翻译自：https://tech.io/playgrounds/929/reactive-programming-with-reactor-3/transform
Transform
Description
Reactor ships with several operators that can be used to transform data.
Reactor有几个可用于转换数据的运算符。
Practice
In the first place, we will capitalize a String. Since this is a simple 1-1
transformation with no expected latency, we can use the map operator with
a lambda transforming a T into a U.
首先，我们将字符串大写。由于这是一个简单的1-1转换，没有预期的延迟，我们可以使用map运算符和lambda将T转换为U。
// Capitalize the user username, firstname and lastname
Mono capitalizeOne(Mono mono) {
return mono.map(user -> {
return new User(user.getUsername().toUpperCase(), user.getFirstname().toUpperCase(), user.getLastname().toUpperCase());
});
}
We can use exactly the same code on a Flux, applying the mapping to each
element as it becomes available.
我们可以在Flux上使用完全相同的代码，在每个元素可用时应用映射。
// Capitalize the users username, firstName and lastName
Flux capitalizeMany(Flux flux) {
return flux.map(user -> new User(user.getUsername().toUpperCase(), user.getFirstname().toUpperCase(), user.getLastname().toUpperCase()));
}
Now imagine that we have to call a webservice to capitalize our String.
This new call can have latency so we cannot use the synchronous map anymore.
Instead, we want to represent the asynchronous call as a Flux or Mono,
and use a different operator: flatMap.
现在想象一下，我们必须调用一个webservice来大写字符串。这个新的调用可能有延迟，
因此我们不能再使用同步map。相反，我们希望Flux或Mono进行异步调用，并使用不同的运算符：flatMap。
flatMap takes a transformation Function that returns a Publisher
instead of a U. This publisher represents the asynchronous transformation to
apply to each element. If we were using it with map, we'd obtain a stream of
Flux. Not very useful.
flatMap采用一个转换函数，该函数返回一个Publisher，而不是一个U。该publisher表示应用于
每个元素的异步转换。如果我们将其与map一起使用，我们将获得一个Flux>流。不是很有用。
But flatMap on the other hand knows how to deal with these inner publishers:
it will subscribe to them then merge all of them into a single global output,
a much more useful Flux. Note that if values from inner publishers arrive
at different times, they can interleave in the resulting Flux.
但另一方面，flatMap知道如何处理这些内部发布者：它将订阅这些发布者，
然后将所有发布者合并为一个全局输出，这是一个更有用的Flux。
请注意，如果来自内部发布者的值在不同的时间到达，它们可以交叉插入到产生的Flux中。
// Capitalize the users username, firstName and lastName using #asyncCapitalizeUser
Flux asyncCapitalizeMany(Flux flux) {
return flux.flatMap(user -> Flux.just(new User(user.getUsername().toUpperCase(), user.getFirstname().toUpperCase(), user.getLastname().toUpperCase())));
}