PDF.co Web API – PDF To JSON API – Java – Convert PDF To JSON From URL

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Let’s review the Source code and its output first, then we’ll analyze it.

Source Code:

ByteScoutWebApiExample.iml

      
<?xml version="1.0" encoding="UTF-8"?>
<module type="JAVA_MODULE" version="4">
  <component name="NewModuleRootManager" inherit-compiler-output="true">
    <exclude-output />
    <content url="file://$MODULE_DIR{code}quot;>
      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
    </content>
    <orderEntry type="inheritedJdk" />
    <orderEntry type="sourceFolder" forTests="false" />
    <orderEntry type="library" name="com.google.code.gson:gson:2.8.1" level="project" />
    <orderEntry type="library" name="com.squareup.okhttp3:okhttp:3.8.1" level="project" />
  </component>
</module>
    

main.java

package com.company;

import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import okhttp3.*;

import java.io.*;
import java.net.*;
import java.nio.file.Path;
import java.nio.file.Paths;

public class Main
{
    // The authentication key (API Key).
    // Get your own by registering at https://app.pdf.co/documentation/api
    final static String API_KEY = "***********************************";

    // Source PDF file
    final static Path SourceFile = Paths.get(".\\sample.pdf");
    // Comma-separated list of page indices (or ranges) to process. Leave empty for all pages. Example: '0,2-5,7-'.
    final static String Pages = "";
    // PDF document password. Leave empty for unprotected documents.
    final static String Password = "";
    // Destination JSON file name
    final static Path DestinationFile = Paths.get(".\\result.json");


    public static void main(String[] args) throws IOException
    {
        // Create HTTP client instance
        OkHttpClient webClient = new OkHttpClient();

        // 1. RETRIEVE THE PRESIGNED URL TO UPLOAD THE FILE.
        // * If you already have a direct file URL, skip to step 3.

        // Prepare URL for `Get Presigned URL` API call
        String query = String.format(
                "https://api.pdf.co/v1/file/upload/get-presigned-url?contenttype=application/octet-stream&name=%s",
                SourceFile.getFileName());

        // Prepare request
        Request request = new Request.Builder()
                .url(query)
                .addHeader("x-api-key", API_KEY) // (!) Set API Key
                .build();
        // Execute request
        Response response = webClient.newCall(request).execute();

        if (response.code() == 200)
        {
            // Parse JSON response
            JsonObject json = new JsonParser().parse(response.body().string()).getAsJsonObject();

            boolean error = json.get("error").getAsBoolean();
            if (!error)
            {
                // Get URL to use for the file upload
                String uploadUrl = json.get("presignedUrl").getAsString();
                // Get URL of uploaded file to use with later API calls
                String uploadedFileUrl = json.get("url").getAsString();

                // 2. UPLOAD THE FILE TO CLOUD.

                if (uploadFile(webClient, API_KEY, uploadUrl, SourceFile))
                {
                    // 3. CONVERT UPLOADED PDF FILE TO JSON

                    PdfToJson(webClient, API_KEY, DestinationFile, Password, Pages, uploadedFileUrl);
                }
            }
            else
            {
                // Display service reported error
                System.out.println(json.get("message").getAsString());
            }
        }
        else
        {
            // Display request error
            System.out.println(response.code() + " " + response.message());
        }
    }

    public static void PdfToJson(OkHttpClient webClient, String apiKey, Path destination file,
        String password, String pages, String uploadedFileUrl) throws IOException
    {
        // Prepare URL for `PDF To JSON` API call
        String query = "https://api.pdf.co/v1/pdf/convert/to/json";

        // Make correctly escaped (encoded) URL
        URL url = null;
        try
        {
            url = new URI(null, query, null).toURL();
        }
        catch (URISyntaxException e)
        {
            e.printStackTrace();
        }

        // Create JSON payload
		String jsonPayload = String.format("{\"name\": \"%s\", \"password\": \"%s\", \"pages\": \"%s\", \"url\": \"%s\"}",
                destinationFile.getFileName(),
                password,
                pages,
                uploadedFileUrl);

        // Prepare request body
        RequestBody body = RequestBody.create(MediaType.parse("application/json"), jsonPayload);
        
        // Prepare request
        Request request = new Request.Builder()
            .url(url)
            .addHeader("x-api-key", API_KEY) // (!) Set API Key
            .addHeader("Content-Type", "application/json")
            .post(body)
            .build();
        
        // Execute request
        Response response = webClient.newCall(request).execute();
        

        if (response.code() == 200)
        {
            // Parse JSON response
            JsonObject json = new JsonParser().parse(response.body().string()).getAsJsonObject();

            boolean error = json.get("error").getAsBoolean();
            if (!error)
            {
                // Get URL of generated JSON file
                String resultFileUrl = json.get("url").getAsString();

                // Download JSON file
                downloadFile(webClient, resultFileUrl, destinationFile.toFile());

                System.out.printf("Generated JSON file saved as \"%s\" file.", destinationFile.toString());
            }
            else
            {
                // Display service reported error
                System.out.println(json.get("message").getAsString());
            }
        }
        else
        {
            // Display request error
            System.out.println(response.code() + " " + response.message());
        }
    }

    public static boolean uploadFile(OkHttpClient webClient, String apiKey, String url, Path sourceFile) throws IOException
    {
        // Prepare request body
        RequestBody body = RequestBody.create(MediaType.parse("application/octet-stream"), sourceFile.toFile());

        // Prepare request
        Request request = new Request.Builder()
                .url(url)
                .addHeader("x-api-key", apiKey) // (!) Set API Key
                .addHeader("content-type", "application/octet-stream")
                .put(body)
                .build();

        // Execute request
        Response response = webClient.newCall(request).execute();

        return (response.code() == 200);
    }

    public static void downloadFile(OkHttpClient webClient, String url, File destinationFile) throws IOException
    {
        // Prepare request
        Request request = new Request.Builder()
                .url(url)
                .build();
        // Execute request
        Response response = webClient.newCall(request).execute();

        byte[] fileBytes = response.body().bytes();

        // Save downloaded bytes to file
        OutputStream output = new FileOutputStream(destinationFile);
        output.write(fileBytes);
        output.flush();
        output.close();

        response.close();
    }
}

Output:

Though this code snippet is self-explanatory, let’s review the main parts of it. If we want we can divide code into two parts. First, we’re uploading the input PDF and getting the pubic URL; and Secondly, we’re using that URL to convert to JSON and save to the output file. At the beginning of code, we’re gathering all necessary information such as PDF.co API key, Source File Path, Pages to be converted, Destination JSON File Path, etc.

In order to upload a PDF file to PDF.co cloud, we need a pre-signed URL. As name suggest, the PDF.co API endpoint /v1/file/upload/get-presigned-url is used to get the pre-signed URL. This API endpoint expects the input file name as an input argument, and it returns the pre-signed URL (json.get(“presignedUrl”)) along with the public URL (json.get(“url”)). Then we’re uploading an input PDF file with a PUT request to this pre-signed URL. Upon a successful file upload, the public URL points to the uploaded source file. This public URL is temporary and only available for a few time due to security reasons.

PDF.co API endpoint /v1/pdf/convert/to/json is used to convert PDF to JSON format. The JSON payload for all input parameters is prepared and passed in the request body. The response contains a URL that points to converted JSON data. This API endpoint has in-built support to work with scanned PDF files. We can customize the JSON creation by providing additional parameters. The following are examples of additional input parameters.

Please refer to PDF.co documentation for more information regarding various parameters available.

Execute and play with this code in your machine to get a better idea. Thank you for reading!

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