Android library for generating request object and response object from server endpoint definition using annotation processing.

• Eliminates the need to write boilerplate code for network requests and responses.
• Request object is generated based on endpoint definition.
• Response object is generated from json example in the endpoint definition.

#Get started

...
buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        ...
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.6'
    }
}
...

This adds a dependency for com.neenbedankt.gradle.plugins:android-apt plug-in that is required to run Potato library's annotation processor.

apply plugin: 'com.neenbedankt.android-apt'
...
dependencies {
    compile 'com.beastpotato.potato:potato_api:2.8'
    apt 'com.beastpotato.potato:potato_compiler:2.8'
    compile 'org.glassfish.main:javax.annotation:4.0-b33'
    compile 'com.j256.ormlite:ormlite-core:4.48'
    ...
}
...

• com.beastpotato.potato:potato_api is the library containing annotation deffinitions and other various utility classes used by genereated classes.
• com.beastpotato.potato:potato_compiler is the annotation processor that converts annotated data into generated classes for you to use.
• org.glassfish.main:javax.annotation is needed for the generated classes.
• com.j256.ormlite:ormlite-core:4.48 is needed ONLY if you are using the @JsonToModel with modelType = Constants.ModelType.GSON_AND_ORM_LITE_COMPAT.

We will define an endpoint for getting movie and tv show data in json format from the server.

1. Create class and add annotation.

@Endpoint(httpMethod = Constants.Http.GET, relativeUrl = "/discover/{discover_type}", jsonExample = "paste sample json response here")
public abstract class DiscoverMovieEndpoint {
...
}

2. In the endpoint definition class add fields that will be converted into Url Params, Url Path Params, Header Params and body.

  ...
  @UrlPathParam("discover_type")
  String discoverType;

  @UrlParam("api_key")
  String apiKey;

  @UrlParam("page")
  Integer page;

  @UrlParam("sort_by")
  String sortBy;

  @HeaderParam("Content-Type")
  String contentType;
  
  @Body
  String body;
  ...
  ```
  
3. This step is optional but you can add validation logic. 
  ```java
  ...
  public class Validator {

    @Validation(fieldName = "api_key")
    public static boolean isApiKeyValid(String key){
        return key != null;
    }

    @Validation(fieldName = "page")
    public static boolean isPageNumberValid(Integer page){
        return page >= 1 && page <= 1000;
    }
    
    @Validation(fieldName = "discover_type")
    public static boolean isDiscoveryTypeValid(String discoveryStr){
        return discoveryStr!=null && (discoveryStr.equals("tv") || discoveryStr.equals("movie"));
    }
  }
  ```

## 4. Build! 
This will generate **DiscoverMovieEndpointApiRequest** in app>build>generated>source>apt>debug>packagename> aswell as **DiscoverMovieEndpointApiResponse**  in app>build>generated>source>apt>debug>packagename>response. 
* **DiscoverMovieEndpointApiRequest** contains getters and setters for the fields we defined in step **3.2** aswell as logic for validation and making the network call and parsing the response to POJO model. 
* **DiscoverMovieEndpointApiResponse** contains POJO model representing json string set in **jsonExample** parameter in step **3.1**.

## 5. Use the generated classes.
1. Add internet permission to AndroidManifest.xml

```xml
<uses-permission android:name="android.permission.INTERNET" />

2. Set values in the Request object.

...
DiscoverMovieEndpointApiRequest discoverRequest = new DiscoverMovieEndpointApiRequest("http://api.themoviedb.org/3",getApplicationContext());
discoverRequest.setApiKey("2e2ddf0d141ab64938cf49b95e458392");
discoverRequest.setContentType("application/json");
discoverRequest.setDiscoverType("movie");
discoverRequest.setPage(10);
...

3. This step is optional. You can handle field validation failures.

...
List<DiscoverMovieEndpointApiRequest.Fields> invalidFields = discoverRequest.validateFields();
for(DiscoverMovieEndpointApiRequest.Fields field : invalidFields){
    Toast.makeText(getApplicationContext(),"Field "+field.name()+" failed validation!",Toast.LENGTH_LONG).show();
    switch (field) {
        case apiKey:
            //handle case where apiKey is null
            break;
        case page:
            //handle case where page number is less than 1 or greater than 100
            break;
    }
}
...

4. Send request and handle response.

discoverRequest.send(new ApiRequest.RequestCompletion<DiscoverMovieEndpointApiResponse>() {
    @Override
    public void onResponse(DiscoverMovieEndpointApiResponse data) {
        textView.setText("First movie title in response:" + data.getResults().get(0).getOriginalTitle());
    }

    @Override
    public void onError(VolleyError error) {
        error.printStackTrace();
        Toast.makeText(getApplicationContext(),"request failed!",Toast.LENGTH_LONG).show();
    }
});

• Simple example project available in this repository. Go to the app module or click HERE.
• Advanced example project available HERE. This project demonstrates use of Potato Library with Android Data Binding Library.

#Other Annotations

• fields annotated with this annotation will be turned into POJO representation of jsonString value

  ...
  public class TestJsonStrings {
  @JsonToModel(jsonString = "" +
          "{\"employees\":[\n" +
          "    {\"firstName\":\"John\", \"lastName\":\"Doe\"},\n" +
          "    {\"firstName\":\"Anna\", \"lastName\":\"Smith\"},\n" +
          "    {\"firstName\":\"Peter\", \"lastName\":\"Jones\"}\n" +
          "]}")
  public String EmployeesModel;
  
  @JsonToModel(jsonString = "{\n" +
          "  \"firstName\": \"John\",\n" +
          "  \"lastName\": \"Smith\",\n" +
          "  \"isAlive\": true,\n" +
          "  \"age\": 25,\n" +
          "  \"address\": {\n" +
          "    \"streetAddress\": \"21 2nd Street\",\n" +
          "    \"city\": \"New York\",\n" +
          "    \"state\": \"NY\",\n" +
          "    \"postalCode\": \"10021-3100\"\n" +
          "  },\n" +
          "  \"phoneNumbers\": [\n" +
          "    {\n" +
          "      \"type\": \"home\",\n" +
          "      \"number\": \"212 555-1234\"\n" +
          "    },\n" +
          "    {\n" +
          "      \"type\": \"office\",\n" +
          "      \"number\": \"646 555-4567\"\n" +
          "    },\n" +
          "    {\n" +
          "      \"type\": \"mobile\",\n" +
          "      \"number\": \"123 456-7890\"\n" +
          "    }\n" +
          "  ],\n" +
          "  \"children\": [],\n" +
          "  \"spouse\": null\n" +
          "}")
  public String PersonModel;

  will be tuned into

  • use modelType = Constants.ModelType.GSON_AND_ORM_LITE_COMPAT if you want the generated model to be compatible with OrmLite database. Remember to include compile 'com.j256.ormlite:ormlite-core:4.48' in app module's build.gradle