在Apache Flink中如何在循环的每次迭代中写入文件？

import org.apache.flink.api.common.functions.RichMapFunction;
import org.apache.flink.api.common.state.ValueState;
import org.apache.flink.api.common.state.ValueStateDescriptor;
import org.apache.flink.api.java.functions.KeySelector;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.sink.SinkFunction;
import org.apache.flink.util.Collector;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class IterationFileWriterExample {

    public static void main(String[] args) throws Exception {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        // 创建数据流
        DataStream<Integer> dataStream = env.fromElements(1, 2, 3, 4, 5);

        // 定义循环迭代算子
        DataStream<Integer> iteration = dataStream.iterate().withFeedbackType(Integer.class);

        // 在迭代算子中执行写入操作
        iteration.map(new RichMapFunction<Integer, Integer>() {
            private transient BufferedWriter writer;
            private ValueState<Integer> iterationCounter;

            @Override
            public void open(Configuration parameters) throws Exception {
                super.open(parameters);

                // 初始化写入器
                writer = new BufferedWriter(new FileWriter("/path/to/output.txt"));

                // 初始化迭代计数器状态
                iterationCounter = getRuntimeContext().getState(new ValueStateDescriptor<>("iterationCounter", Integer.class));
            }

            @Override
            public Integer map(Integer value) throws Exception {
                // 获取迭代计数器的当前值
                int currentIteration = iterationCounter.value() != null ? iterationCounter.value() : 0;

                // 执行写入操作
                writer.write("Iteration " + currentIteration + ": " + value);
                writer.newLine();

                // 更新迭代计数器的值
                iterationCounter.update(currentIteration + 1);

                return value;
            }

            @Override
            public void close() throws IOException {
                super.close();

                // 关闭写入器
                writer.close();
            }
        }).addSink(new SinkFunction<Integer>() {
            @Override
            public void invoke(Integer value, Context context) throws Exception {
                // 在迭代结束后的最后一次写入操作中获取迭代计数器的最终值
                int finalIteration = context.getBroadcastState(new ValueStateDescriptor<>("iterationCounter", Integer.class)).value();

                // 执行最后一次写入操作
                BufferedWriter finalWriter = new BufferedWriter(new FileWriter("/path/to/final_output.txt"));
                finalWriter.write("Final Iteration: " + finalIteration + ", Value: " + value);
                finalWriter.newLine();
                finalWriter.close();
            }
        });

        // 设置迭代条件
        iteration.closeWith(iteration.filter(value -> value < 5));

        env.execute("Iteration File Writer Example");
    }
}