Java

2023.04.03

SpringBootで非同期処理ができた

このSpringBootをDockerで動かす方法
1. https://github.com/Yuzunoha/SpringBootAsync1 のメインブランチをチェックアウトする
2. 直下で make release-up を実行する(make コマンドが無かったら入れて)。ビルドが始まるのでしばらく待つ
3. curl localhost を実行するとレスポンスが返ってくる

コーディングの注意点
completableFuture.join() をやった時点でスレッドが止まるので、join()は最後にまとめてやらないと非同期にならない。
例えばこんな風にしてはダメ。

createCompletableFuture(...).join();
createCompletableFuture(...).join();
createCompletableFuture(...).join();

createCompletableFuture(...).join();

こうするべし

var a = createCompletableFuture(...);
var b = createCompletableFuture(...);
var c = createCompletableFuture(...);
a.join();
b.join();
c.join();

var a = createCompletableFuture(...);

var b = createCompletableFuture(...);

var c = createCompletableFuture(...);

a.join();

b.join();

c.join();

以下検証コード。Anno0Wrap1の書き方を採用するのがよいと思う。@Async 無しでも非同期になるので。

(AsyncController.java)

package com.example.demo;

import java.util.concurrent.CompletableFuture;
import java.util.function.Supplier;
import lombok.RequiredArgsConstructor;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequiredArgsConstructor
public class AsyncController {

  private final IAsyncService anno1Wrap1;
  private final IAsyncService anno0Wrap1;
  private final IAsyncService anno1Wrap0;
  private final IAsyncService anno0Wrap0;

  @RequestMapping("/")
  public String all() {
    var s = "";
    s += process(anno1Wrap1);
    s += process(anno0Wrap1);
    s += process(anno1Wrap0);
    s += process(anno0Wrap0);
    return s;
  }

  private String process(IAsyncService service) {
    var startMs = System.currentTimeMillis();
    var cf1 = service.method1();
    var cf2 = service.method2();
    var cf3 = service.method3();
    var s = "";
    s += cf1.join() + "\n";
    s += cf2.join() + "\n";
    s += cf3.join() + "\n";
    s += lapseMs(startMs) + "ms" + "\n\n";
    return s;
  }

  private long lapseMs(long startMs) {
    return System.currentTimeMillis() - startMs;
  }
}

interface IAsyncService {
  CompletableFuture<String> method1();
  CompletableFuture<String> method2();
  CompletableFuture<String> method3();
}

@Component
class Common {

  public String getClassMethod(Object o) {
    String[] a = o.getClass().getName().split("\\.");
    String className = a[a.length - 1].split("\\$")[0];
    String methodName = o.getClass().getEnclosingMethod().getName();
    return className + "." + methodName + "()";
  }

  public Supplier<String> sleepSupplier(String s) {
    return () -> {
      try {
        Thread.sleep(100);
      } catch (InterruptedException e) {}
      return s;
    };
  }

  public String sleepProcess(String s) {
    try {
      Thread.sleep(100);
    } catch (InterruptedException e) {}
    return s;
  }
}

@Service
@RequiredArgsConstructor
class Anno0Wrap0 implements IAsyncService {

  private final Common common;

  public CompletableFuture<String> method1() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.completedFuture(common.sleepProcess(s));
  }

  public CompletableFuture<String> method2() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.completedFuture(common.sleepProcess(s));
  }

  public CompletableFuture<String> method3() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.completedFuture(common.sleepProcess(s));
  }
}

@Service
@RequiredArgsConstructor
class Anno0Wrap1 implements IAsyncService {

  private final Common common;

  public CompletableFuture<String> method1() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.supplyAsync(common.sleepSupplier(s));
  }

  public CompletableFuture<String> method2() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.supplyAsync(common.sleepSupplier(s));
  }

  public CompletableFuture<String> method3() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.supplyAsync(common.sleepSupplier(s));
  }
}

@Service
@RequiredArgsConstructor
class Anno1Wrap0 implements IAsyncService {

  private final Common common;

