CompletableFuture demo

CompletableFutureTest.java

public class CompletableFutureTest {

    static class User {
        private String nickname;

        public String getNickname() {
            return nickname;
        }

        public void setNickname(String nickname) {
            this.nickname = nickname;
        }
    }

    public User findUser() {
        return new User();
    }

    private void update(User user) {
        user.setNickname("haha");
        System.out.println("update to db");
    }

    private void es(User user) {
        System.out.println("save to es");
    }

    private void cache(User user) {
        System.out.println("cache ...");
    }
    public void test() throws ExecutionException, InterruptedException {
        CompletableFuture.supplyAsync(this::findUser)
                .thenCompose(user -> {
                    if (user == null) {
                        throw new IllegalArgumentException("userInfoVO error");
                    }
                    return CompletableFuture.supplyAsync(() -> user);
                })
                .exceptionally(ex -> {
                    System.out.println(ex);
                    return null;
                })
                .thenApplyAsync(user -> {
                    System.out.println("thenApplyAsync update");
                    if (user != null) {
                        update(user);
                    }
                    return user;
                })
                .thenApplyAsync(user -> {
                    System.out.println("thenApplyAsync es");
                    if (user != null) {
                        es(user);
                    }
                    return user;
                })
                .thenApplyAsync(user -> {
                    System.out.println("thenApplyAsync cache");
                    if (user != null) {
                        cache(user);
                    }
                    return user;
                }).get();
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        new CompletedFutureTest().test();
    }
  
}