Java中AutoCloseable接口使用小结

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class AutoCloseableExample {
    public static void main(String[] args) {
        String filePath = "example.txt";
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 注意：这里不需要显式调用 br.close()，因为 try-with-resources 会自动处理
    }
}

import lombok.extern.slf4j.Slf4j;

/**
 * 性能追踪工具类
 *
 * @author asurplus
 */
@Slf4j
public class PerfTracker {

    private final long startTime;
    private final String methodName;

    private PerfTracker(String methodName) {
        this.startTime = System.currentTimeMillis();
        this.methodName = methodName;
    }

    public static TimerContext start() {
        StackTraceElement stackTrace = Thread.currentThread().getStackTrace()[2];
        String[] split = stackTrace.getClassName().split("\\.");
        String s = "at " + stackTrace.getClassName() + "." + stackTrace.getMethodName() + "(" + split[split.length - 1] + ".java:" + stackTrace.getLineNumber() + ")";
        return new TimerContext(s);
    }

    public static class TimerContext implements AutoCloseable {
        private final PerfTracker tracker;

        private TimerContext(String methodName) {
            this.tracker = new PerfTracker(methodName);
        }

        @Override
        public void close() {
            long executeTime = System.currentTimeMillis() - tracker.startTime;
            if (executeTime > 500) {
                log.warn("慢sql查询告警：{} 耗时 {}ms", tracker.methodName, executeTime);
            }
        }
    }
}

public static void main(String[] args) {
    try (PerfTracker.TimerContext ignored = PerfTracker.start()) {
        sysUserMapper.list();
    }
}