📅  最后修改于: 2023-12-03 14:39:16.261000             🧑  作者: Mango
Apache Flink是一个高性能、分布式、可扩展的数据流处理框架。它可以处理和分析无限量的数据,支持数据流处理和批处理两种模式。
Flink提供了三种用于处理数据的API:
DataSet API通过提供各种操作符来处理有限数据集。这些操作符可以与Java、Scala和Python编程语言一起使用。
下面是一个简单的DataSet API示例,演示了如何读取并处理文本文件:
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
public class WordCount {
public static void main(String[] args) throws Exception {
final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
DataSet<String> text = env.readTextFile("/path/to/your/file")
.flatMap(new LineSplitter());
DataSet<Tuple2<String, Integer>> counts = text.groupBy(0).sum(1);
counts.print();
}
public static final class LineSplitter implements FlatMapFunction<String, Tuple2<String, Integer>> {
@Override
public void flatMap(String value, Collector<Tuple2<String, Integer>> out) {
for (String word : value.split("\\s")) {
out.collect(new Tuple2<String, Integer>(word, 1));
}
}
}
}
DataStream API通过提供各种操作符来处理无限数据流。这些操作符可以与Java、Scala一起使用。
下面是一个简单的DataStream API示例,演示了如何读取并处理套接字流:
import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.connectors.socket.SocketTextStreamFunction;
import org.apache.flink.util.Collector;
public class SocketTextStreamWordCount {
public static void main(String[] args) throws Exception {
final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
DataStream<String> text = env.socketTextStream("hostname", 9999);
DataStream<Tuple2<String, Integer>> counts = text.flatMap(new LineSplitter())
.keyBy(0)
.sum(1);
counts.print();
env.execute("Socket TextStream WordCount");
}
public static final class LineSplitter implements FlatMapFunction<String, Tuple2<String, Integer>> {
@Override
public void flatMap(String value, Collector<Tuple2<String, Integer>> out) {
for (String word : value.split("\\s")) {
out.collect(new Tuple2<String, Integer>(word, 1));
}
}
}
}
Table API & SQL提供了一种与传统关系型数据库相似的API和查询语言,它可以查询无限量的数据流和有限数据集。
下面是一个简单的Table API & SQL示例,用于查询数据流中不同单词的计数:
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.table.api.DataTypes;
import org.apache.flink.table.api.EnvironmentSettings;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.TableEnvironment;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
import org.apache.flink.table.functions.TableFunction;
import org.apache.flink.types.Row;
public class WordCount {
public static void main(String[] args) throws Exception {
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tableEnv = StreamTableEnvironment.create(
env,
EnvironmentSettings.newInstance().useBlinkPlanner().inStreamingMode().build()
);
tableEnv.createTemporaryView(
"words",
env.fromElements("Hello", "Flink", "Hello", "TableAPI", "TableAPI", "SQL")
.map(s -> Row.of(s)),
TableSchema.builder().field("word", DataTypes.STRING()).build()
);
Table results = tableEnv.sqlQuery("SELECT word, COUNT(*) FROM words GROUP BY word");
results.toRetractStream(Row.class).print();
env.execute("Word Count");
}
}
更多关于Flink API的信息可以在Flink官方网站上找到。