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https://github.com/gocardless/gocardless-pro-java

GoCardless Pro Java Client
https://github.com/gocardless/gocardless-pro-java

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GoCardless Pro Java Client

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README 

        
# Java Client for GoCardless Pro API



This library provides a simple wrapper around the [GoCardless API](http://developer.gocardless.com/api-reference).



- ["Getting started" guide](https://developer.gocardless.com/getting-started/api/introduction/?lang=java) with copy and paste Java code samples

- [API Reference](https://developer.gocardless.com/api-reference/2015-07-06)

- [Example application](https://github.com/gocardless/gocardless-pro-java-example)



## Getting started



With Maven:



```xml



    com.gocardless

    gocardless-pro

    6.6.0



```



With Gradle:



```

implementation 'com.gocardless:gocardless-pro:6.6.0'

```



## Initializing the client



The client is initialised with an access token, and is configured to use GoCardless' live environment by default:



```java

import com.gocardless.GoCardlessClient;



String accessToken = "AO00000123";



GoCardlessClient client = GoCardlessClient.newBuilder(accessToken).build();

```



Optionally, the client can be customised with an environment, base URL, proxy and/or SSL socket factory, custom no of retries,

wait time between retries by calling `.withX` methods on the `Builder`, max no of allowed retries are 3 :



```java

import com.gocardless.GoCardlessClient;

import java.net.InetSocketAddress;

import java.net.Proxy;



String accessToken = "AO00000123";

Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("127.0.0.1", 8080));



GoCardlessClient client = GoCardlessClient.newBuilder(accessToken)

    .withEnvironment(GoCardlessClient.Environment.SANDBOX)

    .withMaxNoOfRetries(2)

    .withWaitBetweenRetriesInMilliSeconds(200)

    .withProxy(proxy)

    .build();

```



To see the configurable options in full, see the documentation for `GoCardlessClient.Builder`.



If you're upgrading from v2.x, you'll need to update your code for initialising `GoCardlessClient`. See the

"Upgrading from v2.x to v3.x or above" section below.



## Examples



### Fetching resources



To fetch a single item, use the `get` method:



```java

Mandate mandate = client.mandates().get("MD123").execute();

System.out.println(mandate.getReference());

```



### Listing resources



To fetch items in a collection, there are two options:



* Fetching items one page at a time:



```java

ListResponse firstPage = client.customers().list().execute();

for (Customer customer : firstPage.getItems()) {

    System.out.println(customer.getGivenName());

}



String cursor = firstPage.getAfter();

ListResponse nextPage = client.customers().list().withAfter(cursor).execute();

```



* Iterating through all of the items in a collection:



```java

for (Customer customer : client.customers().all().execute()) {

    System.out.println(customer.getGivenName());

}

```



### Creating resources



Resources can be created with the `create` method:



```java

Creditor creditor = client.creditors().create()

    .withName("The Wine Club")

    .withAddressLine1("9 Acer Gardens")

    .withCity("Birmingham")

    .withPostalCode("B4 7NJ")

    .withCountryCode("GB")

    .execute();

```



### Updating resources



Resources can be updates with the `update` method:



```java

Subscription subscription = client.subscriptions().update("SU123")

    .withName("New name")

    .execute();

```



### Retrying requests



The library will attempt to retry most failing requests automatically (with the exception

of those which are not safe to retry).



`GET` requests are considered safe to retry, and will be retried automatically. Certain

`POST` requests are made safe to retry by the use of an idempotency key, generated

automatically by the library, so we'll automatically retry these too.



If you want to override this behaviour

(for example, to provide your own retry mechanism), then you can use the `executeWrapped`

method in place of `execute`.  This returns an `ApiResponse` object, which also gives

access to the response status code and headers.



### Setting custom headers



You shouldn't generally need to customise the headers sent by the library, but you wish to

in some cases (for example if you want to send an `Accept-Language` header when

[creating a mandate PDF](https://developer.gocardless.com/api-reference/#mandate-pdfs-create-a-mandate-pdf)).



To do this, the library's request objects have a

`withHeader(String headerName, String headerValue)` method which you can chain before you

call `execute()` to actually make the request:



```java

MandatePdf mandatePdf = client.mandatePdfs.create()

  .withIban("FR14BARC20000055779911")

  .withHeader("Accept-Language", "fr-FR")

  .execute();

```



Custom headers you specify will override any headers generated by the library itself (for

example, an `Authorization` header with your configured access token or an

`Idempotency-Key` header with a randomly-generated value or one you've configured

manually). Custom headers always take precedence.



When you use the `execute()` method to create a resource, if your idempotency key has

already been used, we'll automatically fetch the already-created resource from the API

using the same headers, and will return it to you.



### Handling errors



Any errors will result in a `GoCardlessException` being thrown.  If the error is due to an error response from the API, then an appropriate subclass of `GoCardlessApiException` will be thrown, providing more information about the nature of the error.  This will be one of:



* GoCardlessInternalException

* InvalidApiUsageException

* InvalidStateException

* ValidationFailedException



See the [documentation](http://gocardless.github.io/gocardless-pro-java/com/gocardless/errors/package-summary.html) for more details.



