在优化篇中还有什么问题##
- 阶段复习之jdbc连接数据库（三）——优化篇https://blog.csdn.net/IManiy/article/details/82382165
- jdbDriver等常量写死在java代码中，编译后无法修改
- 没有写全面，如查询多条数据、数据总条数等
本文详细介绍最终版本jdbc连接数据库#
数据库文件
CREATE TABLE `user` (
`userId` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(20) DEFAULT NULL,
`password` varchar(100) DEFAULT NULL,
`sex` int(1) DEFAULT '1' COMMENT '1表示男，0表示女',
`flag` int(1) DEFAULT '1' COMMENT '1表示正常，0表示不正常',
PRIMARY KEY (`userId`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
实体类
public class User {
private int userId;
private String username;
private String password;
private int sex;
private int flag;
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
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 int getSex() {
return sex;
}
public void setSex(int sex) {
this.sex = sex;
}
public int getFlag() {
return flag;
}
public void setFlag(int flag) {
this.flag = flag;
}
@Override
public String toString() {
return "User{" +
"userId=" + userId +
", username='" + username + '\'' +
", password='" + password + '\'' +
", sex=" + sex +
", flag=" + flag +
'}';
}
}
jdbc.properties
jdbDriver=com.mysql.jdbc.Driver
jdbcURL=jdbc:mysql://localhost:3306/jdbctest?characterEncoding=utf-8
jdbcUser=root
jdbcPassword=123456
工具类 DBConnectionUtil
public class DBConnectionUtil {
private static String jdbcDriver= "";
private static String jdbcURL="";
private static String jdbcUser="";
private static String jdbcPassword="";
//静态初始化块只会在类加载的时候执行一次
static {
//读取jdbc.properties文件
InputStream is=DBConnectionUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
Properties p=new Properties();
try {
p.load(is);
jdbcDriver =p.getProperty("jdbDriver");
jdbcURL=p.getProperty("jdbcURL");
jdbcUser=p.getProperty("jdbcUser");
jdbcPassword=p.getProperty("jdbcPassword");
} catch (IOException e) {
e.printStackTrace();
}
}
//创建
public static Connection CreateConnection(){
//获取连接
Connection conn=null;
//产生执行sql语句的对象
PreparedStatement ps=null;
//加载驱动
try {
Class.forName(jdbcDriver);
conn= DriverManager.getConnection(jdbcURL,jdbcUser,jdbcPassword);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
//关闭
public static void closeAll(ResultSet rs,PreparedStatement ps,Connection conn){
//关闭资源，先产生的后关闭
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
if(ps !=null){
try {
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}finally {
if (conn !=null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
}
}
}
dao层 Userdao
public class UserDao {
//保存user
public boolean saveUser(User user) {
boolean flag = false;
Connection conn = null;
PreparedStatement ps = null;
try {
conn = DBConnectionUtil.CreateConnection();
String sql = "INSERT INTO user (username,password) VALUES (?,?)";
ps = conn.prepareStatement(sql);
ps.setString(1, user.getUsername());
ps.setString(2, user.getPassword());
int rows = ps.executeUpdate();
if (rows > 0) {
flag = true;
System.out.println("插入数据成功！");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBConnectionUtil.closeAll(null, ps, conn);
}
return flag;
}
//通过id查询user
public User selectUserByUserId(int userId) {
User user = null;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = DBConnectionUtil.CreateConnection();
String sql = "SELECT * FROM user WHERE userId=?";
ps = conn.prepareStatement(sql);
ps.setInt(1, userId);
rs = ps.executeQuery();
if (rs.next()) {
user = new User();
user.setUserId(rs.getInt("userId"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setSex(rs.getInt("sex"));
user.setFlag(rs.getInt("flag"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBConnectionUtil.closeAll(rs, ps, conn);
}
return user;
}
//查询所有user
public List getAllUserList(){
List userList =new ArrayList();
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null;
try {
conn=DBConnectionUtil.CreateConnection();
String sql="select * from user";
ps=conn.prepareStatement(sql);
rs =ps.executeQuery();
while (rs.next()){
User user=new User();
user.setUserId(rs.getInt("userId"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setSex(rs.getInt("sex"));
user.setFlag(rs.getInt("flag"));
userList.add(user);
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
DBConnectionUtil.closeAll(rs,ps,conn);
}
return userList;
}
//获取总条数
public int getAllUserCount() {
int count = 0;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
conn = DBConnectionUtil.CreateConnection();
String sql = "select COUNT(*) 数量 from user";//取别名
try {
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
if (rs.next()) {
count = rs.getInt("数量");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBConnectionUtil.closeAll(rs, ps, conn);
}
return count;
}
//通过id删除user
public boolean deleteByUserId(int userId) {
boolean flag = false;
//获取连接
Connection conn = null;
//产生执行sql语句的对象
PreparedStatement ps = null;
//加载驱动
try {
conn = DBConnectionUtil.CreateConnection();
System.out.println(conn);
//删除一条记录
String sql="DELETE from `user` where userId=?";
ps = conn.prepareStatement(sql);
//参数赋值
ps.setInt(1,userId);
int rows = ps.executeUpdate();
if (rows > 0) {
flag=true;
System.out.println("删除数据成功！");
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
//关闭资源，先产生的后关闭
DBConnectionUtil.closeAll(null,ps,conn);
}
return true;
}
//通过id修改password
public boolean updateUser(User user){
boolean flag = false;
Connection conn =null;
PreparedStatement ps = null;
try {
conn = DBConnectionUtil.CreateConnection();
String sql ="update user set password =? where userId=?";
ps=conn.prepareStatement(sql);
ps.setString(1,user.getPassword());
ps.setInt(2,user.getUserId());
int rows = ps.executeUpdate();
if (rows > 0) {
flag=true;
System.out.println("修改数据成功！");
}
} catch (SQLException e) {
e.printStackTrace();
}
finally {
DBConnectionUtil.closeAll(null,ps,conn);
}
return flag;
}
}
进行测试
public class Test {
public static void main(String[] args) {
//查询
UserDao userDao=new UserDao();
System.out.println(userDao.selectUserByUserId(6));
//添加
User user=new User();
user.setUsername("cool");
user.setPassword("123456");
userDao.saveUser(user);
//删除
userDao.deleteByUserId(7);
//通过id修改password
User user2=new User();
user2.setUserId(8);
user2.setPassword("12345678");
userDao.updateUser(user2);
System.out.println(userDao.getAllUserCount());
}
}