  @Async
  public CompletableFuture<String> method1() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.completedFuture(common.sleepProcess(s));
  }

  @Async
  public CompletableFuture<String> method2() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.completedFuture(common.sleepProcess(s));
  }

  @Async
  public CompletableFuture<String> method3() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.completedFuture(common.sleepProcess(s));
  }
}

@Service
@RequiredArgsConstructor
class Anno1Wrap1 implements IAsyncService {

  private final Common common;

  @Async
  public CompletableFuture<String> method1() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.supplyAsync(common.sleepSupplier(s));
  }

  @Async
  public CompletableFuture<String> method2() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.supplyAsync(common.sleepSupplier(s));
  }

  @Async
  public CompletableFuture<String> method3() {
    final String s = common.getClassMethod(new Object() {});
    return CompletableFuture.supplyAsync(common.sleepSupplier(s));
  }
}

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package com.example.demo;

import java.util.concurrent.CompletableFuture;

import java.util.function.Supplier;

import lombok.RequiredArgsConstructor;

import org.springframework.scheduling.annotation.Async;

import org.springframework.stereotype.Component;

import org.springframework.stereotype.Service;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

@RestController

@RequiredArgsConstructor

public class AsyncController {

private final IAsyncService anno1Wrap1;

private final IAsyncService anno0Wrap1;

private final IAsyncService anno1Wrap0;

private final IAsyncService anno0Wrap0;

@RequestMapping("/")

public String all() {

var s = "";

s += process(anno1Wrap1);

s += process(anno0Wrap1);

s += process(anno1Wrap0);

s += process(anno0Wrap0);

return s;

}

private String process(IAsyncService service) {

var startMs = System.currentTimeMillis();

var cf1 = service.method1();

var cf2 = service.method2();

var cf3 = service.method3();

var s = "";

s += cf1.join() + "\n";

s += cf2.join() + "\n";

s += cf3.join() + "\n";

s += lapseMs(startMs) + "ms" + "\n\n";

return s;

}

private long lapseMs(long startMs) {

return System.currentTimeMillis() - startMs;

}

interface IAsyncService {

CompletableFuture<String> method1();

CompletableFuture<String> method2();

CompletableFuture<String> method3();

}

@Component

class Common {

public String getClassMethod(Object o) {

String[] a = o.getClass().getName().split("\\.");

String className = a[a.length - 1].split("\\$")[0];

String methodName = o.getClass().getEnclosingMethod().getName();

return className + "." + methodName + "()";

}

public Supplier<String> sleepSupplier(String s) {

return () -> {

try {

Thread.sleep(100);

} catch (InterruptedException e) {}

return s;

};

}

public String sleepProcess(String s) {

try {

Thread.sleep(100);

} catch (InterruptedException e) {}

return s;

}

@Service

@RequiredArgsConstructor

class Anno0Wrap0 implements IAsyncService {

private final Common common;

public CompletableFuture<String> method1() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.completedFuture(common.sleepProcess(s));

}

public CompletableFuture<String> method2() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.completedFuture(common.sleepProcess(s));

}

public CompletableFuture<String> method3() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.completedFuture(common.sleepProcess(s));

}

@Service

@RequiredArgsConstructor

class Anno0Wrap1 implements IAsyncService {

private final Common common;

public CompletableFuture<String> method1() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.supplyAsync(common.sleepSupplier(s));

}

public CompletableFuture<String> method2() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.supplyAsync(common.sleepSupplier(s));

}

public CompletableFuture<String> method3() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.supplyAsync(common.sleepSupplier(s));

}

@Service

@RequiredArgsConstructor

class Anno1Wrap0 implements IAsyncService {

private final Common common;

@Async

public CompletableFuture<String> method1() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.completedFuture(common.sleepProcess(s));

}

@Async

public CompletableFuture<String> method2() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.completedFuture(common.sleepProcess(s));

}

@Async

public CompletableFuture<String> method3() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.completedFuture(common.sleepProcess(s));

}

@Service

@RequiredArgsConstructor

class Anno1Wrap1 implements IAsyncService {

private final Common common;

