【Java优化实战】「微基准系列」带你脚踏实地的进行开发和使用JMH测试和提升应用程序和服务指南

<!-- JMH的核心包 https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-core -->
<dependency>
    <groupId>org.openjdk.jmh</groupId>
    <artifactId>jmh-core</artifactId>
    <version>1.35</version>
</dependency>
 <!-- JMH依赖注解,需要注解处理包 https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-generator-annprocess -->
<dependency>
    <groupId>org.openjdk.jmh</groupId>
    <artifactId>jmh-generator-annprocess</artifactId>
    <version>1.35</version>
</dependency>

@Benchmark
    public Object testString(BenchmarkState state) {
        return state.str.replace(TGT, REPLACEMENT);
    }
    @Benchmark
    public Object testStringUtils(BenchmarkState state) {
        return StringUtils.replace(state.str, TGT, REPLACEMENT);
    }
    @Benchmark
    public Object testLang3StringUtils(BenchmarkState state) {
        return org.apache.commons.lang3.StringUtils.replace(state.str, TGT, REPLACEMENT);
    }

@Benchmark
@BenchmarkMode(Mode.Throughput) // 吞吐量
public void measureThroughput() throws InterruptedException {
    /* 仅测试吞吐量 */
    TimeUnit.MILLISECONDS.sleep(100);
}
@Benchmark
@BenchmarkMode({Mode.Throughput, Mode.AverageTime, Mode.SampleTime})
public void measureMultiple() throws InterruptedException {
    /* 测试吞吐量、平均时间和抽样时间 */
    TimeUnit.MILLISECONDS.sleep(100);
}
@Benchmark
@BenchmarkMode(Mode.All)
public void measureAll() throws InterruptedException {
    /* 测试所有，即吞吐量、平均时间、抽样时间和启动时间 */
    TimeUnit.MILLISECONDS.sleep(100);
}

@OutputTimeUnit(TimeUnit.MILLISECONDS) // 结果所使用的时间单位
public class JmhExample{}

@Warmup(iterations = 5) // 先预热5轮
public class JmhSeample {}

@Measurement(iterations = 2) // 进行2轮测试
public class JmhSeample {}

@State(Scope.Thread) // 每个测试线程分配一个实例
public class JMHSample {
  public void prepare() {
        System.err.println("init............");
    }
}

@State(Scope.Thread)
public class JmhSample22 {
    @Setup(Level.Iteration)
    public void prepare() {
        System.err.println("init............");
    }
    @TearDown(Level.Iteration)
    public void check() {
        System.err.println("destroy............");
    }
    @Benchmark
    public void measureRight() {
        x++;
    }
}

@Fork(2) // Fork进行的数目
public class BenchMark {}

@Threads(4)
public class JmhTest {}

@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 3, time = 1)
@Measurement(iterations = 5, time = 5)
@Threads(4)
@Fork(1)
@State(value = Scope.Benchmark)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class JmhTest {}

@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 3, time = 1)
@Measurement(iterations = 5, time = 5)
@Threads(4)
@Fork(1)
@State(value = Scope.Benchmark)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class StringConnectTest {
    @Param(value = {"10", "50", "100"})
    private int length;
    @Benchmark
    public void testStringAdd(Blackhole blackhole) {
        String a = "";
        for (int i = 0; i < length; i++) {
            a += i;
        }
        blackhole.consume(a);
    }
    public static void main(String[] args) throws RunnerException {
        Options opt = new OptionsBuilder()
                .include(StringConnectTest.class.getSimpleName());
        new Runner(opt).run();
    }
}

<plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>2.4.1</version>
        <executions>
            <execution>
                <phase>package</phase>
                <goals>
                    <goal>shade</goal>
                </goals>
                <configuration>
                    <finalName>jmh-demo</finalName>
                    <transformers>
                        <transformer
                                implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                            <mainClass>org.openjdk.jmh.Main</mainClass>
                        </transformer>
                    </transformers>
                </configuration>
            </execution>
        </executions>
    </plugin>
</plugins>