二阶段提交：确保分布式系统中数据一致性的关键协议

java复制代码
import java.sql.Connection;  
import java.sql.DriverManager;  
import java.sql.PreparedStatement;  
import java.sql.SQLException;  
import java.util.ArrayList;  
import java.util.List;  
public class TwoPhaseCommit {  
// 模拟参与者列表  
private List<Participant> participants = new ArrayList<>();  
// 模拟协调者  
private Coordinator coordinator = new Coordinator();  
// 初始化参与者  
public TwoPhaseCommit() {  
        participants.add(new Participant("jdbc:mysql://localhost:3306/db1", "user", "password"));  
        participants.add(new Participant("jdbc:mysql://localhost:3306/db2", "user", "password"));  
// 可以添加更多参与者  
    }  
// 执行两阶段提交  
public void execute() {  
try {  
// 准备阶段  
            coordinator.prepare(participants);  
// 提交阶段  
            coordinator.commit(participants);  
            System.out.println("事务提交成功！");  
        } catch (Exception e) {  
// 出现异常，进行回滚  
try {  
                coordinator.rollback(participants);  
            } catch (SQLException e1) {  
                e1.printStackTrace();  
            }  
            System.out.println("事务回滚！");  
        }  
    }  
// 协调者类  
private class Coordinator {  
public void prepare(List<Participant> participants) throws SQLException {  
for (Participant participant : participants) {  
                participant.prepare();  
            }  
        }  
public void commit(List<Participant> participants) throws SQLException {  
for (Participant participant : participants) {  
                participant.commit();  
            }  
        }  
public void rollback(List<Participant> participants) throws SQLException {  
for (Participant participant : participants) {  
                participant.rollback();  
            }  
        }  
    }  
// 参与者类  
private class Participant {  
private Connection connection;  
public Participant(String url, String user, String password) {  
try {  
                connection = DriverManager.getConnection(url, user, password);  
                connection.setAutoCommit(false); // 开启事务  
            } catch (SQLException e) {  
                e.printStackTrace();  
            }  
        }  
public void prepare() throws SQLException {  
// 模拟执行事务操作（但不提交）  
String sql = "UPDATE some_table SET some_column = ? WHERE some_condition = ?";  
try (PreparedStatement statement = connection.prepareStatement(sql)) {  
                statement.setString(1, "new_value");  
                statement.setString(2, "some_condition");  
                statement.executeUpdate();  
// 投票“同意”  
                System.out.println("参与者投票：同意");  
            }  
        }  
public void commit() throws SQLException {  
// 提交事务  
            connection.commit();  
            System.out.println("参与者提交事务");  
        }  
public void rollback() throws SQLException {  
// 回滚事务  
            connection.rollback();  
            System.out.println("参与者回滚事务");  
        }  
    }  
public static void main(String[] args) {  
TwoPhaseCommit twoPhaseCommit = new TwoPhaseCommit();  
        twoPhaseCommit.execute();  
    }  
}