PropertiesDateien

PropertiesDateien, often written as properties files, are plain-text files used to store simple key-value pairs for configuration and localization. They are widely associated with Java applications, but the format is used by various tools and frameworks to externalize strings and settings. A typical properties file contains one key per line with its corresponding value, for example: greeting=Hello, app.title=Properties example, database.url=jdbc:mysql://localhost/db. Lines may include comments beginning with # or !, and a separator can be = or : or whitespace. Long values may be continued on the next line using a trailing backslash.

Syntax and conventions: Each non-empty, non-comment line defines a mapping from a key to a value. The first unescaped =, :, or whitespace separates the key from the value. Whitespace around separators is ignored. Keys are case-sensitive. Special characters can be escaped using backslashes, and non-ASCII characters are traditionally written with Unicode escapes like \u00e4; many tools also support UTF-8, depending on how the file is read.

Encoding and handling: Java’s properties APIs historically read ISO-8859-1 by default and represent non-ASCII characters with escapes. Some environments allow reading and writing with UTF-8 via alternative methods or XML-based property formats. For localization, files are typically named with locale suffixes, such as messages_en.properties or messages_de.properties, and loaded via resource bundles.

Usage and limitations: Properties files are simple, human-readable, and easy to parse, making them well suited for small configurations and i18n strings. They are not ideal for structured data, large configurations, or complex hierarchies. For more complex needs, formats like YAML, JSON, or XML may be preferable.

See also: Property files, ResourceBundle, internationalization.