@EnableAsync @Async

One . Basic introduction

@Async yes spring In order to facilitate developers to make asynchronous calls , Add this annotation to the method ,spring A new thread will be obtained from the thread pool to execute the method , Implement asynchronous call

@EnableAsync Indicates that support for asynchronous tasks is enabled , Can be placed in springboot On the startup class of , It can also be placed on the configuration class of the custom thread pool , See below for details

Two . Simplest use

stay springboot In the project , Add... Directly to the startup class @EnableAsync, And then in service For methods that need asynchronous invocation, add @Async,

So when controller When the layer calls this method , It will automatically create a new thread outside the main thread to execute this method , See the figure below for details. demo

1.springboot The startup class enables asynchronous support

 2.service Layer method plus @Async, If you add this annotation to a class, it means that the methods of the whole class are executed asynchronously , It is suggested to add it to a specific method

 3.controller Layer calls service Asynchronous method of layer , Here, the main thread is used to execute before and after the asynchronous method 2 Print out times

 4. The result of the call

First, let's see that there is no asynchronous execution , The result of normal sequential execution

You can see , Execute in order , All is main Threads http-nio-8181-exec-124 perform , also service The execution result of the method is in the middle , As shown below

  Because our method uses @Async annotation , So the main thread http-nio-8181-exec-124 Unequal asynchronous method completion , End first , Asynchronous thread task-1 Carry on

 

tips： There is no custom thread pool @Async The default thread pool is SimpleAsyncTaskExecutor

3、 ... and . Customize the thread pool to use @Async

1. Create a new thread pool configuration class ,@EnableAsync Add... To the configuration class , Don't add it to the startup class , Different thread pools can be configured , use bean Of name Make a distinction

 

 [email protected] The same is used in service Add , If multiple thread pools are configured , It can be used @Async("name"), Then it represents the thread pool @Bean Of name, To specify which thread pool to use

Suppose only one thread pool is configured , Direct use @Async It will execute with a custom thread pool

Suppose multiple thread pools are configured , use @Async No thread pool is specified , Will use the default SimpleAsyncTaskExecutor To deal with it

  Suppose multiple thread pools are configured , use @Async("name"), Will process with the specified thread pool

such as service Specify pool1 Thread pool

  Execution results , The asynchronous thread name is pool Configured fzhThread

 

https://www.cnblogs.com/fzhblog/p/14012401.html

  Four . The reason why the annotation did not take effect

1. The asynchronous method uses static modification

2. Asynchronous method classes are not used @Service annotation （ Or other comments ） Lead to spring Cannot scan to asynchronous class

3.controller Required in @Autowired or @Resource Wait for the annotation to inject automatically service class , You can't do it by yourself new object

When we use multithreading , Often need to create Thread class , Or realize Runnable Interface , To create Executors, In the use of spring in , Has given us good support , Just use @Async You can define a thread task . adopt spring For us ThreadPoolTaskExecutor You can use thread pool .

By default ,Spring Relevant thread pool definitions will be searched ： Or search for the only one in the context TaskExecutor bean, Or search for the name “taskExecutor” Of Executor bean. If both cannot be resolved , Will use SimpleAsyncTaskExecutor To handle asynchronous method calls .