Java – Get list of JSON objects with Spring RestTemplate

javaresttemplatespring

I have two questions:

How to map a list of JSON objects using Spring RestTemplate.
How to map nested JSON objects.

I am trying to consume https://bitpay.com/api/rates, by following the tutorial from http://spring.io/guides/gs/consuming-rest/.

Best Answer

First define an object to hold the entity coming back in the array.. e.g.

@JsonIgnoreProperties(ignoreUnknown = true)
public class Rate {
    private String name;
    private String code;
    private Double rate;
    // add getters and setters
}

Then you can consume the service and get a strongly typed list via:

ResponseEntity<List<Rate>> rateResponse =
        restTemplate.exchange("https://bitpay.com/api/rates",
                    HttpMethod.GET, null, new ParameterizedTypeReference<List<Rate>>() {
            });
List<Rate> rates = rateResponse.getBody();

The other solutions above will also work, but I like getting a strongly typed list back instead of an Object[].

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Spring – Disabling SSL Certificate Validation in Spring RestTemplate

@Bean
public RestTemplate restTemplate() 
                throws KeyStoreException, NoSuchAlgorithmException, KeyManagementException {
    TrustStrategy acceptingTrustStrategy = (X509Certificate[] chain, String authType) -> true;

    SSLContext sslContext = org.apache.http.ssl.SSLContexts.custom()
                    .loadTrustMaterial(null, acceptingTrustStrategy)
                    .build();

    SSLConnectionSocketFactory csf = new SSLConnectionSocketFactory(sslContext);

    CloseableHttpClient httpClient = HttpClients.custom()
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                    .build();

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    RestTemplate restTemplate = new RestTemplate(requestFactory);
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 }

Java – JsonMappingException: No suitable constructor found for type [simple type, class ]: can not instantiate from JSON object

So, finally I realized what the problem is. It is not a Jackson configuration issue as I doubted.

Actually the problem was in ApplesDO Class:

public class ApplesDO {

    private String apple;

    public String getApple() {
        return apple;
    }

    public void setApple(String apple) {
        this.apple = apple;
    }

    public ApplesDO(CustomType custom) {
        //constructor Code
    }
}

There was a custom constructor defined for the class making it the default constructor. Introducing a dummy constructor has made the error to go away:

public class ApplesDO {

    private String apple;

    public String getApple() {
        return apple;
    }

    public void setApple(String apple) {
        this.apple = apple;
    }

    public ApplesDO(CustomType custom) {
        //constructor Code
    }

    //Introducing the dummy constructor
    public ApplesDO() {
    }

}

Best Answer

Related Solutions

Spring – Disabling SSL Certificate Validation in Spring RestTemplate

Java – JsonMappingException: No suitable constructor found for type [simple type, class ]: can not instantiate from JSON object

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