Optional<String> optional = Optional.ofNullable(userId); if(optional.isPresent()){ //把用户id存入threadloacl中 WmUser wmUser = new WmUser();这段代码是什么意思

这段代码是将一个可能为null的userId封装成Optional对象，然后判断Optional对象是否有值，如果有值就将userId存入ThreadLocal中。

ThreadLocal是Java中的一个线程局部变量，它为每个线程提供了一个独立的变量副本，线程之间互不干扰。在多线程环境下，使用ThreadLocal可以避免线程安全问题。在这段代码中，将userId存储在ThreadLocal中，可能是为了在当前线程中方便地获取该userId。同时，代码中还创建了一个WmUser对象，但是并没有将其用于后续操作，可能是为了后续使用该对象。

相关问题

Optional<String> optional = Optional.ofNullable(userId);

Optional<String> optional = Optional.ofNullable(userId);这段代码的意思是创建了一个可以包含null值的Optional对象。如果userId不为null，则Optional对象的值为userId；如果userId为null，则Optional对象为空。可以通过调用isPresent()方法来判断Optional对象是否为空。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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Optional<?> kafkaMessage = Optional.ofNullable(record.value());

This line of code creates an Optional object called "kafkaMessage" that may or may not contain a non-null value. The value of this Optional object is set to the result of calling the "ofNullable" method on the "record.value()" object.

The "ofNullable" method is a static method of the Optional class that takes a nullable value as its parameter and returns an Optional object that contains the value if it is non-null, or an empty Optional if the value is null.

By using the Optional class, this code ensures that any subsequent operations on the "kafkaMessage" object will not result in a NullPointerException if the underlying value is null.