java之jmh初识及使用

最近有场景需要数据支撑json的toJsonString方法和java原生的toString方法的运行速度，因此选用了JMH测试工具。

以下代码大致意思是：初始化一个list集合，放入100个对象，然后遍历这个集合，调用fastjson的toJsonString方法和对象的toString方法。

这100个对象属性值拼接了list的下标，防止字符串常量池中存在相同的字符。

实体类代码：

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class TestDto {

    private Integer id;
    private String name;
    private String address;
    private Date date;
    private boolean aBoolean;
    private double aDouble;
    private float aFloat;


}

jmh测试代码如下：

import com.alibaba.fastjson.JSON;
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
import org.openjdk.jmh.runner.options.TimeValue;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@State(Scope.Thread)
public class JmhTest {

    private List list;

    /**
     * 初始化准备工作
     */
    @Setup(Level.Iteration)
    public void setUp() {
        this.list = new ArrayList<>();
        for (int i = 0; i < 100; i++) {
            TestDto testDto = TestDto.builder()
                    .id(i)
                    .name("xiaoming" + i)
                    .address("beijing" + i)
                    .date(new Date())
                    .aDouble(i)
                    .aBoolean(true)
                    .aFloat(i)
                    .build();
            list.add(testDto);
        }
    }

    /**
     * 方法1
     */
    @Benchmark
    public void toJSONStringTest() {
        for (TestDto testDto : list) {
            String res = JSON.toJSONString(testDto);
        }
    }

    /**
     * 方法2
     */
    @Benchmark
    public void toStringTest() {
        for (TestDto testDto : list) {
            String res = testDto.toString();
        }
    }

    public static void main(String[] args) throws RunnerException {

        final Options opts = new OptionsBuilder()
                .include(JmhTest.class.getSimpleName())
                .forks(1)
                // 多少次测量迭代
                .measurementIterations(10)
                // 每次测量迭代需要多长时间
                .measurementTime(TimeValue.microseconds(1000000L))
                // 进行多少次预热迭代
                .warmupIterations(1)
                // 每次预热迭代需要多长时间
                .warmupTime(TimeValue.microseconds(1000000L))
                .build();
        new Runner(opts).run();
    }
}

运行结果如下：

# JMH version: 1.19
# VM version: JDK 1.8.0_282, VM 25.282-b08
# VM invoker: D:\corretto-1.8.0_282\jre\bin\java.exe
# VM options: -javaagent:D:\IntelliJ IDEA 2020.3.3\lib\idea_rt.jar=56086:D:\IntelliJ IDEA 2020.3.3\bin -Dfile.encoding=UTF-8
# Warmup: 1 iterations, 1000000 us each
# Measurement: 10 iterations, 1000000 us each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Average time, time/op
# Benchmark: com.honor.wpshowdemo.serverone.test.JmhTest.toJSONStringTest

# Run progress: 0.00% complete, ETA 00:00:22
# Fork: 1 of 1
# Warmup Iteration   1: 977.533 us/op
Iteration   1: 66.566 us/op
Iteration   2: 61.137 us/op
Iteration   3: 66.597 us/op
Iteration   4: 54.270 us/op
Iteration   5: 54.927 us/op
Iteration   6: 53.950 us/op
Iteration   7: 54.212 us/op
Iteration   8: 54.328 us/op
Iteration   9: 54.574 us/op
Iteration  10: 54.343 us/op


Result "com.honor.wpshowdemo.serverone.test.JmhTest.toJSONStringTest":
  57.490 ±(99.9%) 7.924 us/op [Average]
  (min, avg, max) = (53.950, 57.490, 66.597), stdev = 5.241
  CI (99.9%): [49.566, 65.414] (assumes normal distribution)


# JMH version: 1.19
# VM version: JDK 1.8.0_282, VM 25.282-b08
# VM invoker: D:\corretto-1.8.0_282\jre\bin\java.exe
# VM options: -javaagent:D:\IntelliJ IDEA 2020.3.3\lib\idea_rt.jar=56086:D:\IntelliJ IDEA 2020.3.3\bin -Dfile.encoding=UTF-8
# Warmup: 1 iterations, 1000000 us each
# Measurement: 10 iterations, 1000000 us each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Average time, time/op
# Benchmark: com.honor.wpshowdemo.serverone.test.JmhTest.toStringTest

# Run progress: 50.00% complete, ETA 00:00:13
# Fork: 1 of 1
# Warmup Iteration   1: 105.282 us/op
Iteration   1: 80.594 us/op
Iteration   2: 64.168 us/op
Iteration   3: 63.157 us/op
Iteration   4: 63.548 us/op
Iteration   5: 63.345 us/op
Iteration   6: 64.605 us/op
Iteration   7: 63.592 us/op
Iteration   8: 63.363 us/op
Iteration   9: 64.166 us/op
Iteration  10: 63.580 us/op


Result "com.honor.wpshowdemo.serverone.test.JmhTest.toStringTest":
  65.412 ±(99.9%) 8.094 us/op [Average]
  (min, avg, max) = (63.157, 65.412, 80.594), stdev = 5.353
  CI (99.9%): [57.318, 73.505] (assumes normal distribution)


# Run complete. Total time: 00:00:25

Benchmark                 Mode  Cnt   Score   Error  Units
JmhTest.toJSONStringTest  avgt   10  57.490 ± 7.924  us/op
JmhTest.toStringTest      avgt   10  65.412 ± 8.094  us/op

Process finished with exit code 0

结论如下：

对象属性只有7个的时候，fastjson的toJsonString方法明显优于对像的toString方法。

ps：

不过，当对象属性更少时，toString方法是优于toJosnString方法，这个验证过程没有发出来，大家也可以自行验证。