@Async

public CompletableFuture<String> method1() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.supplyAsync(common.sleepSupplier(s));

}

@Async

public CompletableFuture<String> method2() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.supplyAsync(common.sleepSupplier(s));

}

@Async

public CompletableFuture<String> method3() {

final String s = common.getClassMethod(new Object() {});

return CompletableFuture.supplyAsync(common.sleepSupplier(s));

}

(DemoApplication.java)

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;

@SpringBootApplication
@EnableAsync
public class DemoApplication {

  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }
}

package com.example.demo;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.scheduling.annotation.EnableAsync;

@SpringBootApplication

@EnableAsync

public class DemoApplication {

public static void main(String[] args) {

SpringApplication.run(DemoApplication.class, args);

}

curl localhost の結果

Anno1Wrap1.method1()
Anno1Wrap1.method2()
Anno1Wrap1.method3()
108ms

Anno0Wrap1.method1()
Anno0Wrap1.method2()
Anno0Wrap1.method3()
101ms

Anno1Wrap0.method1()
Anno1Wrap0.method2()
Anno1Wrap0.method3()
101ms

Anno0Wrap0.method1()
Anno0Wrap0.method2()
Anno0Wrap0.method3()
302ms

Anno1Wrap1.method1()

Anno1Wrap1.method2()

Anno1Wrap1.method3()

108ms

Anno0Wrap1.method1()

Anno0Wrap1.method2()

Anno0Wrap1.method3()

101ms

Anno1Wrap0.method1()

Anno1Wrap0.method2()

Anno1Wrap0.method3()

101ms

Anno0Wrap0.method1()

Anno0Wrap0.method2()

Anno0Wrap0.method3()

302ms

2023.03.26

Javaでstreamのmapの練習

import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        List<String> fruits = Arrays.asList(
            "apple", "kiwi fruit", "strawberry", "orange"
        );
        
        var fruitsUpperCase = fruits.stream()
                .map(e -> e.toUpperCase())
                .collect(Collectors.toList());

        p(fruits);
        p(fruitsUpperCase);
    }
    
    public static <T> void p(T a) {
        System.out.println(a);
    }
}

import java.util.*;

import java.util.stream.*;

public class Main {

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

List<String> fruits = Arrays.asList(

"apple", "kiwi fruit", "strawberry", "orange"

);

var fruitsUpperCase = fruits.stream()

.map(e -> e.toUpperCase())

.collect(Collectors.toList());

p(fruits);

p(fruitsUpperCase);

}

public static <T> void p(T a) {

System.out.println(a);

}

[apple, kiwi fruit, strawberry, orange]
[APPLE, KIWI FRUIT, STRAWBERRY, ORANGE]

1 2	[apple, kiwi fruit, strawberry, orange] [APPLE, KIWI FRUIT, STRAWBERRY, ORANGE]

2023.02.18

Javaのインナークラスの練習

public class Main {
    public static void main(String[] args) throws Exception {
        Flyable bird = FlyableFactory.create();
        bird.fly();
    }
}

interface Flyable {
    public void fly();
}

class FlyableFactory {
    public static Flyable create() {
        return (new FlyableFactory()).new InnerClass();
    }

    private class InnerClass implements Flyable {
        @Override
        public void fly() {
            System.out.println("Flyableインタフェースのflyメソッドです。");
        }
    }
}

public class Main {

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

Flyable bird = FlyableFactory.create();

bird.fly();

}

interface Flyable {

public void fly();

}

class FlyableFactory {

public static Flyable create() {

return (new FlyableFactory()).new InnerClass();

}

private class InnerClass implements Flyable {

@Override

public void fly() {

System.out.println("Flyableインタフェースのflyメソッドです。");

