Foxit PDF SDK For Web - V11.0.4

# Signature Service API

# Overview

The SignatureService class is designed for customizing the PDF signature validation logic. By configuring a custom signature verification callback, developers can forward signature validation requests to backend services or integrate third-party verification mechanisms.

# Main Methods

# setVerifyHandler(handler: VerifySignatureHandler)

  • Functionality: Set the signature verification callback function. When the PDF viewer needs to validate a signature, it will invoke this handler.
  • Parameters:
    • handler: A function of type VerifySignatureHandler, which handles signature verification.
  • Return Value: None
  • Version: Supported since version 11.0.0

# Description of handler

  • handler is an asynchronous function, typically defined as follows

    async (signatureField, plainContent, signedData, hasDataOutOfScope) => { ... }

  • Within the handler, developers can access information related to the signature field (e.g., filter, subfilter, signer) and forward the original content and signature data to backend services for validation.

# Signature Verification Process Description

  • The signature verification process is triggered in the following scenarios:

    1. Triggered by JavaScript Action: For example, when the document is opened (PDFDoc open action) or when the mouse button is released over the annotation area (ANNOT_MOUSE_BUTTON_RELEASED), signature verification is performed automatically.

    2. Triggered by User Action: When the user clicks on a signed signature field, the signature verification process is initiated.

    3. Calling the PDFSignature.verify Method: When using the verify method in PDFSignature, if the verifyHandler option is not specified, the handler set via SignatureService.setVerifyHandler will be used by default.

  • Note：

    • The PDFDoc.verifySignature method does not use the handler set in SignatureService by default; you need to specify it explicitly.

# Example

const service = pdfViewer.getSignatureService();
service.setVerifyHandler(async (signatureField, plainContent, signedData, hasDataOutOfScope) => {
    const filter = await signatureField.getFilter();
    const subfilter = await signatureField.getSubfilter();
    const signer = await signatureField.getSigner();

    const formdata = new FormData();
    formdata.append("filter", filter);
    formdata.append("subfilter", subfilter);
    formdata.append("signer", signer);
    formdata.append("plainContent", new Blob([plainContent]), "plainContent");
    formdata.append("signedData", new Blob([signedData]), "signedData");
    
    const response = await fetch('https://<server>:<port>/<path/to/>verify', {
        method: 'POST',
        body: formdata
    });
    return parseInt(await response.text());
});

# Notes

  • Must Set a Verification Callback: Before initiating the signature verification process, make sure to set the handler using SignatureService.setVerifyHandler; otherwise, the verification process will throw an exception.

  • Handler Return Value: The handler should return a numeric value representing the verification result (refer to the Form Signature Fields documentation for related information).

  • Asynchronous Support: The handler supports asynchronous operations, making it convenient for integration with backend services.

  • Scope of Applicability: The handler set in SignatureService is only effective for JavaScript Action verification processes and when PDFSignature.verify does not specify a handler. It does not apply to PDFDoc.verifySignature. :

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