如何在Spring应用程序输入数据后调用CommandLineRunner

Question

我有一个Spring应用程序，其中我创建了一个POST方法，期望用户通过输入一些信息。一旦获取输入，我将生成一个表示最终URL的字符串。然后，我想在包含CommandLineRunner的Configuration中传递这个字符串URL。

问题是CommandLineRunner在应用程序启动时被执行，这意味着我的输入有空值，因此抛出了null指针异常。是否有可能在应用程序启动后为我的CommandLineRunner添加数据，而不知何故，后者的执行变得平滑？

REST控制器类

package com.andrekreou.covid.gov.controller;

import com.andrekreou.covid.gov.model.Covid;
import com.andrekreou.covid.gov.model.Date;
import com.andrekreou.covid.gov.service.Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class Controller {

    private final Service service;

    @Autowired
    public Controller(Service service) {
        this.service = service;
    }

    @GetMapping(path = "/covid")
    public List<List<Covid>> getData(){
        return service.getData();
    }

    @PostMapping(value = "/insert/date")
    public String insertDate(@ModelAttribute("date") Date date) {
        String inserted_date = date.getDate();
        return "https://data.gov.gr/api/v1/query/mdg_emvolio?date_from=" + inserted_date + "&date_to=" + inserted_date;
    }
}

配置类

package com.andrekreou.covid.gov.configuration;

import com.andrekreou.covid.gov.controller.Controller;
import com.andrekreou.covid.gov.model.Covid;
import com.andrekreou.covid.gov.model.Date;
import com.andrekreou.covid.gov.repository.CovidRepo;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.*;
import org.springframework.web.client.RestTemplate;

import java.util.Collections;
import java.util.List;

@Configuration
public class CovidConfig {

    Controller controller;

    Date date;

    @Bean
    CommandLineRunner commandLineRunner(CovidRepo covidRepo){
        return args -> {

            String url = controller.insertDate(date);
            RestTemplate restTemplate = new RestTemplate();

            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_JSON);
            headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
            headers.set("Authorization","Token 8329eb4fa30e567d9e3f6bfed266c8cb4c9c94ad");

            HttpEntity<Object> request = new HttpEntity<>(headers);

            ResponseEntity<List<Covid>> postEntity = restTemplate.exchange(
                    url,
                    HttpMethod.GET,
                    request,
                    new ParameterizedTypeReference<>() {
                    });

            List<Covid> covidList = postEntity.getBody();
            assert covidList != null;
            covidRepo.saveAll(covidList);
            System.out.println(covidList);
        };
    }
}

POJO类

package com.andrekreou.covid.gov.model;

public class Date {

    private String date;

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }
}

HTML

<html lang="en">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <meta name="description" content="">
    <meta name="author" content="">
    <title>login</title>
    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" rel="stylesheet"
          integrity="sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M" crossorigin="anonymous">
    <link href="https://getbootstrap.com/docs/4.0/examples/signin/signin.css" rel="stylesheet" crossorigin="anonymous">
    <style>
        body {
            background-color: #3e3e3e;
            color: white;
        }
        h2 {
            text-align: center;
        }
    </style>
</head>

<body>
<div class="container">
    <form class="date" name="date" method="post" action="/insert/date" enctype="application/x-www-form-urlencoded">
        <h2 class="form-register-heading">Please Enter Date</h2>
        <p>
            <label for="date" class="sr-only">Date</label>
            <input type="text" id="date" name="date" class="date" placeholder="date" required=""
                   autofocus="">
        </p>
        <button class="btn btn-lg btn-primary btn-block" type="submit">Insert Date</button>
    </form>
</div>
</body>
</html>

Answer 1

这个问题有点奇怪。正如您所说的，当我们使用命令行运行应用程序(因此称为CommandLineRunner)时调用这个功能接口，那时我们可以从命令提示符中给出一些类似于java -jar MyApp "param1" "param2"的参数。param1和param2作为params传递给主方法。因此，它只被称为一次。

CommandLineRunner是一个带有run方法的简单Spring接口。Spring将在应用程序上下文为已加载之后自动调用实现此接口的所有been的run方法。

PS:如果您想在方法完成后调用您的业务逻辑，您可以使用Spring。如果您有另一个场景，比如在另一个线程中执行一个方法，可以使用ExecutorServices类来达到它，或者您可以自己实现它。