id为12的删除
这就是增删改查部分。