}

Flyableインタフェースのflyメソッドです。

1	Flyableインタフェースのflyメソッドです。

2023.02.05

Javaのジェネリック(ジェネリクス)で配列を扱いたい

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Integer[] numbers = {1, 2, 3, 4, 5};
        Main.<Integer>dispArray(numbers);
    }
    
    public static <T> void dispArray(T[] a) {
        for (int i = 0; i < a.length; i++) {
            p(a[i]);
        }
    }

    public static <T> void p(T a) {
        System.out.println(a);
    }
}

import java.util.*;

public class Main {

public static void main(String[] args) {

Integer[] numbers = {1, 2, 3, 4, 5};

Main.<Integer>dispArray(numbers);

}

public static <T> void dispArray(T[] a) {

for (int i = 0; i < a.length; i++) {

p(a[i]);

}

public static <T> void p(T a) {

System.out.println(a);

}

2023.02.03

Javaのジェネリックメソッドの練習

public class Main {

  public static void main(String[] args) {
    p(onlyReturn("こんにちは！"));
    p(onlyReturn(123));
    p(onlyReturn(new Cat(3)));
  }

  public static <T> void p(T a) {
    System.out.println(a);
  }

  public static <T> T onlyReturn(T a) {
    return a;
  }
}

abstract class Animal {

  protected int age;

  protected Animal(int age) {
    this.age = age;
  }

  abstract String cry();
}

class Cat extends Animal {

  public Cat(int age) {
    super(age);
  }

  @Override
  public String cry() {
    return "にゃー(" + this.age + ")";
  }

  @Override
  public String toString() {
    return this.cry();
  }
}

public class Main {

public static void main(String[] args) {

p(onlyReturn("こんにちは！"));

p(onlyReturn(123));

p(onlyReturn(new Cat(3)));

}

public static <T> void p(T a) {

System.out.println(a);

}

public static <T> T onlyReturn(T a) {

return a;

}

abstract class Animal {

protected int age;

protected Animal(int age) {

this.age = age;

}

abstract String cry();

}

class Cat extends Animal {

public Cat(int age) {

super(age);

}

@Override

public String cry() {

return "にゃー(" + this.age + ")";

}

@Override

public String toString() {

return this.cry();

}

こんにちは！
123
にゃー(3)

こんにちは！

123

にゃー(3)

2022.01.19

Javaのジェネリクスとイテレータの練習

import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        var sub = new Sub();
        sub.run();
    }
}

class Sub {
    public void run() {
        var list = getList();
        p(list);
        
        var iterator = list.iterator();
        while (iterator.hasNext()) {
            var next = iterator.next();
            p(next);
        }
    }
    public <T> void p(T a) {
        System.out.println(a);
    }
    public void p() {
        System.out.println();
    }
    public List getList() {
        var n = 5;
        List<Integer> list = new ArrayList<>();
        for (var i = 0; i < n; i++) {
            list.add(i);
        }
        return list;
    }
}

import java.util.*;

public class Main {

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

var sub = new Sub();

sub.run();

}

class Sub {

public void run() {

var list = getList();

p(list);

var iterator = list.iterator();

while (iterator.hasNext()) {

var next = iterator.next();

p(next);

}

public <T> void p(T a) {

System.out.println(a);

}

public void p() {

System.out.println();

}

public List getList() {

var n = 5;

List<Integer> list = new ArrayList<>();

for (var i = 0; i < n; i++) {

list.add(i);

}

return list;

}

[0, 1, 2, 3, 4]
0
1
2
3
4

[0, 1, 2, 3, 4]

2022.01.19

Javaのリストの型に関する新発見

import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        List<Integer> list = getList();
        // list.add("え"); // error: incompatible types
        list.add(4);
        System.out.println(list);
    }
    
    public static List getList() {
        List<String> list = new ArrayList<>();
        list.add("あ");
        list.add("い");
        list.add("う");
        return list;
    }
}

import java.util.*;

public class Main {

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

List<Integer> list = getList();

// list.add("え"); // error: incompatible types

list.add(4);

System.out.println(list);

}

public static List getList() {

List<String> list = new ArrayList<>();

list.add("あ");

list.add("い");

list.add("う");

return list;

}

[あ, い, う, 4]

1	[あ, い, う, 4]

