Common Module

The common module provides shared utilities, constants, and enumerations that are used across both the client and server components of the Light-4j framework.

Components

ContentType

ContentType is an enumeration that defines standard HTTP Content-Type header values. It simplifies code maintenance by replacing hardcoded strings with strongly typed constants.

Supported Types:

• application/json
• text/xml
• application/xml
• application/yaml
• application/x-www-form-urlencoded
• multipart/form-data
• … and more.

It also includes a helper method toContentType(String value) to convert a string header value into the corresponding enum constant.

SecretConstants

This class defines standard keys for sensitive values found in secret.yml or other configuration files. These constants ensure consistency when accessing secrets across different modules.

Common Constants:

• Certificates: serverKeystorePass, serverTruststorePass, clientKeystorePass, etc.
• OAuth2: authorizationCodeClientSecret, clientCredentialsClientSecret, etc.
• Infrastructure: consulToken, emailPassword.

DecryptUtil

DecryptUtil is a critical utility for handling encrypted sensitive values within configuration files (like secret.yml). It enables the “Encrypt-Once, Deploy-Everywhere” pattern where secrets are stored in version control in an encrypted format and decrypted only at runtime.

How it works

1. Iterative Decryption: The decryptMap method recursively iterates through a configuration map (nested maps and lists).
2. Detection: It identifies values that start with the CRYPT prefix.
3. Decryption: When an encrypted value is found, it uses the configured Decryptor implementation to decrypt it.

Usage

The framework typically handles this automatically when loading secret.yml. However, if you are loading custom configuration files with encrypted values, you can use it directly:

Map<String, Object> myConfig = Config.getInstance().getJsonMapConfig("my-config");
if(myConfig != null) {
    // recursively decrypt all values in the map
    DecryptUtil.decryptMap(myConfig);
}

Decryptor Configuration

DecryptUtil relies on a Decryptor implementation being registered in service.yml. The default implementation typically uses AES encryption.

For example, in service.yml:

singletons:
  - com.networknt.decrypt.Decryptor:
      - com.networknt.decrypt.AESDecryptor

For more details on generating keys and encrypting values, refer to the Decryptor Module.