写一段java线程监控sybase表变更的代码，并将变更字段结果用json输出，注意表没有唯一键

以下是一段Java代码，用于监控Sybase表的变更，并将变更字段结果用JSON格式输出。该代码使用JDBC连接到Sybase数据库，并使用JDBC API获取表的元数据和数据。然后，它使用Java线程来监视表的变更。

import java.sql.*;
import java.util.*;
import java.util.concurrent.*;
import com.fasterxml.jackson.databind.ObjectMapper;

public class SybaseTableMonitor {

    private static final String DB_URL = "jdbc:sybase:Tds:host:port/database";
    private static final String DB_USER = "user";
    private static final String DB_PASSWORD = "password";
    private static final String TABLE_NAME = "table_name";

    private static final int POLL_INTERVAL = 5000; // 5 seconds
    private static final ObjectMapper MAPPER = new ObjectMapper();

    private static ExecutorService executor = Executors.newSingleThreadExecutor();
    private static volatile boolean running = true;

    public static void main(String[] args) throws Exception {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        List<String> columnNames = new ArrayList<>();
        Map<String, Object> lastRow = new HashMap<>();

        try {
            conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
            stmt = conn.createStatement();
            rs = stmt.executeQuery("SELECT * FROM " + TABLE_NAME + " WHERE 1=0"); // get metadata only
            ResultSetMetaData meta = rs.getMetaData();
            int numColumns = meta.getColumnCount();
            for (int i = 1; i <= numColumns; i++) {
                columnNames.add(meta.getColumnName(i));
            }
        } catch (SQLException e) {
            e.printStackTrace();
            return;
        } finally {
            if (rs != null) rs.close();
            if (stmt != null) stmt.close();
        }

        Runnable task = new Runnable() {
            public void run() {
                try {
                    while (running) {
                        stmt = conn.createStatement();
                        rs = stmt.executeQuery("SELECT TOP 1 * FROM " + TABLE_NAME + " ORDER BY 1 DESC");
                        if (rs.next()) {
                            Map<String, Object> row = new HashMap<>();
                            for (String columnName : columnNames) {
                                Object value = rs.getObject(columnName);
                                row.put(columnName, value);
                            }
                            if (!lastRow.equals(row)) {
                                String json = MAPPER.writeValueAsString(row);
                                System.out.println(json);
                                lastRow = row;
                            }
                        }
                        rs.close();
                        stmt.close();
                        Thread.sleep(POLL_INTERVAL);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };

        executor.execute(task);

        // Wait for user to stop the program
        System.out.println("Press Enter to stop monitoring...");
        System.in.read();
        running = false;
        executor.shutdown();
        executor.awaitTermination(10, TimeUnit.SECONDS);
    }
}

该代码首先连接到Sybase数据库，并获取指定表的元数据，包括列名。然后，它启动一个Java线程，该线程使用JDBC API监视表的变更。在每次轮询时，该线程查询表的最新记录，并将其与上一次记录进行比较。如果有变更，则将结果输出为JSON格式。最后，该代码等待用户按Enter键停止监视线程。

请注意，该代码假定表中的数据类型是可序列化的，并且没有唯一键。如果表中包含非可序列化的数据类型，或者具有唯一键，则需要进行更改。此外，该代码可能会因为表中的大量变更而导致性能问题。在这种情况下，可以使用更高级的技术，例如Sybase的触发器或更高级的监视工具。