Why Does My Java Program Fail to Download HTTPS Files with 'unable to find valid certification path to requested target'?

Unable to Find Valid Certification Path to Requested Target

When downloading a file from an HTTPS server via Java, you might encounter the following error:

Understanding the Error

This error indicates a problem with client-server authentication. HTTPS servers use certificates to establish a secure connection. The client (Java program) must trust the server's certificate to proceed with the download.

Possible Cause: Server Has a Self-Signed Certificate

Self-signed certificates are not issued by a trusted authority. Java's default trust store does not contain these certificates, causing the authentication failure.

Solution

To ignore client-server authentication, you can add the server's certificate to the Java trust store. Here's how:

1. Obtain the Certificate:

• Navigate to the website using a browser.
• Click on the lock icon in the address bar.
• Select "Certificate" and export the certificate as a CER or CRT file.

2. Add the Certificate to the Trust Store:

There are two ways to do this:

a. Using keytool:

• Open a command prompt.
• Navigate to JAVA_HOME/jre/lib/security.
• Run the following command:

b. Using -D parameter:

• Run your Java application with the following parameter:

3. Replace certificate.cer and mytruststore.jks with the actual file names.

After adding the certificate to the trust store, your Java program should be able to download the file from the HTTPS server without the authentication error.

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