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ClickHouse官网文档

Flink 读取 ClickHouse 数据两种驱动

1. ClickHouse 官方提供Clickhouse JDBC.【建议使用】
2. 第3方提供的Clickhouse JDBC. ru.yandex.clickhouse.ClickHouseDriver

ru.yandex.clickhouse.ClickHouseDriver.现在是没有维护

ClickHouse 官方提供Clickhouse JDBC的包名：com.clickhouse.jdbc.*

有些版本com.clickhouse.jdbc.* 包含了 ru.yandex.clickhouse.ClickHouseDriver.

因此加载包的时候一定要注意导入的包名

引入依赖

        <!-- clickhouse jdbc driver --><dependency><groupId>com.clickhouse</groupId><artifactId>clickhouse-jdbc</artifactId></dependency>

使用的是 0.3 这个版本，该版本就包含上述3方CH jdbc包

     <!-- CH JDBC版本推荐使用 0.3, 0.4的版本是要 JDK 17 --><clickhouse-jdbc.version>0.3.2-patch11</clickhouse-jdbc.version>

自定义Source

测试表映射实体类，该表仅有一个name字段

@Data
@NoArgsConstructor
@AllArgsConstructor
public class CHTestPO {private String name;}

Flink Clickhouse Source

public class ClickHouseSource implements SourceFunction<CHTestPO> {private final String URL;private final String SQL;public ClickHouseSource(String URL, String SQL) {this.URL = URL;this.SQL = SQL;}@Overridepublic void run(SourceContext<CHTestPO> output) throws Exception {//  Properties是持久化的属性集 Properties的key和value都是字符串Properties properties = new Properties();ClickHouseDataSource clickHouseDataSource = new ClickHouseDataSource(URL, properties);// 使用 try-with-resource 方式关闭JDBC连接 无需手动关闭try (ClickHouseConnection conn = clickHouseDataSource.getConnection()) {// clickhouse 通过游标的方式读取数据Statement stmt = conn.createStatement();ResultSet rs = stmt.executeQuery(SQL);while (rs.next()) {String name = rs.getString(1);output.collect(new CHTestPO(name));}}}@Overridepublic void cancel() {}
}

自定义Sink

需额外引入依赖

        <!-- Flink-Connector-Jdbc --><dependency><groupId>org.apache.flink</groupId><artifactId>flink-connector-jdbc_${scala.binary.version}</artifactId></dependency>

Java 对sql语句处理的两个对象

1. PreparedStatement对象：能够对预编译之后的sql语句进行处理【SQL 语句预编译：通过占位符'?'实现，可以防止sql注入】
2. Statement对象：只能对静态的sql语句进行处理

核心代码

/*** 使用 Flink-jdbc-connector + 批量写入 + sql语句的预编译 写入 Clickhouse*/
public class ClickHouseJdbcSink<T> {private final SinkFunction<T> sink;private final static String NA = "null";public ClickHouseJdbcSink(String sql, int batchSize, String url) {sink = JdbcSink.sink(sql,// 对sql语句进行预编译new ClickHouseJdbcStatementBuilder<T>(),// 设置批量插入数据new JdbcExecutionOptions.Builder().withBatchSize(batchSize).build(),// 设置ClickHouse连接配置new JdbcConnectionOptions.JdbcConnectionOptionsBuilder().withUrl(url).build());}public SinkFunction<T> getSink() {return this.sink;}/*** 对预编译之后的sql语句进行占位符替换** @param ps:     PreparedStatement对象 下标从 1 开始* @param fields: clickhouse表PO对象的属性字段* @param object: clickhouse表PO对象的属性字段所对应的数据类型*/public static void setPreparedStatement(PreparedStatement ps,Field[] fields,Object object) throws IllegalAccessException, SQLException {// 遍历 Field[]for (int i = 1; i <= fields.length; i++) {// 取出每个Field实例Field field = fields[i - 1];// 指示反射的对象在使用时应该取消 Java 语言访问检查field.setAccessible(true);// 通过Field实例的get方法返回指定的对象Object o = field.get(object);if (o == null) {ps.setNull(i, 0);continue;}// 这里统一设为字符型String fieldValue = o.toString();// 变量和常量的比较，通常将常量放前，可以避免空指针if (!NA.equals(fieldValue) && !"".equals(fieldValue)) {// 替换对应位置的占位符ps.setObject(i, fieldValue);} else {ps.setNull(i, 0);}}}}

对sql语句进行预编译

@Slf4j
public class ClickHouseJdbcStatementBuilder<T> implements JdbcStatementBuilder<T> {@Overridepublic void accept(PreparedStatement preparedStatement, T t) throws SQLException {/* *********************** Java通过反射获取类的字段：** 1. getDeclaredFields()：获取所有的字段，不会获取父类的字段* 2. getFields(): 只能会public字段，获取包含父类的字段** *********************/Field[] fields = t.getClass().getDeclaredFields();// 将获取到的字段替换sql预编译之后的占位符。try {ClickHouseJdbcSink.setPreparedStatement(preparedStatement, fields, t);} catch (IllegalAccessException e) {log.error("sql 预编译失败", e);e.printStackTrace();}}
}

ClickHouse读写工具类

public class ClickHouseUtil {private static final String URL;static {ParameterTool parameterTool = ParameterUtil.getParameters();URL = parameterTool.get("clickhouse.url");}/*** 读取clickhouse*/public static DataStream<CHTestPO> read(StreamExecutionEnvironment env, String sql) {return env.addSource(new ClickHouseSource(URL, sql));}/*** 批量写入ClickHouse*/public static <T> DataStreamSink<T> batchWrite(DataStream<T> dataStream,String sql,int batchSize) {//生成 SinkFunctionClickHouseJdbcSink<T> clickHouseJdbcSink =new ClickHouseJdbcSink<T>(sql, batchSize, URL);return dataStream.addSink(clickHouseJdbcSink.getSink());}}

测试一下

public class ClickHouseUtilTest {@DisplayName("测试Flink+jdbc+游标读取Clickhouse")@Testvoid testRead() throws Exception {StreamExecutionEnvironment env =StreamExecutionEnvironment.getExecutionEnvironment();// 设置并行度1env.setParallelism(1);// 从default数据库的user表中读取数据String sql = "select * from default.user";DataStream<CHTestPO> ds = ClickHouseUtil.read(env, sql);// 打印数据流中的元素ds.print("clickhouse");// 执行程序env.execute();}@DisplayName("测试Flink-Connector-jdbc+预编译批量写入Clickhouse")@Testvoid testBatchWrite() throws Exception {StreamExecutionEnvironment env =StreamExecutionEnvironment.getExecutionEnvironment();// 设置并行度1env.setParallelism(1);CHTestPO po = new CHTestPO();po.setName("Lucy");CHTestPO po1 = new CHTestPO();po1.setName("Jack");DataStream<CHTestPO> ds = env.fromCollection(Arrays.asList(po, po1));// 定义将数据写入ClickHouse数据库的SQL语句String sql = "insert into default.user(name) values(?)";// 调用ClickHouseUtil的batchWrite方法将数据流ds中的数据批量写入ClickHouse数据库ClickHouseUtil.batchWrite(ds, sql, 2);// 执行程序env.execute();}
}

此时表中仅一行记录

读取没有问题！

写入没有问题！