MySQL learning records 12jdbc operation transactions

MySQL Learning record 12JDBC Operational transaction

ACID principle

• Atomicity ： Or it's all done , Or it's not done
• Uniformity ： The total remains unchanged
• persistence ： Once submitted, it's irreversible , Persistent to the database
• Isolation, ： Multiple processes do not interfere with each other

The problem of isolation

• Dirty reading ： One transaction reads another uncommitted transaction
• It can't be read repeatedly ： In the same business , Repeatedly read the data in the table , Table data has changed
• Virtual reading ( Fantasy reading )： In a business , Read the data inserted by others , The results read before and after are inconsistent

Code implementation

• First step ： Open transaction （conn.setAutoCommit(false);）
• The second step ： After the execution of a group of business , Commit transaction （conn.commit();）
• The third step ： Can be in catch Statement to define the rollback statement , But the default failure will also be rolled back （conn.rollback();）

sql Create table statement ：

CREATE TABLE account
(
    id    Int PRIMARY KEY AUTO_INCREMENT,
    NAME  VARCHAR(40),
    money FLOAT
);

/* Insert test data */
insert into account(name, money)
values ('A', 1000);
insert into account(name, money)
values ('B', 1000);
insert into account(name, money)
values ('C', 1000);

import com.jatine.lesson02.utils.JdbcUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class TestTransaction1 {
    
    public static void main(String[] args) throws SQLException {
    
        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;

        try {
    
            conn = JdbcUtils.getConnection();
            // Turn off automatic submission of the database , Automatically opens the transaction 

            conn.setAutoCommit(false);  // Open transaction 

            String sql1 = "update account set money = money - 100 where name = 'A'";
            st = conn.prepareStatement(sql1);
            st.executeUpdate();

            String sql2 = "update account set money = money + 100 where name = 'B'";
            st = conn.prepareStatement(sql2);
            st.executeUpdate();

            // Business finished , Commit transaction 
            conn.commit();
            System.out.println(" success ！");

        } catch (SQLException e) {
    

            // If it fails, roll back the transaction 
            try {
    
                conn.rollback(); // Even if there is no such sentence , If it fails, it is also the default rollback 
            } catch (SQLException throwables) {
    
                throwables.printStackTrace();
            }
            e.printStackTrace();
        } finally {
    
            JdbcUtils.release(conn, st, rs);
        }
    }
}

Simulate failure scenarios ：

            String sql1 = "update account set money = money - 100 where name = 'A'";
            st = conn.prepareStatement(sql1);
            st.executeUpdate();

            int x = 1 / 0; // Report errors 

            String sql2 = "update account set money = money + 100 where name = 'B'";
            st = conn.prepareStatement(sql2);
            st.executeUpdate();

Report errors ：

The data has not changed ：