场地的春季

INFLUX_DB_SERVER reportMemory 做了大量的工作,它构建了一个度量和执行调用 reportAll ,在没有流入的情况下,所有这些工作都是无用的。

我能做的就是写一个方法 isWorkPossible 并在每次调用时调用该方法。那可能是接吻之后的事,但那违反了干燥。所以我喜欢用AOP来实现。

/**
 * The reporter to notify {@link InfluxDB influxDBs} for changes.
 */
@Named
public class InfluxDBReporter {
    /**
     * Logger for reporting. For security reasons neither the username nor the
     * password should be logged above {@link Level#FINER}.
     */
    private static final Logger LOG = Logger.getLogger(InfluxDBReporter.class.getCanonicalName());

    /**
     * The entitymanager to use, never <code>null</code>.
     */
    @PersistenceContext
    private final EntityManager entityManager = null;

    /**
     * The registred {@link InfluxDBServer} in key and the URL in value.
     */
    @SkipPublicVoidMethodsIfEmpty
    private final Map<InfluxDB, URL> dbs = new LinkedHashMap<>();

    /**
     * Initializes the connections.
     */
    @PostConstruct
    private void connect() {
        for (InfluxDBServer db : FROM(囗InfluxDBServer.class).all(entityManager)) {
            try {
                URL dbUrl = new URL(db.getUrl());
                InfluxDB idb = InfluxDBFactory.connect(db.getUrl(), db.getUsername(), db.getPassword());
                idb.setDatabase(db.getDatabaseName());
                dbs.put(idb, dbUrl);
            } catch (MalformedURLException e) {
                LOG.log(Level.SEVERE, db.getUrl(), e);
            }
        }
    }

    /**
     * Closes all connections to all {@link InfluxDB}.
     */
    @PreDestroy
    private void disconnect() {
        for (InfluxDB influxDB : dbs.keySet()) {
            try {
                influxDB.close();
            } catch (Exception e) {
                // Fault barrier
                LOG.log(Level.WARNING, "InfluxDBServer URL: " + dbs.get(idb), e);
            }
        }
    }

    /**
     * Report memory statistics.
     * 
     * @param availableProcessors Amount of available processors, never negative.
     * @param totalMemory         The total memory, never negative.
     * @param maxMemory           The max memory, never negative.
     * @param freeMemory          The free memory, never negative.
     */
    public void reportMemory(int availableProcessors, long totalMemory, long maxMemory, long freeMemory) {
        reportAll(Point.measurement("jvm").addField("totalMemory", totalMemory).addField("maxMemory", maxMemory)
                .addField("freeMemory", freeMemory));
    }

    /**
     * Report a point to all connected {@link InfluxDBServer}.
     * 
     * @param builder The point to report.
     */
    private void reportAll(Builder builder) {
        Point infoPoint = builder.time(System.currentTimeMillis(), TimeUnit.MILLISECONDS).build();
        for (InfluxDB idb : dbs.keySet()) {
            new Thread(() -> {
                try {
                    idb.write(infoPoint);
                } catch (Exception e) {
                    // Fault barrier
                    LOG.log(Level.WARNING, "InfluxDBServer URL: " + dbs.get(idb), e);
                    throw e;
                }
            }).start();
        }
    }
}

@Aspect
public class MethodAnnotations {
    @Pointcut("@annotation(xxx.MethodAnnotations.SkipPublicVoidMethodsIfEmpty)")
    private void anyOldTransfer(JoinPoint jp) {
        System.out.println(jp); <----- never executed.
    }

    public @interface SkipPublicVoidMethodsIfEmpty {
    }
}

我希望 System.out.println 在bean被实例化但没有实例化时运行。

知道为什么吗?