⭐简单说两句⭐
作者：后端小知识
个人主页：后端小知识
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文章目录
- JDBC
- JDBC访问数据库步骤
- 模拟登录
- 事务
JDBC
内容和代码为在校期间做实验写的，初学者可以参考参考，其中也有很多写法不规范，但是入门还是可以，后面看情况可以出一篇详细的学习JDBC的文章
JDBC访问数据库步骤
• 1：加载一个Driver驱动
• 2：创建数据库连接（Connection）
• 3 ：创建SQL命令发送器Statement
• 4：通过Statement发送SQL命令并得到结果
• 5：处理结果（select语句）
• 6：关闭数据库资源
• ResultSet
• Statement
• Connection
public class TestInsert {
public static void main(String[] args) throws Exception{
String driver = "com.mysql.cj.jdbc.Driver";
String url="jdbc:mysql://127.0.0.1:3306/shiyan?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
String user="root";
String pasaword="tcx119";
//加载驱动
Class.forName (driver);
//和数据库建立连接
Connection conn = DriverManager.getConnection (url,user,pasaword);
// System.out.println (conn);
//创建sql命令发射器
Statement smt = conn.createStatement ();
//准备sql命令
String sql = "insert into score values(12345666,'X6666',90.2,85.3)";
//处理结果
int n = smt.executeUpdate (sql);
if(n>0){
System.out.println ("插入成功");
}else{
System.out.println ("插入失败");
}
//关闭资源
smt.close ();
conn.close ();
}
}查询的结果
code
//这是Emp的代码
public class Emp {
private String teacherno;
private String tname;
private String major;
private String prof;
private String department;
public Emp() {
}
public Emp(String teacherno, String tname, String major, String prof, String department) {
this.teacherno = teacherno;
this.tname = tname;
this.major = major;
this.prof = prof;
this.department = department;
}
public String getTeacherno() {
return teacherno;
}
public void setTeacherno(String teacherno) {
this.teacherno = teacherno;
}
public String getTname() {
return tname;
}
public void setTname(String tname) {
this.tname = tname;
}
public String getMajor() {
return major;
}
public void setMajor(String major) {
this.major = major;
}
public String getProf() {
return prof;
}
public void setProf(String prof) {
this.prof = prof;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
@Override
public String toString() {
return "Emp{" +
"teacherno='" + teacherno + '\'' +
", tname='" + tname + '\'' +
", major='" + major + '\'' +
", prof='" + prof + '\'' +
", department='" + department + '\'' +
'}';
}
}//这才是主场
public class TestSelect {
public static void main(String[] args) throws SQLException {
List<Emp> list = selectAll ();
for (Emp emp:list){
System.out.println (emp.getTeacherno ()+"\t"+emp.getTname ()+
"\t"+emp.getMajor ()+"\t"+emp.getProf ()+"\t"+emp.getDepartment ());
}
}
//后台处理
public static List<Emp> selectAll() throws SQLException {
String driver = "com.mysql.cj.jdbc.Driver";
String url="jdbc:mysql://127.0.0.1:3306/shiyan?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
String user="root";
String password="tcx119";
Connection conn=null;
Statement stmt = null;
ResultSet rs=null;
Emp emp = null;
List<Emp> list =new ArrayList<Emp>();
try{
Class.forName (driver);
conn = DriverManager.getConnection (url,user,password);
stmt= conn.createStatement ();
String sql = " select * from teacher";
rs= stmt.executeQuery (sql);
while(rs.next ()){
String teacherno = rs.getString ("teacherno");
String tname = rs.getString ("tname");
String major = rs.getString ("major");
String prof = rs.getString ("prof");
String department = rs.getString ("department");
emp=new Emp (teacherno,tname,major,prof,department);
list.add (emp);
}
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace ();
} finally {
assert rs != null;
rs.close ();
stmt.close ();
conn.close ();
}
return list;
}
}模拟登录
public class Login {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
//前台
Scanner sc = new Scanner (System.in);
System.out.println ("请输入用户名");
String userId = sc.next ();
System.out.println ("请输入密码");
String inputPassword = sc.next ();
User user = testLogin (userId,inputPassword);
if (user==null){
System.out.println ("登录失败,请检查用户名或密码是否正确");
}else{
System.out.println ("登录成功： 姓名： "+user.getRealName ());
}
}
// 后台
public static User testLogin(String userId,String inputPassword) throws ClassNotFoundException, SQLException {
String driver = "com.mysql.cj.jdbc.Driver";
String url="jdbc:mysql://127.0.0.1:3306/shiyan?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
String user="root";
String pasaword="tcx119";
Class.forName (driver);
User user2=null;
Connection conn = DriverManager.getConnection (url,user,pasaword);
String sql = "select * from t_user where userid = ? and password = ? ";
// Statement stmt = conn.createStatement ();
PreparedStatement pstmt = conn.prepareStatement (sql);
pstmt.setString (1,userId);
pstmt.setString (2,inputPassword);
ResultSet rs = pstmt.executeQuery ();
if(rs.next ()){
String realName=rs.getString ("realname");
double money = rs.getDouble ("money");
user2 = new User (userId,realName,inputPassword,money);
return user2;
}
return user2;
}
}事务
public class TestTransation {
public static void main(String[] args) {
Connection conn=null;
try{
String driver = "com.mysql.cj.jdbc.Driver";
String url="jdbc:mysql://127.0.0.1:3306/shiyan?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
String user="root";
String pasaword="tcx119";
Class.forName (driver);
conn = DriverManager.getConnection (url,user,pasaword);
Statement stmt = conn.createStatement ();
conn.setAutoCommit (false);
stmt.executeUpdate ("update t_user set money = money-2000 where userid = 'lisi' ");
stmt.executeUpdate ("update t_user set money = money+2000 where userid = 'zhangsan' ");
conn.commit ();
} catch (ClassNotFoundException e) {
e.printStackTrace ();
} catch (SQLException e) {
//手动的回滚事务,回到所有DML操作执行之前的状态
try {
assert conn != null;
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace ();
}
}
}【都看到这了，点点赞点点关注呗，爱你们】😚😚
结语
谢谢你的阅读，由于作者水平有限，难免有不足之处，若读者发现问题，还请批评，在留言区留言或者私信告知，我一定会尽快修改的。若各位大佬有什么好的解法，或者有意义的解法都可以在评论区展示额，万分谢谢。
写作不易，望各位老板点点赞，加个关注!😘😘😘
