The Format of Properties Files

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The Format of Properties Files

In this section, we will discuss the format of a properties file, such as

A properties file is a simple text file. The file contains a list of key=value pairs, such as

# This is the default file

The default encoding of a properties file is assumed to be UTF-8. If you want to use a different encoding, please refer to the Use Encoding Other Than UTF-8 section.

A properties file is usually used to contain the internationalization labels of an application, but technically you could use it in any situation you'd like[1].

  1. If it is used for internationalization labels, it will be loaded automatically. If you want to use it in other situations, you have to invoke Maps.load(Map, InputStream, boolean) or similar to load it manually.

Specify a Value with Multiple Lines

By default, a property is a text specified right after the equal sign. If the property's value has multiple lines, you could use the following format:

line 1
line 2

Notice that the curly braces must be followed by a line break immediately, and the right brace (}) must be the only character in the line.

Then you should put the value in a multiple-line label:

<label multiline="true" value="${labels.multilines}"/>

Render Multiple Lines

Alternatively, you can write a value with <br>:

lines=1st line <br> 2nd line

Then render it in an HTML span

<zk xmlns:h="native">

Specify Segmented Keys

Since all internationalization labels are stored in the same scope, it is common to separate them by naming the key with dots (.) like the Java package name. For the sake of description, we call them segmented keys. For example, = Orange
order.fruit.description = A common fruit

It can be simplified by use of the following syntax:

order.fruit.  {
name = Orange
description = A common fruit

As shown, the segmented key could be specified by specifying the prefix and a following right brace ({).

The segmented key could be accessed in two ways.

First, with an implicit object called labels:

<textbox value="${}"/>

Second, with an EL function called l and/or l2:

<?taglib uri="" prefix="c"?>
<label value="${c:l('')}">

Under the hood

The labels object is actually the map returned by Labels.getSegmentedLabels(). Furthermore, if the key of a property contains dots (.), i.e., segmented, all properties with the same prefix are grouped as another map. For example, ${labels.order} (i.e., Labels.getSegmentedLables().get("order")) will return a map containing an entry (fruit) in the above example.

Specify a Comment

You could put a comment line by starting with the sharp sign (#), such as

#This is a comment line that will be ignored when loaded

Use EL Expressions

EL expressions are allowed for a property's value. For example, you could reference a property's value in another property, such as

first=the first label
second=come after ${first}

Since 5.0.7Segmented keys are also allowed:

group1.first=the first group
group2.second=come after ${group1.first}

In addition to referencing another property, you could reference any implicit object specified in ZUML Reference: Implicit Objects if it is part of an HTTP request (excluding component/page).

For example, param references to a request's parameter:

message=Thank ${param.user} for using

Use Encoding Other Than UTF-8

By default, the encoding of properties files is assumed to be UTF-8. If you prefer another encoding, please specify it in a library property called org.zkoss.util.label.web.charset. It also means all properties files must be encoded in the same character set.

For more information, please refer to ZK Configuration Reference.

Version History

Version Date Content
5.0.7 Mar 2011 labels implicit object was introduced to access properties without declaring taglib. Also allows label keys of a.b.c format.

Last Update : 2024/02/01

Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.