Could not autowire field:RestTemplate in Spring boot application

If a TestRestTemplate is a valid option in your unit test, this documentation might be relevant

http://docs.spring.io/spring-boot/docs/1.4.1.RELEASE/reference/htmlsingle/#boot-features-rest-templates-test-utility

Short answer: if using

@SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)

then @Autowired will work. If using

@SpringBootTest(webEnvironment=WebEnvironment.MOCK)

then create a TestRestTemplate like this

private TestRestTemplate template = new TestRestTemplate();

This will help to avoid creation of a RestTemplate that wouldn't be used outside tests.

You must add

@Bean 
public RestTemplate restTemplate(RestTemplateBuilder builder){
  return builder.build();
}

you are trying to inject the restTemplate but you need to create configuration class . then there you need to create bean that return you new RestTemplate see the below example.

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;


@Configuration
public class YourConfigClass {


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

}

Since RestTemplate instances often need to be customized before being used, Spring Boot does not provide any single auto-configured RestTemplate bean.

RestTemplateBuilder offers proper way to configure and instantiate the rest template bean, for example for basic auth or interceptors.

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
    return builder
            .basicAuthorization("user", "name") // Optional Basic auth example
            .interceptors(new MyCustomInterceptor()) // Optional Custom interceptors, etc..
            .build();
}

Please make sure two things:

1- Use @Bean annotation with the method.

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder){
    return builder.build();
}

2- Scope of this method should be public not private.

Complete Example -

@Service
public class MakeHttpsCallImpl implements MakeHttpsCall {

@Autowired
private RestTemplate restTemplate;

@Override
public String makeHttpsCall() {
    return restTemplate.getForObject("https://localhost:8085/onewayssl/v1/test",String.class);
}

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder){
    return builder.build();
}
}

The simplest way I was able to achieve a similar feat to use the code below (reference), but I would suggest not to make API calls in controllers(SOLID principles). Also autowiring this way is better optimsed than the traditional way of doing it.

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class TestController {

    private final RestTemplate restTemplate;


    @Autowired
    public TestController(RestTemplateBuilder builder) {
        this.restTemplate = builder.build();
    }

    @RequestMapping(value="/micro/order/{id}", method= RequestMethod.GET, produces= MediaType.ALL_VALUE)
    public String placeOrder(@PathVariable("id") int customerId){

        System.out.println("Hit ===> PlaceOrder");

        Object[] customerJson = restTemplate.getForObject("http://localhost:8080/micro/customers", Object[].class);

        System.out.println(customerJson.toString());

        return "false";
    }
}

Error points directly that RestTemplate bean is not defined in context and it cannot load the beans.

1. Define a bean for RestTemplate and then use it
2. Use a new instance of the RestTemplate

If you are sure that the bean is defined for the RestTemplate then use the following to print the beans that are available in the context loaded by spring boot application

ApplicationContext ctx = SpringApplication.run(Application.class, args);
String[] beanNames = ctx.getBeanDefinitionNames();
Arrays.sort(beanNames);
for (String beanName : beanNames) {
    System.out.println(beanName);
}

If this contains the bean by the name/type given, then all good. Or else define a new bean and then use it.

This error usually happens when Spring Boot cannot find or create the RestTemplateBuilder bean automatically. if you are in reactive web, you have to define a new one manually. The most common causes and fixes are as follows:

Missing Spring Boot Web dependency

RestTemplateBuilder is auto-configured only when you have Spring Web or Spring WebFlux dependencies. Check your pom.xml or build.gradle for these:

Maven

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

If you are using WebFlux, then add:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

Add a RestTemplate Bean

If you want to use RestTemplate, define it as a bean using the RestTemplateBuilder:

import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate(RestTemplateBuilder builder) {
        return builder.build();
    }
}

Using RestTemplateBuilder directly

If Spring Boot still doesn't find the RestTemplateBuilder, manually declare it:

@Bean
public RestTemplateBuilder restTemplateBuilder() {
    return new RestTemplateBuilder();
}

But normally, you shouldn't need this if spring-boot-starter-web is present.

Verify Spring Boot version

• RestTemplateBuilder is available in Spring Boot 1.4+.
• If you’re on older Spring Boot, consider upgrading.

For Spring WebFlux projects

If you are using Spring WebFlux, prefer WebClient over RestTemplate, as RestTemplate is blocking and WebFlux is reactive:

@Bean
public WebClient.Builder webClientBuilder() {
    return WebClient.builder();
}