java 代码 canal同步到clickhouse

以下是 Java 代码实现 Canal 同步数据到 ClickHouse 的基本步骤：

1. 导入 ClickHouse JDBC 驱动

<dependency>
    <groupId>ru.yandex.clickhouse</groupId>
    <artifactId>clickhouse-jdbc</artifactId>
    <version>0.3.0</version>
</dependency>

2. 编写 Canal Client

使用 Canal Client 订阅 MySQL 数据库的 binlog，获取增量数据，将数据写入到 ClickHouse 中。

public class CanalClient {

    public static void main(String[] args) {
        CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress("127.0.0.1", 11111),
                "example", "canal", "canal");
        connector.connect();
        connector.subscribe(".*\\..*");
        connector.rollback();

        while (true) {
            Message message = connector.getWithoutAck(1000);
            long batchId = message.getId();
            int size = message.getEntries().size();
            if (batchId == -1 || size == 0) {
                continue;
            }

            for (CanalEntry.Entry entry : message.getEntries()) {
                if (entry.getEntryType() == CanalEntry.EntryType.ROWDATA) {
                    handleRowData(entry.getStoreValue());
                }
            }

            connector.ack(batchId);
        }
    }

    private static void handleRowData(String storeValue) {
        CanalEntry.RowChange rowChange = null;
        try {
            rowChange = CanalEntry.RowChange.parseFrom(ByteString.copyFrom(storeValue.getBytes()));
        } catch (InvalidProtocolBufferException e) {
            e.printStackTrace();
        }

        if (rowChange == null) {
            return;
        }

        String database = rowChange.getDbschema();
        String table = rowChange.getTable();

        for (CanalEntry.RowData rowData : rowChange.getRowDatasList()) {
            if (rowData.getEventType() == CanalEntry.EventType.DELETE) {
                delete(database, table, rowData.getBeforeColumnsList());
            } else if (rowData.getEventType() == CanalEntry.EventType.INSERT) {
                insert(database, table, rowData.getAfterColumnsList());
            } else if (rowData.getEventType() == CanalEntry.EventType.UPDATE) {
                update(database, table, rowData.getBeforeColumnsList(), rowData.getAfterColumnsList());
            }
        }
    }

    private static void insert(String database, String table, List<CanalEntry.Column> columns) {
        String sql = "INSERT INTO " + database + "." + table + " (";
        String values = ") VALUES (";
        for (CanalEntry.Column column : columns) {
            sql += column.getName() + ",";
            values += "'" + column.getValue() + "',";
        }
        sql = sql.substring(0, sql.length() - 1);
        values = values.substring(0, values.length() - 1);
        sql += values + ")";
        executeSql(sql);
    }

    private static void update(String database, String table, List<CanalEntry.Column> beforeColumns, List<CanalEntry.Column> afterColumns) {
        String sql = "UPDATE " + database + "." + table + " SET ";
        for (int i = 0; i < beforeColumns.size(); i++) {
            if (!beforeColumns.get(i).getValue().equals(afterColumns.get(i).getValue())) {
                sql += afterColumns.get(i).getName() + "='" + afterColumns.get(i).getValue() + "',";
            }
        }
        sql = sql.substring(0, sql.length() - 1);
        sql += " WHERE ";
        for (CanalEntry.Column column : beforeColumns) {
            sql += column.getName() + "='" + column.getValue() + "' AND ";
        }
        sql = sql.substring(0, sql.length() - 5);
        executeSql(sql);
    }

    private static void delete(String database, String table, List<CanalEntry.Column> columns) {
        String sql = "DELETE FROM " + database + "." + table + " WHERE ";
        for (CanalEntry.Column column : columns) {
            sql += column.getName() + "='" + column.getValue() + "' AND ";
        }
        sql = sql.substring(0, sql.length() - 5);
        executeSql(sql);
    }

    private static void executeSql(String sql) {
        Connection connection = null;
        Statement statement = null;
        try {
            connection = DriverManager.getConnection("jdbc:clickhouse://localhost:8123/default", "default", "");
            statement = connection.createStatement();
            statement.execute(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}

其中，handleRowData 方法用于处理 binlog 数据，insert、update 和 delete 方法用于将数据写入到 ClickHouse 中，executeSql 方法用于执行 SQL 语句。

3. 启动 Canal Client

在 Java 项目中，运行 CanalClient 类的 main 方法，启动 Canal Client，开始订阅 MySQL 数据库的 binlog，将增量数据写入到 ClickHouse 中。