Error while consuming a REST API in Spring Boot

Question

I am trying to consume REST API which takes JSON payload and returns plain/text in the response. But I am getting following error during runtime.

SpotifyIntegrationApplication.java

@SpringBootApplication
public class SpotifyIntegrationApplication {

    private static final Logger LOGGER = LoggerFactory.getLogger(SpotifyIntegrationApplication.class);

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

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

    @Bean
    public CommandLineRunner run(RestTemplate restTemplate) {
        NewOrder newOrder = new NewOrder();
        return args -> {
            ResponseEntity<String> responseEntity = restTemplate.postForEntity("http://localhost:9999/order-sold", newOrder, String.class);
            LOGGER.info("responseEntity: " + responseEntity);
        };
    }

}

NewOrder.java

public class NewOrder {
    String orderId;
}

build.gradle

buildscript {
    ext {
        springBootVersion = '1.5.10.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

group = 'com.synapse.integration'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
    mavenCentral()
}


dependencies {
    compile('org.springframework.boot:spring-boot-starter-web')
    runtime('com.h2database:h2')
    runtime('mysql:mysql-connector-java')
    compileOnly('org.projectlombok:lombok')
    testCompile('org.springframework.boot:spring-boot-starter-test')
}

Error:

java.lang.IllegalStateException: Failed to execute CommandLineRunner
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:735) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:716) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:703) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:304) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    at com.synapse.integration.spotify.SpotifyIntegrationApplication.main(SpotifyIntegrationApplication.java:20) [classes/:na]
Caused by: org.springframework.web.client.RestClientException: Could not write request: no suitable HttpMessageConverter found for request type [com.synapse.integration.spotify.model.NewOrder]
    at org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:907) ~[spring-web-4.3.14.RELEASE.jar:4.3.14.RELEASE]
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:658) ~[spring-web-4.3.14.RELEASE.jar:4.3.14.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:621) ~[spring-web-4.3.14.RELEASE.jar:4.3.14.RELEASE]
    at org.springframework.web.client.RestTemplate.postForEntity(RestTemplate.java:415) ~[spring-web-4.3.14.RELEASE.jar:4.3.14.RELEASE]
    at com.synapse.integration.spotify.SpotifyIntegrationApplication.lambda$run$0(SpotifyIntegrationApplication.java:32) [classes/:na]
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:732) [spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
    ... 6 common frames omitted

Answer 1

 I have used restTemplate.exchange but you can modify to use postForEntity 
 or postForObject. Hope this helps.

 private HttpHeaders createHttpHeaders() {
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_JSON);
    return headers;
    }

@RequestMapping("/testClient")
public String testClient() {
    RestTemplate restTemplate = new RestTemplate();
    HttpHeaders headers = createHttpHeaders();
    HttpEntity<String> entity = new HttpEntity<String>("parameters",
            headers);
    ResponseEntity<String> response = restTemplate.exchange(url,
            HttpMethod.GET, entity, String.class);
    if (response.getStatusCode().equals(HttpStatus.OK)) {
        System.out.println("getbody -" + response.getBody());
    }
    return "Test Client";
}