2021.08.09

Javaの抽象クラスのコンストラクタとオーバーライドの練習

import java.util.*;

public class Main {

  public static void main(String[] args) throws Exception {
    Animal a = new Cat(3);
    a.cry();
    System.out.println(a);
  }
}

abstract class Animal {

  protected int age;

  public Animal(int age) {
    this.age = age;
  }

  public abstract void cry();
}

class Cat extends Animal {

  public Cat(int age) {
    super(age);
  }

  @Override
  public void cry() {
    System.out.println("ニャー(" + this.age + ")");
  }

  @Override
  public String toString() {
    return "猫(" + this.age + ")";
  }
}

import java.util.*;

public class Main {

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

Animal a = new Cat(3);

a.cry();

System.out.println(a);

}

abstract class Animal {

protected int age;

public Animal(int age) {

this.age = age;

}

public abstract void cry();

}

class Cat extends Animal {

public Cat(int age) {

super(age);

}

@Override

public void cry() {

System.out.println("ニャー(" + this.age + ")");

}

@Override

public String toString() {

return "猫(" + this.age + ")";

}

2021.05.02

Javaのジェネリクスとストリームの練習

import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) {
        Sub.main(args);
    }
}

class Sub {
    public static void main(String[] args) {
        List<Animal> animals = new ArrayList<>();
        animals.add(new Cat(3));
        animals.add(new Mike(5));
        animals.add(new Dog(7));
        var breeder = new Breeder();
        breeder.breed(animals);
    }
}

class u {
    public static <T> void pln(T t) {
        System.out.println(t);
    }
    public static <T> void pln() {
        System.out.println();
    }
}

abstract class Animal {
    protected int age;
    protected String voice;
    public Animal(int age) {
        this.age = age;
    }
    public String toString() {
        var str = this.voice + "(" + this.age + ")";
        return str;
    }
    public void cry() {
        System.out.println(this.toString());
    }
}

class Cat extends Animal {
    public Cat(int age) {
        super(age);
        this.voice = "ニャー";
    }
}

class Mike extends Cat {
    public Mike(int age) {
        super(age);
        this.voice = "ミケニャー";
    }
}

class Dog extends Animal {
    public Dog(int age) {
        super(age);
        this.voice = "ワン";
    }
}

class Breeder {
    public void breed(List<Animal> animals) {
        animals.stream().forEach((var animal) -> {
            System.out.println(animal);
        });
    }
}

import java.util.*;

import java.util.stream.*;

public class Main {

public static void main(String[] args) {

Sub.main(args);

}

class Sub {

public static void main(String[] args) {

List<Animal> animals = new ArrayList<>();

animals.add(new Cat(3));

animals.add(new Mike(5));

animals.add(new Dog(7));

var breeder = new Breeder();

breeder.breed(animals);

}

class u {

public static <T> void pln(T t) {

System.out.println(t);

}

public static <T> void pln() {

System.out.println();

}

abstract class Animal {

protected int age;

protected String voice;

public Animal(int age) {

this.age = age;

}

public String toString() {

var str = this.voice + "(" + this.age + ")";

return str;

}

public void cry() {

System.out.println(this.toString());

}

class Cat extends Animal {

public Cat(int age) {

super(age);

this.voice = "ニャー";

}

class Mike extends Cat {

public Mike(int age) {

super(age);

this.voice = "ミケニャー";

}

class Dog extends Animal {

public Dog(int age) {

super(age);

this.voice = "ワン";

}

class Breeder {

public void breed(List<Animal> animals) {

animals.stream().forEach((var animal) -> {

System.out.println(animal);

});

}

ニャー(3)
ミケニャー(5)
ワン(7)

ニャー(3)

ミケニャー(5)

ワン(7)

2021.05.01

DockerでJavaをコンパイルして実行する方法

ホストのMain.javaがあるディレクトリで次のコマンドを実行する。

docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp \
    openjdk:11 bash -c 'javac Main.java; java Main; rm *.class;';

1 2	docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp \ openjdk:11 bash -c 'javac Main.java; java Main; rm *.class;';

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