Deepen the principle of annotation processor in the JMH Generators framework
JMH Generators (Java Microbenchmark Harness Generators) is a tool for writing the benchmark test, which can automatically generate the code test code.In JMH Generators, the annotation processor is used to process the annotation defined by the user, and the corresponding benchmark test code is generated according to the annotation.
The annotation processor is a mechanism provided by the Java compiler to process the annotation during the compilation stage.It can scan the annotation in the source code and generate additional Java code according to the annotation.JMH Generators use the function of the annotation processor to indicate the definition of the benchmark test by using custom annotations, and then the annotation processor will automatically generate the corresponding benchmark test code according to these annotations.
First of all, we need to define a customized annotation to represent the benchmark test.The following is an example:
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface BenchmarkTest {
String name() default "";
int iterations() default 1;
int warmupIterations() default 0;
int batchSize() default 1;
}
In this example, we define an annotation called `Benchmarktest`, and specify some default values, such as the name, the number of iterations, the number of preheating iterations, and batch size of the test method.
Next, we can use custom annotations on the test method to mark the code we want to perform the benchmark test.For example:
public class MyBenchmark {
@BenchmarkTest(name = "MyBenchmarkTest")
public void myTest() {
// To perform the code for the benchmark test
}
}
When we compile this class, the annotation processor will scan the annotation in the source code and generate the corresponding benchmark test code.The generated code will include the call and collection of the benchmark test method.
Finally, we can use JMH to run the benchmark test.JMH will automatically run the benchmark test method and measure its performance indicators.The following is a simple example:
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
public class MyBenchmarkRunner {
public static void main(String[] args) throws Exception {
Options options = new OptionsBuilder()
.include(MyBenchmark.class.getSimpleName())
.build();
new Runner(options).run();
}
}
In this example, we created a `Options` object and configured the benchmark test class to run through the` Optionsbuilder`.We then use the `Runner` class to run the benchmark test.
In short, JMH Generators use the function of the annotation processor to generate the code for generating the benchmark test.By using a custom annotation method to mark the benchmark test method, the annotation processor will automatically generate the corresponding reference test code during the compilation stage, and you can use JMH to run these generated benchmark tests.In this way, we can easily write and run the benchmark test to evaluate the performance of the code.
