JMH generator: The function extension method of the annotation processor in the Java class library

JMH generator: The function extension method of the annotation processor in the Java class library JMH (Java Microbenchmark Harness) is a powerful benchmark testing tool for evaluating and measured the performance of Java code.JMH provides a simple but powerful method that can easily generate, execute, and analyze micro -base test.In this article, we will discuss how to use the JMH generator to extend the function of JMH so that we can better use the annotation processor in the Java class library. The annotation processor is part of the Java compiler, which is used to process and generate source code.They can read the annotations in the Java source file during compilation and generate additional code according to the annotation.The annotation processor is widely used in many Java libraries and frameworks to automatically generate code, realize dependency injection, and generate documents. The JMH generator is a tool expanded on the basis of the JMH framework. It provides a simple way that combines the annotation processor with the JMH micro -foundation test.By using the JMH generator, we can easily add annotations and generator logic to our test category to achieve stronger and more flexible benchmark tests. First, let's see a simple example to introduce how to use the JMH generator to expand the function of JMH.Suppose we have a custom annotation `@benchmarkconfig`, which are used to configure some parameters of the benchmark test, such as the number of iterations and the number of threads.We hope to read these annotations before running the benchmark test and generate the corresponding code according to the configuration. First of all, we need to define an annotation processor `BenchmarkConfigProcessor`. The processor is responsible for reading`@benchmarkconfig` and generate the corresponding code.The following is a simple example: import java.util.Set; import javax.annotation.processing.AbstractProcessor; import javax.annotation.processing.RoundEnvironment; import javax.annotation.processing.SupportedAnnotationTypes; import javax.lang.model.element.TypeElement; @SupportedAnnotationTypes("com.example.BenchmarkConfig") public class BenchmarkConfigProcessor extends AbstractProcessor { @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { // Project BenchmarkConfig Note and generate the corresponding code return true; } } Next, use the JMH generator in our test category to integrate the annotation processor.We can enable the JMH generator by adding ``@generateMicrobenchmark` annotations, and specify the class of the annotation processor: import org.openjdk.jmh.annotations.Benchmark; import org.openjdk.jmh.annotations.GenerateMicroBenchmark; import com.example.BenchmarkConfig; @BenchmarkConfig(iterations = 1000, threads = 4) @GenerateMicroBenchmark(processor = BenchmarkConfigProcessor.class) public class MyBenchmark { @Benchmark public void myBenchmarkMethod() { // Here is our benchmark test code } } In the above example, we use the parameters of the benchmark test of the benchmark for the configuration of the `@benchmarkConfig`, and associate the`@generateMicrobenchmark` with the annotation processor `BenchmarkConfigProcessor`.When running the benchmark test, the JMH generator will automatically scan our test class, find the `@generatedMicrobenchmark` annotation, and call the specified annotation processor during compilation. In this way, we can flexibly use the annotation processor to generate code in the JMH benchmark test.The annotation processor can generate any complex code according to our needs, so as to achieve more advanced functions, such as conditional generating, dynamic code generation, etc. In summary, the JMH generator provides us with a simple and powerful method that can expand the function of the JMH so that you can better use the annotation processor in the Java library.Through integrated annotation processor, we can easily generate the code required for the benchmark test and implement more advanced benchmark testing functions.If you often use JMH for performance measurement, learning and mastering the JMH generator will help you better use the annotation processor in the Java class library.