java - Spring @Autowired RestTemplate 为 null

Question

这个问题已经有答案了:

Why is my Spring @Autowired field null? (21 个回答)

已关闭 5 年前。

我是 Spring 新手。我使用 Java 开发使用带证书的 RESTful 服务的服务

这是我的配置类:

package configuration;

import org.apache.http.client.HttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.ssl.SSLContextBuilder;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.util.ResourceUtils;
import org.springframework.web.client.RestTemplate;

import javax.net.ssl.SSLContext;
import java.util.function.Supplier;

@Configuration
public class RestClientCertConfig {

    private char[] allPassword = "allpassword".toCharArray();

    @Bean
    public RestTemplate restTemplate(RestTemplateBuilder builder) throws Exception {

        SSLContext sslContext = SSLContextBuilder
                .create()
                .loadKeyMaterial(ResourceUtils.getFile("classpath:keystore.jks"), allPassword, allPassword)
                .loadTrustMaterial(ResourceUtils.getFile("classpath:truststore.jks"), allPassword)
                .build();

        HttpClient client = HttpClients.custom()
                .setSSLContext(sslContext)
                .build();

        return builder
                .requestFactory((Supplier<ClientHttpRequestFactory>)new HttpComponentsClientHttpRequestFactory(client))
                .build();
    }
}

这是我使用 Restful EndPoint 的类:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.*;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestTemplate;
import java.net.URISyntaxException;
import java.util.Collections;


public class ECSConfigGet {
    private static final String ECS_API_URI = "<RestEndPointToConsume";

    @Autowired
    private static RestTemplate restTemplate;


    public static void main(String[] args) {
        try {
            makeECSCall("myTestHeaderValue");
        } catch (URISyntaxException e) {
            e.printStackTrace();
        }
    }


    private static void makeECSCall(String entityCode) throws RestClientException, URISyntaxException {
        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
        headers.set("entityCode", entityCode);

        HttpEntity<String> entity = new HttpEntity<>("parameters", headers);

        ResponseEntity responseEntity  = restTemplate.exchange(ECS_API_URI, HttpMethod.GET, entity, String.class);
        }
    }

我完全误解了这个概念吗？我希望restTemplate 对于我使用的所有注释都不会为空。感谢您的帮助!

<小时/>

NullPointerException 已修复。 ECSConfigGet 看起来像:

package main;

import configuration.RestClientCertConfig;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.http.*;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestTemplate;
import services.modelsdto.ExpenseConfigDTO;


import java.util.Collections;

@SpringBootApplication
@Component
public class ECSConfigGet implements CommandLineRunner{

    //API to call
    private static final String ECS_API_URI = "<API_TO_CONSUME>";
    @Autowired
    private RestTemplate restTemplate;

    public static void main(String[] args) {

        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(RestClientCertConfig.class);
        applicationContext.getBean(RestTemplate.class);
        SpringApplication.run(ECSConfigGet.class, args);

    }

    private void makeECSCall(String entityCode) throws RestClientException {

        ExpenseConfigDTO expenseConfigDTO = new ExpenseConfigDTO();

        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
        headers.set("entityCode", entityCode);

        HttpEntity<String> entity = new HttpEntity<>("parameters", headers);

        ResponseEntity responseEntity  = restTemplate.exchange(ECS_API_URI, HttpMethod.GET, entity, String.class);
        }

    @Override
    public void run(String... args) {
        for (int i = 0; i < args.length; ++i) {
            makeECSCall("myTestHeaderValue");
        }
    }
}

Answer 1

您缺少一些使 @Autowired 工作所需的 Spring 样板文件。如果您使用 Spring Boot，那么您已经很接近了，但 @Patrick 通常是正确的:ECSConfigGet 需要通过正确注释来成为一个 bean，但您还需要在应用程序上下文中运行应用程序为了让任何 Spring 的魔法发生。我建议查看this tutorial了解如何在命令行应用程序中使用 Spring Boot。

高层是ECSConfigGet需要用@SpringBootApplication注释，然后让它实现CommandLineRunner，然后从运行 方法，您将可以访问 @Autowired 组件。 Spring 将实例化 ECSConfigGet 并填充属性。另外，正如 @Roddy 指出的，RestTemplate 也不能是静态的。