### Handling webhooks



GoCardless supports webhooks, allowing you to receive real-time notifications when things happen in your account, so you can take automatic actions in response, for example:



* When a customer cancels their mandate with the bank, suspend their club membership

* When a payment fails due to lack of funds, mark their invoice as unpaid

* When a customer’s subscription generates a new payment, log it in their “past payments” list



The client allows you to validate that a webhook you receive is genuinely from GoCardless, and to parse it into `com.gocardless.resources.Event` objects which are easy to work with:



```java

package myintegration;



// Use the POM file at

// https://raw.githubusercontent.com/gocardless/gocardless-pro-java-maven-example/master/pom.xml



import java.util.List;

import com.gocardless.Webhook;

import com.gocardless.errors.InvalidSignatureException;

import com.gocardless.resources.Event;

import org.springframework.http.HttpStatus;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.bind.annotation.PostMapping;

import org.springframework.web.bind.annotation.RequestBody;

import org.springframework.web.bind.annotation.RequestHeader;

import org.springframework.http.ResponseEntity;



public class WebhookHandler {

    @PostMapping("/")

    public ResponseEntity handlePost(

            @RequestHeader("Webhook-Signature") String signatureHeader,

            @RequestBody String requestBody) {

        /*

         * When you create a webhook endpoint, you can specify a secret. When GoCardless

         * sends you a webhook, it'll sign the body using that secret. Since only you and

         * GoCardless know the secret, you can check the signature and ensure that the

         * webhook is truly from GoCardless.

         *

         * We recommend storing your webhook endpoint secret in an environment variable

         * for security, but you could include it as a string directly in your code.

         */

        String webhookEndpointSecret = System.getenv("GOCARDLESS_WEBHOOK_ENDPOINT_SECRET");



        try {

            List events = Webhook.parse(requestBody, signatureHeader, webhookEndpointSecret);



            // Work through your list of events...



            return new ResponseEntity("OK", HttpStatus.OK);

        } catch(InvalidSignatureException e) {

            return new ResponseEntity("Incorrect Signature", HttpStatus.BAD_REQUEST);

        }

    }

}

```



For more details on working with webhooks, see our ["Getting started" guide](https://developer.gocardless.com/getting-started/api/introduction/?lang=java).



## Upgrading from v4.x to v5.x or above



### Breaking Changes



- Stop support for apps using Java 7, supports apps using only Java 8 and above

- Response Header names are all in lower case now

- GoCardless client initiation method `withsslSocketFactory` replaced with `withSslSocketFactoryAndTrustManager`



```java

import com.gocardless.GoCardlessClient;

import javax.net.ssl.SSLSocketFactory;

import javax.net.ssl.TrustManager;

import javax.net.ssl.TrustManagerFactory;

import javax.net.ssl.X509TrustManager;

import java.security.KeyStore;



String accessToken = "AO00000123";

TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(

TrustManagerFactory.getDefaultAlgorithm());

trustManagerFactory.init((KeyStore) null);

TrustManager[] trustManagers = trustManagerFactory.getTrustManagers();

if (trustManagers.length != 1 || !(trustManagers[0] instanceof X509TrustManager)) {

    throw new IllegalStateException("Unexpected default trust managers:"

        + Arrays.toString(trustManagers));

}

X509TrustManager trustManager = (X509TrustManager) trustManagers[0];



SSLContext sslContext = SSLContext.getInstance("TLS");

sslContext.init(null, new TrustManager[] { trustManager }, null);

SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();



GoCardlessClient client = GoCardlessClient.newBuilder(accessToken)

    .withSslSocketFactoryAndTrustManager(sslSocketFactory, trustManager)

    .build();

```



## Upgrading from v2.x to v3.x or above



To upgrade from v2.x, you will need to switch from calling `GoCardlessClient.create` with arguments to

using the `Builder` returned by `GoCardlessClient.newBuilder()` and its `withX()` and `build()` methods.



If you're only setting an access token and using the default GoCardless environment (live):



```java

import com.gocardless.GoCardlessClient;



String accessToken = "foo";



// Before

GoCardlessClient client = GoCardlessClient.create(accessToken)



// After

GoCardlessClient client = GoCardlessClient.newBuilder(accessToken).build();

```



If you're customising the environment as well:



```java

import com.gocardless.GoCardlessClient;



String accessToken = "foo";



// Before

GoCardlessClient client = GoCardlessClient.create(accessToken, GoCardlessClient.Environment.SANDBOX)



// After

GoCardlessClient client = GoCardlessClient.newBuilder(accessToken)

    .withEnvironment(GoCardlessClient.Environment.SANDBOX)

    .build();

```



Or, if you're customising the base URL:



```java

import com.gocardless.GoCardlessClient;



String accessToken = "foo";

String baseUrl = "https://api.gocardless.com";



// Before

GoCardlessClient client = GoCardlessClient.create(accessToken, baseUrl)



// After

GoCardlessClient client = GoCardlessClient.newBuilder(accessToken)

    .withBaseUrl(baseUrl)

    .build();

```



If you were instantiating your own `com.gocardless.http.HttpClient` (which is very unlikely unless you

were patching the internals of the library), you'll now need to supply an `OkHttpClient` as well as the

access token and base URL.



```java

String accessToken = "foo";

String baseUrl = "https://api.gocardless.com";



// Before

HttpClient rawClient = new HttpClient(accessToken, baseUrl);



// After

HttpClient rawClient = new HttpClient(accessToken, baseUrl, new OkHttpClient());

```



Once you've instantiated the client, everything works exactly the same as before, so you won't need to

change any of your other code.



## Compatibility



This library requires JDK version 8 or above.



## Logging



All requests are logged at `INFO` level using [SLF4J](http://www.slf4j.org/).  Logs will only be sent if you have an SLF4J binding on your classpath - we recommend using [Logback](http://logback.qos.ch/).



## Documentation



Full Javadoc can be found [here](http://gocardless.github.io/gocardless-pro-java/com/gocardless/package-summary.html).



## Contributing



This client is auto-generated from Crank, a toolchain that we hope to soon open source. Issues should for now be reported on this repository.  __Please do not modify the source code yourself, your changes will be overridden!__