循环请求数据

//有时候我们需要无限循环获取数据，直到超时为止

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Collection;
import java.util.Map;


public class LoopRunner {


    private static final Logger logger = LoggerFactory.getLogger(LoopRunner.class);
    private final String NO_MESSAGES_FOUND = "No messages found yet";

    private static final int SLEEP_TIME = 500;
    private Long maxWait = 10000L;

    private boolean timedOut = false;

    public LoopRunner(long maxWait) {
        this.maxWait = maxWait;
    }

    public LoopRunner(Long maxWait) {
        this.maxWait = maxWait;
    }

    public <T> T run(LoopCondition<T> lc) {
        timedOut = false;
        T data = null;
        long started = System.currentTimeMillis();
        ProcessTimer processTimer = new ProcessTimer();
        while (System.currentTimeMillis() - started < maxWait) {
            String foundMessages = NO_MESSAGES_FOUND;
            data = lc.getData();
            if (lc.test(data)) {
                if (data instanceof Collection<?>) {
                    int totalCount = ((Collection<?>) data).size();
                    logMessageStateCounts(data, lc);
                    logger.info("Found " + totalCount + " expected number of messages");
                }
                return data;
            }
            try {
                if (data != null) foundMessages = logMessageStateCounts(data, lc);
                long millisecondsRemaining = maxWait - processTimer.getExecutionTimeInMilliseconds();
                if (millisecondsRemaining > 0)
                    logger.info(foundMessages + ", wait time so far: " + processTimer.getExecutionTime() + ", timing out in " + millisecondsRemaining + " ms, checking again in " + SLEEP_TIME + " ms");
                Thread.sleep(SLEEP_TIME);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
        logger.warn("Timed out - could not find expected number of messages");
        timedOut = true;
        return data;
    }

    public boolean isTimedOut() {
        return timedOut;
    }

    private <T> String logMessageStateCounts(T data, LoopCondition<T> lc) {
        Map<String, Integer> foundMessageStatusCounts = lc.getStatusCounts(data);
        if (foundMessageStatusCounts != null) {
            for (String status : foundMessageStatusCounts.keySet()) {
                return "Found " + foundMessageStatusCounts.get(status) + " messages with a status of " + status;
            }
        }
        return NO_MESSAGES_FOUND;
    }


}

 需要实现的接口：

 

import java.util.Map;


public interface LoopCondition<T> {
    boolean test(T data);
    T getData();
    Map<String, Integer> getStatusCounts(T foundMessages);
}