# Overview & Structure

The SDK is heavily based on the [builder](https://en.wikipedia.org/wiki/Builder_pattern) and [factory](https://en.wikipedia.org/wiki/Factory_\(object-oriented_programming\)) pattern to create the configuration, service instances and subsequently the objects wrapping the transaction to interact with the aeternity network.

## SDK Service Entrypoint

The central access point to all services is made available through the [AeternityService](https://github.com/kryptokrauts/aepp-sdk-java/blob/master/src/main/java/com/kryptokrauts/aeternity/sdk/service/aeternity/impl/AeternityService.java) which can be obtained via the [AeternityServiceFactory](https://github.com/kryptokrauts/aepp-sdk-java/blob/master/src/main/java/com/kryptokrauts/aeternity/sdk/service/aeternity/AeternityServiceFactory.java). Necessary parameters to f.e. identify the network to use or the endpoints to act against, are defined via the [AeternityServiceConfiguration](https://github.com/kryptokrauts/aepp-sdk-java/blob/master/src/main/java/com/kryptokrauts/aeternity/sdk/service/aeternity/AeternityServiceConfiguration.java). Within this class, the following parameters can be set

| Parameter       | Description                                                                                                                             | Value / Default                                                                                                                                                       |
| --------------- | --------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| baseUrl         | endpoint URL of the aeternity node                                                                                                      | [https://sdk-testnet.aepps.com](https://testnet.aeternity.io)                                                                                                         |
| compilerBaseUrl | endpoint URL of the sophia compiler node                                                                                                | [https://compiler.aepps.com](https://compiler.aeternity.io)                                                                                                           |
| mdwBaseUrl      | endpoint URL of the aeternal middleware                                                                                                 | <https://testnet.aeternity.io/mdw>                                                                                                                                    |
| network         | network to run against - must be considered together with chosen Endpoint URLs                                                          | one of [Network](https://github.com/kryptokrauts/aepp-sdk-java/blob/master/src/main/java/com/kryptokrauts/aeternity/sdk/constants/Network.java)                       |
| nativeMode      | for debug and test purposes - if true, the SDK creates the unsigned transaction from the given model, otherwise the node is called      | true                                                                                                                                                                  |
| baseKeyPair     | the account which is internally used to sign all transactions (if no other  private key is passed in the post transaction method)       | instance of [BaseKeyPair](https://github.com/kryptokrauts/aepp-sdk-java/blob/master/src/main/java/com/kryptokrauts/aeternity/sdk/domain/secret/impl/BaseKeyPair.java) |
| vertx           | the vertx instance which is used within the SDK to call the node interfaces - will be instantiated automatically                        |                                                                                                                                                                       |
| targetVM        | target VM version - depending on the selected VM, contract related transactions need to specify the respective abiVersion and vmVersion | FATE, one of [VirtualMachine](https://github.com/kryptokrauts/aepp-sdk-java/blob/master/src/main/java/com/kryptokrauts/aeternity/sdk/constants/VirtualMachine.java)   |

To actually construct the service configuration and get an instance of the AeternityService, the following steps are necessary. In this example we use a randomly created base key pair

```
KeyPairService keyPairService = new KeyPairServiceFactory().getService();
BaseKeyPair baseKeyPair = keyPairService.generateBaseKeyPair();
AeternityService aeternityService =
        new AeternityServiceFactory()
            .getService(
                AeternityServiceConfiguration.configure()
                    .baseUrl(<baseURL>)
                    .compilerBaseUrl(<compilerBaseUrl>)
                    .aeternalBaseUrl(<aeternalBaseUrl>)
                    .network(Network.<network>)                    
                    .baseKeyPair(baseKeyPair)
                    .targetVM(VirtualMachine.FATE)
                    .compile());
```

## Aeternity Service Capabilities

All provided functions are classified into their purpose for better organization - those will be discussed in the subsequent chapters.

### accounts

### aeternal

### compiler

### info

### names

### oracles

### transactions