# PropertyFile

## Introduction

Apache Ant provides an optional task for editing property files. This is very useful when wanting to make unattended modifications to configuration files for application servers and applications. Currently, the task maintains a working property file with the ability to add properties or make changes to existing ones. Since Ant 1.8.0 comments and layout of the original properties file are preserved.

Since Ant 1.8.2 the linefeed-style of the original file will be preserved as well, as long as style used to be consistent. In general, linefeeds of the updated file will be the same as the first linefeed found when reading it.

## PropertyFile Task

### Parameters

Attribute | Description | Required
--- | --- | ---
file | Location of the property file to be edited | Yes
comment | Header for the file itself | No
jdkproperties | Use `java.lang.Properties`, which will lose comments and layout of file. since Ant 1.8.0 | No; default is false

The boolean attribute jdkproperties is provided to recover the previous behaviour of the task, in which the layout and any comments in the properties file were lost by the task.

### Parameters specified as nested elements

#### Entry

Use nested `<entry>` elements to specify actual modifications to the property file itself.

Attribute | Description | Required
--- | --- | ---
key | Name of the property name/value pair | Yes
value | Value to set (=), to add (+) or subtract (-) | At least one must be specified, if operation is not del
default | Initial value to set for a property if it is not already defined in the property file. For type date, an additional keyword is allowed: now
type | Regard the value as: int, date or string (default) | No; defaults to string
operation | One of the following operations: for all datatypes: del : deletes an entry + : adds a value to the existing value = : sets a value instead of the existing value (default) for date and int only: - : subtracts a value from the existing value | No; defaults to =
pattern | For int and date type only. If present, values will be parsed and formatted accordingly. | No
unit | The unit of the value to be applied to date +/- operations. Valid Values are: millisecond second minute hour day (default) week month year This only applies to date types using a +/- operation. | No; defaults to day

The rules used when setting a property value are shown below. The operation occurs after these rules are considered.

- If only value is specified, the property is set to it regardless of its previous value.
- If only default is specified and the property previously existed in the property file, it is unchanged.
- If only default is specified and the property did not exist in the property file, the property is set to default.
- If value and default are both specified and the property previously existed in the property file, the property is set to value.
- If value and default are both specified and the property did not exist in the property file, the property is set to default.

### Examples

The following changes the `my.properties` file. Assume `my.properties` looks like:

    # A string value
    akey=original value

    # The following is a counter, which will be incremented by 1 for
    # each time the build is run.
    anint=1

After running, the file would now look like

    #My properties
    #Wed Aug 31 13:47:19 BST 2005
    # A string value
    akey=avalue

    # The following is a counter, which will be incremented by 1 for
    # each time the build is run.
    anint=2

    adate=2005/08/31 13\:47

    formated.int=0014

    formated.date=243 13\:47

The slashes conform to the expectations of the Properties class. The file will be stored in a manner so that each character is examined and escaped if necessary.

The layout and comment of the original file is preserved. New properties are added at the end of the file. Existing properties are overwritten in place.

    <propertyfile file="my.properties"
                  comment="My properties">
        <entry key="akey" value="avalue"/>
        <entry key="adate" type="date" value="now"/>
        <entry key="anint" type="int" default="0" operation="+"/>
        <entry key="formated.int" type="int" default="0013" operation="+" pattern="0000"/>
        <entry key="formated.date" type="date" value="now" pattern="DDD HH:mm"/>
    </propertyfile>

To produce dates relative from today:

    <propertyfile file="my.properties"
                  comment="My properties">
        <entry key="formated.date-1"
               type="date" default="now" pattern="DDD"
               operation="-" value="1"/>
        <entry key="formated.tomorrow"
               type="date" default="now" pattern="DDD"
               operation="+" value="1"/>
    </propertyfile>

Concatenation of strings:

    <propertyfile file="my.properties"
                  comment="My properties">
        <entrykey="progress" default="" operation="+" value="."/>
    </propertyfile>

Each time called, a . will be appended to `progress`

Pumps the project version to the next minor version (increase minor and set `patch=0`):

    <target name="nextMinorVersion">
        <property name="header"
                  value="##Generated file - do not modify!"/>
        <propertyfile file="version.properties" comment="${header}">
            <entry key="product.build.major" type="int"  value="3"/>
            <entry key="product.build.minor" type="int"  operation="+"/>
            <entry key="product.build.patch" type="int"  value="0"/>
            <entry key="product.build.date"  type="date" value="now"/>
        </propertyfile>
    </target>

After running this target the version changed e.g. from 3.2.2 to 3.3.0.