How to add Digital Signature in Java Applications?

Digital signatures have become a cornerstone of secure, paperless workflows—especially in enterprise-grade Java applications. Whether you’re building financial systems, HR tools, or legal platforms, integrating digital signatures ensures document authenticity, integrity, and compliance with standards like DSC.

In this blog, we’ll walk you through how to add digital signature in Java, covering both the conceptual understanding and practical implementation. From signing PDFs to integrating with a signature API like KAiZEN, this guide is tailored for developers looking to streamline and secure their document processes with Java.

How to integrate eSignature into Java Applications:

Step 1: Define Your Signers and Signing Order

Let’s define the below two users which the order of signing.

Signer Information

Signer Name	Order	Signer Email
Signer 1	1	signer1@gmail.com
Signer 2	2	signer2@gmail.com

Step 2: Make an HTTP Call to KAiZEN’s API

Need to make a secure HTTP Callout to call the KAiZEN “Initiate Sign API” request as per the below details:

HTTP Request Parameters

Parameters Name	Value
Content-Type	application/json
Method	POST
Endpoint	https://fa-kaizen-prod.azurewebsites.net/api/Sign/RequestStr?code=RTa1A0GW5Yl92OF54-73lRqglLFCt_0pVcg86hWf1EjtAzFuNROcdA==
Body	JSON Body with parameters

Important Request Body Parameters

Parameters Name	Description	Required
docContent	Base64 Content for the PDF File	Yes
docName	Name of the File	Yes
appToken	Unique Code to initiate the request	Yes
requesterEmail	Email address of the person initiating the request	Yes
requesterName	Name of the person initiating the request	Yes
description	Describes the document	No
signers	An array of the signers who needs to sign the document in the pre-defined order.	Yes
CallBackURL	CallbackURL defines the url on which the KAiZEN should send a response once all the signers signs the document. It can be webservice url of Salesforce or any external page. Eg: https://duumy.my.salesforce- sites.com/services/apexrest/KaizenCallbackURL/	No
newRequestEmailSubject	Describes the email subject	No
requesterMessage	Describes the prompt eSignature field	No
docDescription	Describes the document	No

Step 3: Java Code Sample for Integration

Let’s define the below two users which the order of signing.

OkHttpClient client = new OkHttpClient().newBuilder()
.build();
MediaType mediaType = MediaType.parse("application/json");
RequestBody body = RequestBody.create(mediaType, "{\n \"docContent\":\"<>\",\n \"requesterEmail\": \"xyz@gmail.com\",\n \"requesterName\": \"XYZ\",\n \"requesterPhone\": \"xxxxx-xxx-xxxx\",\n \"description\" :\"\",\n \"newRequestEmailSubject\":\"You have a document to sign\",\n \"requesterMessage\": \"Kindly eSign your KAiZEN Test PDF\",\n \"signers\": [\n {\n \"signerEmail\": \"signer1@gmail.com\",\n \"signerName\": \"Signer1\",\n \"signerPhone\": \"xx-xxx-xxxx-xxx\",\n \"order\": \"1\",\n \"signerRole\": \"signer\"\n \n },{\n \"signerEmail\": \"signer2@gmail.com\",\n \"signerName\": \"Signer2\",\n \"signerPhone\": \"xxx-xxx-xxxx-xxxx\",\n \"order\": \"2\",\n \"signerRole\": \"reviewer\"\n \n }\n ],\n \n \"docDescription\": \"Base 64 string based test doc\",\n \"callbackurl\": \"\"\n}");
Request request = new Request.Builder()
.url("https://fa-kaizen-staging.azurewebsites.net/api/Sign/RequestStr?code=mLgEBTpi9dfooQ6TB9gc7sa4qiIuuxmqQYoTx8nQQ1StAzFu93g06A==")
.method("POST", body)
.addHeader("Content-Type", "application/json")
.build();
Response response = client.newCall(request).execute();

Sample HTTP Response:

{
“FailRules”: [],
“Data”: {
“SignRequestId”: “01HV6MEARQD3X8ZXXX5FR3YDB8”,
“RequestNo”: “KAiZEN-118”
}
}

Once the request is submitted, it will send a response with the request Id. If the callback url is configured, it will send a signed copy of the document on the defined url, once all the signers will sign and review the document.

Once the request is sent out to the signers, each signer will receive an email to sign the document in the order as defined in the request.

How KAiZEN eSign Works

Check Your Inbox

The signer will receive an email from KAiZEN with a prompt to sign the document.
Click to Start Signing

Inside the email, click the “Sign here” button. This opens the document in the secure KAiZEN signing editor.
Sign the Document

After clicking on the “Sign Here” button. You’ll get a popup where you can choose the following methods to eSign:
- Initials
- Draw your signature
- Upload an image of your signature
- Recently Used Signs
Submit and Done

Once you’ve placed your signature, click Submit. The next signer in the sequence will then be notified.
After All Signers Complete

Once every signer has completed the process:
- Each signer will receive an email with the final signed document.
- If a callback URL was configured, a copy of the signed document will be automatically sent to that system (e.g., Java or your application).

Conclusion

Integrating digital signatures into your Java application boosts security, ensures compliance, and streamlines document workflows. With tools like KAiZEN, it’s easier than ever to implement reliable and scalable eSigning features directly into your Java stack.

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How to integrate eSignature into Java Applications: