properties

The properties driver reads values from .properties files — the format of Java and Spring, application.properties.

import "github.com/insei/tinyconf/drivers/properties"

propertiesDriver, err := properties.New("application.properties")

The driver has its own parser and adds no dependencies.

Keys

The properties tag is a part of the key. Tags of nested structs are the parts before the dots:

type Config struct {
    Name string `properties:"name"`
    HTTP struct {
        Host string `properties:"host"`
        Port int    `properties:"port"`
    } `properties:"http"`
}

name=app
http.host=example.com
http.port=9090

Set the tags of the parents

The key of the nested field is built from the properties tags of its parents. If the HTTP field has no properties tag, the Host field is read from the host key, and the manager logs a warning. Embedded structs without the tag are the exception.

Syntax

The syntax of java.util.Properties:

Element	Example
key and value	port=9090, port: 9090, port 9090
comment	# comment, ! comment
escapes	\t, \n, \r, \f, \\, \uXXXX; \ before any other character is the character
separators and spaces in keys	key\ with\=separators=value
long value on several lines	a backslash at the end of the line, the leading spaces of the next line are skipped

The spaces before the value are skipped, the spaces at the end are a part of the value, like in Java.

Values are strings, they are parsed by the rules of string values like environment variables: true, 9090, 1m30s; lists are comma separated hosts=a,b, maps are labels=env:prod,team:core or the keys labels.env=prod, structs in lists are JSON with the keys by the properties tags: servers=[{"host": "a", "port": 1}].

A key can not be a value and an object at the same time: http=1 and http.port=2 in one file is an error of Parse with the number of the line.

Options

The options are the same as of the yaml driver:

Option	Description
WithFiles(files...)	additional files from the OS file system: application-prod.properties
WithFS(fsys, files...)	files from any fs.FS, embed.FS for example
WithData(name, data)	in-memory content, the name is used in error messages
WithSource(source)	content from a remote storage: consul.Document, etcd.Document
WithOptional()	files can be absent
WithEnvExpansion()	replaces ${VAR} in the content with environment variables
WithWatchInterval(interval)	interval of polling the files for reloading, 5 seconds by default; changes are detected by the events of the file system without waiting for it

Files are merged in the order of addition, like the profiles of Spring:

propertiesDriver, err := properties.New("application.properties",
    properties.WithFiles("application-"+profile+".properties"),
    properties.WithOptional(),
)

Documentation

GenDoc("properties") generates the file with the current values, sorted by the keys. Values of hidden:"true" fields are empty, the special characters are escaped, so the file is read back to the same config.

http.host=example.com
http.port=9090
name=app