Apache Flink:如何将模式从一个源应用到另一个数据流？

import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.cep.CEP;
import org.apache.flink.cep.PatternSelectFunction;
import org.apache.flink.cep.PatternStream;
import org.apache.flink.cep.pattern.Pattern;
import org.apache.flink.cep.pattern.conditions.SimpleCondition;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;

public class PatternMatchingExample {

    public static void main(String[] args) throws Exception {
        // 创建执行环境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        // 创建数据流
        DataStream<Tuple2<String, Integer>> input = env.fromElements(
                new Tuple2<>("A", 1),
                new Tuple2<>("B", 2),
                new Tuple2<>("C", 3),
                new Tuple2<>("D", 4),
                new Tuple2<>("E", 5)
        );

        // 定义模式
        Pattern<Tuple2<String, Integer>, ?> pattern = Pattern.<Tuple2<String, Integer>>begin("start")
                .where(new SimpleCondition<Tuple2<String, Integer>>() {
                    @Override
                    public boolean filter(Tuple2<String, Integer> value) throws Exception {
                        return value.f1 > 2;
                    }
                });

        // 应用模式到数据流
        PatternStream<Tuple2<String, Integer>> patternStream = CEP.pattern(input, pattern);

        // 选择匹配的结果
        DataStream<String> result = patternStream.select(new PatternSelectFunction<Tuple2<String, Integer>, String>() {
            @Override
            public String select(Map<String, List<Tuple2<String, Integer>>> pattern) throws Exception {
                Tuple2<String, Integer> startEvent = pattern.get("start").get(0);
                return startEvent.f0;
            }
        });

        // 打印结果
        result.print();

        // 执行任务
        env.execute("Pattern Matching Example");
    }
}