如何使用注释自动连接 RestTemplate

当我尝试自动连接 Spring RestTemplate 时，出现以下错误:

nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.web.client.RestTemplate] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency.

在注释驱动的环境中使用 Spring4。

我的调度器 servlet 配置如下:

<context:component-scan base-package="in.myproject" />
<mvc:default-servlet-handler />
<mvc:annotation-driven />
<bean id="restTemplate" class="org.springframework.web.client.RestTemplate"/>

我试图自动连接 RestTemplate 的类如下:

@Service("httpService")
public class HttpServiceImpl implements HttpService {


@Autowired
private RestTemplate restTemplate;


@Override
public void sendUserId(String userId){


MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
map.add("userId", userId);
map.add("secretKey", "kbhyutu7576465duyfy");


restTemplate.postForObject("http://localhost:8081/api/user", map, null);




}
}
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小开 
@Autowired
private RestOperations restTemplate;

You can only autowire interfaces with implementations.

小开

If you're using Spring Boot 1.4.0 or later as the basis of your annotation-driven, Spring doesn't provides a single auto-configured RestTemplate bean. From their documentation:

https://docs.spring.io/spring-boot/docs/1.4.0.RELEASE/reference/html/boot-features-restclient.html

If you need to call remote REST services from your application, you can use Spring Framework’s RestTemplate class. Since RestTemplate instances often need to be customized before being used, Spring Boot does not provide any single auto-configured RestTemplate bean. It does, however, auto-configure a RestTemplateBuilder which can be used to create RestTemplate instances when needed. The auto-configured RestTemplateBuilder will ensure that sensible HttpMessageConverters are applied to RestTemplate instances.

小开

You can add the method below to your class for providing a default implementation of RestTemplate:

@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
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Errors you'll see if a RestTemplate isn't defined

Consider defining a bean of type 'org.springframework.web.client.RestTemplate' in your configuration.

or

No qualifying bean of type [org.springframework.web.client.RestTemplate] found

How to define a RestTemplate via annotations

Depending on which technologies you're using and what versions will influence how you define a RestTemplate in your @Configuration class.

Spring >= 4 without Spring Boot

Simply define an @Bean:

@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}

Spring Boot <= 1.3

No need to define one, Spring Boot automatically defines one for you.

Spring Boot >= 1.4

Spring Boot no longer automatically defines a RestTemplate but instead defines a RestTemplateBuilder allowing you more control over the RestTemplate that gets created. You can inject the RestTemplateBuilder as an argument in your @Bean method to create a RestTemplate:

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
// Do any additional configuration here
return builder.build();
}

Using it in your class

@Autowired
private RestTemplate restTemplate;

or 

@Inject
private RestTemplate restTemplate;
小开 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;


@Configuration
public class RestTemplateClient {
@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
小开

Add the @Configuration annotation in the RestTemplateSOMENAME which extends the RestTemplate class.

@Configuration
public class RestTemplateClass extends RestTemplate {


}

Then in your controller class you can use the Autowired annotation as follows.

@Autowired
RestTemplateClass restTemplate;

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