Step by Step Guide to Building a pdfFiller API Integration in Java

Introduction

Hey there, fellow code wranglers! Ready to supercharge your Java app with some serious document handling capabilities? Look no further than the pdfFiller API. This nifty tool lets you upload, create, fill, and download PDF forms with ease. In this guide, we'll walk through integrating this powerhouse into your Java project. Buckle up!

Prerequisites

Before we dive in, make sure you've got:

• A Java development environment (I know you've got this covered!)
• pdfFiller API credentials (grab 'em from the pdfFiller developer portal)
• Your favorite Java HTTP client and JSON parser (we'll use OkHttp and Gson in our examples)

Setting up the project

First things first, let's get our project set up:

1. Create a new Java project in your IDE of choice.
2. Add the following dependencies to your pom.xml (if you're using Maven):

<dependencies>
    <dependency>
        <groupId>com.squareup.okhttp3</groupId>
        <artifactId>okhttp</artifactId>
        <version>4.10.0</version>
    </dependency>
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.9</version>
    </dependency>
</dependencies>

Authentication

pdfFiller uses OAuth 2.0 for authentication. Here's a quick implementation:

public class PdfFillerAuth {
    private static final String TOKEN_URL = "https://api.pdffiller.com/v1/oauth/access_token";
    private static final String CLIENT_ID = "your_client_id";
    private static final String CLIENT_SECRET = "your_client_secret";

    public static String getAccessToken() throws IOException {
        OkHttpClient client = new OkHttpClient();
        RequestBody formBody = new FormBody.Builder()
                .add("grant_type", "client_credentials")
                .add("client_id", CLIENT_ID)
                .add("client_secret", CLIENT_SECRET)
                .build();

        Request request = new Request.Builder()
                .url(TOKEN_URL)
                .post(formBody)
                .build();

        try (Response response = client.newCall(request).execute()) {
            if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
            
            String responseBody = response.body().string();
            JsonObject jsonObject = JsonParser.parseString(responseBody).getAsJsonObject();
            return jsonObject.get("access_token").getAsString();
        }
    }
}

Pro tip: Store your access token securely and refresh it when needed!

Core API Integration Steps

Uploading a document

Let's get that PDF up to pdfFiller:

public static String uploadDocument(String filePath, String accessToken) throws IOException {
    OkHttpClient client = new OkHttpClient();
    RequestBody requestBody = new MultipartBody.Builder()
            .setType(MultipartBody.FORM)
            .addFormDataPart("file", "document.pdf",
                    RequestBody.create(MediaType.parse("application/pdf"), new File(filePath)))
            .build();

    Request request = new Request.Builder()
            .url("https://api.pdffiller.com/v1/document")
            .post(requestBody)
            .addHeader("Authorization", "Bearer " + accessToken)
            .build();

    try (Response response = client.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        
        String responseBody = response.body().string();
        JsonObject jsonObject = JsonParser.parseString(responseBody).getAsJsonObject();
        return jsonObject.get("id").getAsString();
    }
}

Creating a fillable form

Now, let's make that PDF fillable:

public static void createFillableForm(String documentId, String accessToken) throws IOException {
    OkHttpClient client = new OkHttpClient();
    RequestBody requestBody = RequestBody.create(MediaType.parse("application/json"), "{}");

    Request request = new Request.Builder()
            .url("https://api.pdffiller.com/v1/fillable_template/" + documentId)
            .post(requestBody)
            .addHeader("Authorization", "Bearer " + accessToken)
            .build();

    try (Response response = client.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        // Form created successfully
    }
}

Filling out the form

Time to populate those fields:

public static void fillForm(String documentId, Map<String, String> fieldValues, String accessToken) throws IOException {
    OkHttpClient client = new OkHttpClient();
    Gson gson = new Gson();
    String jsonBody = gson.toJson(fieldValues);

    RequestBody requestBody = RequestBody.create(MediaType.parse("application/json"), jsonBody);

    Request request = new Request.Builder()
            .url("https://api.pdffiller.com/v1/document/" + documentId + "/fill")
            .post(requestBody)
            .addHeader("Authorization", "Bearer " + accessToken)
            .build();

    try (Response response = client.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        // Form filled successfully
    }
}

Downloading the completed document

Finally, let's grab that filled PDF:

public static void downloadDocument(String documentId, String outputPath, String accessToken) throws IOException {
    OkHttpClient client = new OkHttpClient();

    Request request = new Request.Builder()
            .url("https://api.pdffiller.com/v1/document/" + documentId + "/download")
            .get()
            .addHeader("Authorization", "Bearer " + accessToken)
            .build();

    try (Response response = client.newCall(request).execute()) {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        
        try (InputStream inputStream = response.body().byteStream();
             OutputStream outputStream = new FileOutputStream(outputPath)) {
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
        }
    }
}

Error Handling and Best Practices

• Always check for HTTP status codes and handle errors gracefully.
• Implement exponential backoff for rate limiting.
• Use environment variables or a secure vault for storing API credentials.

Testing the Integration

Don't forget to test! Write unit tests for each method and integration tests for the full workflow. Your future self will thank you.

Optimization and Performance

• Cache access tokens to reduce API calls.
• Use asynchronous operations for non-blocking I/O.

Conclusion

And there you have it! You've just built a robust pdfFiller API integration in Java. With this power, you can automate document workflows, create dynamic forms, and much more. The possibilities are endless!

Resources

• pdfFiller API Documentation
• Sample Code Repository

Now go forth and conquer those PDFs! Happy coding!