2024-01-开发技术积累

递归删除文件

xxl-job源码

   public static boolean deleteRecursively(File root) {
        if (root != null && root.exists()) {
            if (root.isDirectory()) {
                File[] children = root.listFiles();
                if (children != null) {
                    for (File child : children) {
                        deleteRecursively(child);
                    }
                }
            }
            return root.delete();
        }
        return false;
    }

执行任务超时时间

xxl-job源码

	if (triggerParam.getExecutorTimeout() > 0) {
						// limit timeout
						Thread futureThread = null;
						try {
              //创建一个执行任务线程
							FutureTask<Boolean> futureTask = new FutureTask<Boolean>(new Callable<Boolean>() {
								@Override
								public Boolean call() throws Exception {

									// init job context
									XxlJobContext.setXxlJobContext(xxlJobContext);

									handler.execute();
									return true;
								}
							});
							futureThread = new Thread(futureTask);
							futureThread.start();
             //通过线程的超时机制，来实现任务超时
							Boolean tempResult = futureTask.get(triggerParam.getExecutorTimeout(), TimeUnit.SECONDS);
				} 

读写锁

ReentrantReadWriteLock

以下代码 来自官方文档

class RWDictionary {
   private final Map<String, Data> m = new TreeMap<String, Data>();
   private final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
   private final Lock r = rwl.readLock();
   private final Lock w = rwl.writeLock();

   public Data get(String key) {
     r.lock();
     try { return m.get(key); }
     finally { r.unlock(); }
   }
   public String[] allKeys() {
     r.lock();
     try { return m.keySet().toArray(); }
     finally { r.unlock(); }
   }
   public Data put(String key, Data value) {
     w.lock();
     try { return m.put(key, value); }
     finally { w.unlock(); }
   }
   public void clear() {
     w.lock();
     try { m.clear(); }
     finally { w.unlock(); }
   }
 }

获取异常栈信息

StringWriter stringWriter = new StringWriter();
e.printStackTrace(new PrintWriter(stringWriter));
String errorMsg = stringWriter.toString();

通过NIO读取文件

nacos源码中，如果是多实例，就采用nio读取文件

 public static String getFileContent(File file, String charsetName) throws IOException {
        RandomAccessFile fis = null;
        FileLock rlock = null;
        try {
            fis = new RandomAccessFile(file, "r");
            FileChannel fcin = fis.getChannel();
            int i = 0;
            do {
                try {
                    rlock = fcin.tryLock(0L, Long.MAX_VALUE, true);
                } catch (Exception e) {
                    ++i;
                    if (i > RETRY_COUNT) {
                        LOGGER.error("read {} fail;retryed time:{}", file.getName(), i);
                        throw new IOException("read " + file.getAbsolutePath() + " conflict");
                    }
                    sleep(SLEEP_BASETIME * i);
                    LOGGER.warn("read {} conflict;retry time:{}", file.getName(), i);
                }
            } while (null == rlock);
            int fileSize = (int) fcin.size();
            ByteBuffer byteBuffer = ByteBuffer.allocate(fileSize);
            fcin.read(byteBuffer);
            byteBuffer.flip();
            return byteBufferToString(byteBuffer, charsetName);
        } finally {
            if (rlock != null) {
                rlock.release();
                rlock = null;
            }
            if (fis != null) {
                fis.close();
                fis = null;
            }
        }
    }
    
    public static String byteBufferToString(ByteBuffer buffer, String charsetName) throws IOException {
        Charset charset = null;
        CharsetDecoder decoder = null;
        CharBuffer charBuffer = null;
        charset = Charset.forName(charsetName);
        decoder = charset.newDecoder();
        charBuffer = decoder.decode(buffer.asReadOnlyBuffer());
        return charBuffer.toString();
    }

单例模式代码

public final class GlobalAdvisorAdapterRegistry {

	private GlobalAdvisorAdapterRegistry() {
	}


	/**
	 * Keep track of a single instance so we can return it to classes that request it.
	 */
	private static AdvisorAdapterRegistry instance = new DefaultAdvisorAdapterRegistry();

	/**
	 * Return the singleton {@link DefaultAdvisorAdapterRegistry} instance.
	 */
	public static AdvisorAdapterRegistry getInstance() {
		return instance;
	}

	/**
	 * Reset the singleton {@link DefaultAdvisorAdapterRegistry}, removing any
	 * {@link AdvisorAdapterRegistry#registerAdvisorAdapter(AdvisorAdapter) registered}
	 * adapters.
	 */
	static void reset() {
		instance = new DefaultAdvisorAdapterRegistry();
	}

}

NIO管道写文件(来自nacos)

nacos raft协议 写文件

        ByteBuffer data;
        //通过nio  管道写文件
        data = ByteBuffer.wrap(JacksonUtils.toJson(datum).getBytes(StandardCharsets.UTF_8));

        try (FileChannel fc = new FileOutputStream(cacheFile, false).getChannel()) {
            fc.write(data, data.position());
            fc.force(true);
        } catch (Exception e) {
            MetricsMonitor.getDiskException().increment();
            throw e;
        }

NIO读取文件(来自Nacos)

数据恢复,从文件中加载数据

        ByteBuffer buffer;
        try (FileChannel fc = new FileInputStream(file).getChannel()) {
            //申请内存空间
            buffer = ByteBuffer.allocate((int) file.length());
            //读数据到buffer
            fc.read(buffer);

            String json = new String(buffer.array(), StandardCharsets.UTF_8);
            if (StringUtils.isBlank(json)) {
                return null;
            }
            
          }

spring指定注解扫描

 ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
      if (this.resourceLoader != null) {
        scanner.setResourceLoader(this.resourceLoader);
      }
      //只扫描Mapper.class注解
      scanner.setAnnotationClass(Mapper.class);
      scanner.registerFilters();
      scanner.doScan(StringUtils.toStringArray(packages));