java - 使用 Spring Boot 从命令行接收输入

Question

所以我有一个非常小的 Spring Boot 命令行应用程序(没有嵌入式 tomcat 服务器或任何使其成为 Web 应用程序的东西)，其中有一个类，我尝试使用 Scanner 类从 java.util 读取用户的输入。这根本不起作用。我认为这在 Spring Boot 中是非常基本的东西，但我在 S.O 或教程上的所有搜索都没有产生任何结果。最好的方法是什么？还是 Spring Boot 不适合我想做的事情？

这是我的类(class):

package test;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.util.Scanner;

@SpringBootApplication
public class MyApplication implements CommandLineRunner {

    private static Logger LOG = LoggerFactory
        .getLogger(MyApplication.class);

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(MyApplication.class);
        app.run(args);
    }

    @Override
    public void run(String... args) throws Exception {
        LOG.info("EXECUTING : command line runner");

        Scanner in = new Scanner(System.in);

        System.out.println("What is your name?");
        String name = in.next();
        System.out.println("Hello " + name + " welcome to spring boot" );
    }
}

抛出的异常是:

2019-05-29 11:31:29.116  INFO 4321 --- [           main] test.MyApplication  : EXECUTING : command line runner
2019-05-29 11:31:29.119  INFO 4321 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-05-29 11:31:29.124 ERROR 4321 --- [           main] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalStateException: Failed to execute CommandLineRunner
        at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:816) ~[spring-boot-2.1.5.RELEASE.jar:2.1.5.RELEASE]
        at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:797) ~[spring-boot-2.1.5.RELEASE.jar:2.1.5.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:324) ~[spring-boot-2.1.5.RELEASE.jar:2.1.5.RELEASE]
        at com.jaletechs.png.PrimeNumberGeneratorApplication.main(MyApplication.java:19) [main/:na]
Caused by: java.util.NoSuchElementException: null
        at java.util.Scanner.throwFor(Scanner.java:862) ~[na:1.8.0_201]
        at java.util.Scanner.next(Scanner.java:1371) ~[na:1.8.0_201]
        at test.MyApplication.run(MyApplication.java:27) [main/:na]
        at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:813) ~[spring-boot-2.1.5.RELEASE.jar:2.1.5.RELEASE]
        ... 3 common frames omitted

Answer 1

我遵循以下方法，

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

@Component
public class MyRunner implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        System.out.println("Enter word!");
        Scanner scanner = new Scanner(System.in);
        String line = scanner.nextLine();
        System.out.println(line);
     }
}

它对我来说效果很好，你也可以在主类中组合命令行监听器。