The properties file is one of the data formats for storing configuration and settings data in software projects.

This is mainly used in Java and Windows applications to configure the settings that are going to change as per times environment or user profiles.

properties file contains rows with line breaks. Each row of the line contains key and values.

environment=production

Here key is the variable name that has a value production, and the key and values are separated by an equal(=) or colon(:) symbol sign.

The properties files are suitable for simple settings data and not suitable for complex structures of configuration. You can use yaml or toml file for nested settings configuration data.

These are similar to simple hashtables where each key and value are simple values.

valid properties file examples are

key=value
key1= value 1
key2:value2

Properties file extension Advantages

  • It is easy to read and write and the format is human-readable
  • Supports simple configuration with keys and values
  • Mainly used in Java programming language and related frameworks but supports all popular programming language
  • Can write comments
  • properties contents are similar to Ini format in windows
  • Can maintain a separate file for language strings during Internalization
  • Maintain a single place for storing reusable configuration in Java applications
  • Lines Start with: and = are and blank lines ignored by the processor

Disadvantages

  • No support for binary data
  • Complex values like the table are not supported
  • Not suitable for complex nested configuration
  • Objects and tables data are not supported

properties file use cases

  • Properties files are used to maintain environment configuration data for development, testing, staging, and production
  • Configuration and settings of the software applications
  • Maintain separate properties for each local or language in I18N applications

Properties file extension

The extension tells the type of file.

use any IDE or Text Editor with file extension .properties file

Rules

  • By default, the properties files extension is .properties
  • It supports UTF-8 encoding format only
  • Supports whitespaces, tabs, and newlines asci code

Properties file MIME format type - text/plain

MIME stands for Multipurpose Internet Mail Extensions, and it is a request and response format that sent between client and server

Content-Type and accept headers in a request object are specified with this format. Below is the mime type for these documents

text/x-java-properties

and request contains the below value for INI data sending over the internet

Content-type : text/x-java-properties

Default encoding

Default encoding for properties file ISO 8859-1character encoding.

All the reading and writing object using Java has supported this default encoding

How do you create and edit property files?

Plain editor or popular IDE used to create Properties files.

All popular IDE supports the INI file extension and provides plugins to validate the INI file content.

  • Notepad++
  • Eclipse
  • Visual Studio Code
  • Intelli IDEA