用java代码来定时增量同步数据库表的实现代码

以下是一个用Java代码实现定时增量同步数据库表的示例：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

public class IncrementalSync {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydb";
    private static final String DB_USER = "root";
    private static final String DB_PASSWORD = "mypassword";
    private static final String SOURCE_TABLE = "source_table";
    private static final String DESTINATION_TABLE = "destination_table";
    private static final String LAST_SYNC_COLUMN = "last_sync";
    
    public static void main(String[] args) {
        Timer timer = new Timer();
        timer.scheduleAtFixedRate(new IncrementalSyncTask(), 0, 60 * 60 * 1000);
    }
    
    private static class IncrementalSyncTask extends TimerTask {
        public void run() {
            Connection sourceConn = null;
            Connection destConn = null;
            PreparedStatement selectStmt = null;
            PreparedStatement insertStmt = null;
            ResultSet rs = null;
            
            try {
                sourceConn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
                destConn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
                
                // Get the timestamp of the last sync from the destination table
                Timestamp lastSync = null;
                String selectLastSyncSql = "SELECT " + LAST_SYNC_COLUMN + " FROM " + DESTINATION_TABLE;
                PreparedStatement selectLastSyncStmt = destConn.prepareStatement(selectLastSyncSql);
                ResultSet lastSyncRs = selectLastSyncStmt.executeQuery();
                if (lastSyncRs.next()) {
                    lastSync = lastSyncRs.getTimestamp(1);
                }
                lastSyncRs.close();
                selectLastSyncStmt.close();
                
                // Select all rows from the source table that have been updated since the last sync
                String selectSql = "SELECT * FROM " + SOURCE_TABLE + " WHERE last_updated > ?";
                selectStmt = sourceConn.prepareStatement(selectSql);
                selectStmt.setTimestamp(1, lastSync);
                rs = selectStmt.executeQuery();
                
                // Insert the updated rows into the destination table
                String insertSql = "INSERT INTO " + DESTINATION_TABLE + " VALUES (?, ?, ?)";
                insertStmt = destConn.prepareStatement(insertSql);
                while (rs.next()) {
                    int id = rs.getInt("id");
                    String name = rs.getString("name");
                    Timestamp lastUpdated = rs.getTimestamp("last_updated");
                    insertStmt.setInt(1, id);
                    insertStmt.setString(2, name);
                    insertStmt.setTimestamp(3, lastUpdated);
                    insertStmt.executeUpdate();
                }
                
                // Update the timestamp of the last sync in the destination table
                String updateSql = "UPDATE " + DESTINATION_TABLE + " SET " + LAST_SYNC_COLUMN + " = ?";
                PreparedStatement updateStmt = destConn.prepareStatement(updateSql);
                updateStmt.setTimestamp(1, new Timestamp(System.currentTimeMillis()));
                updateStmt.executeUpdate();
                updateStmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                try { if (rs != null) rs.close(); } catch (SQLException e) { }
                try { if (selectStmt != null) selectStmt.close(); } catch (SQLException e) { }
                try { if (insertStmt != null) insertStmt.close(); } catch (SQLException e) { }
                try { if (sourceConn != null) sourceConn.close(); } catch (SQLException e) { }
                try { if (destConn != null) destConn.close(); } catch (SQLException e) { }
            }
        }
    }
}

该示例使用了Java的Scheduler API来定期执行一个任务，这个任务会连接源数据库和目标数据库，在目标数据库中记录上一次同步的时间戳，然后查询源数据库中有哪些行是在上一次同步之后更新过的，将这些行插入到目标数据库中，并更新目标数据库中的时间戳。可以根据需要修改源数据库、目标数据库、表名、时间戳列名等参数。