The Conditions Element

This element allows you to define conditions which can be used to dynamically change the installer, e.g. the panels shown, the variables set, files parsed, files executed and much more. When you define a condition it will get a type and an id. The id has to be unique. Conditions can be referenced based on this id (e.g. with the RefCondition).

When you define a set of conditions, you just have to write as many <condition> tags as you like.

Condition Types

Dynamic Conditions

There is a number of built-in condition types in IzPack which can be used in an installation description, which are evaluated dynamically at a given moment as soon as they are referenced, depending on the installer state, the processed user inputs and the parameters given to them:

• CompareNumerics Condition
  Set when a certain comparison operation matches two numeric values.
• CompareVersions Condition
  Set when a certain comparison operation matches two version string values.
• Empty Condition
  True if a given value, file or directory is empty.
• Exists Condition
  True if a given variable, file or directory exists.
• Java Condition
  Set based on a static java field or method
• Packselection Condition
  Set when a certain pack is selected for installation.
• Ref Condition
  Set when a another, referenced condition is set.
• Variable Condition
  Set when a certain value matches the value of an IzPack variable.
• User Condition
  Set when a certain user is using the installer.

Aggregate Conditions

There are several aggregate conditions, which logically combine or alter one ore more conditions:

• And Condition
  All nested conditions have to be true.
• Or Condition
  At least one nested condition has to be true.
• Xor Condition
  Exactly one nested condition has to be true
• Not Condition
  The nested condition has to be false (negated state).

Pre-defined Conditions

There is a number of built-in conditions which are statically pre-set on launching the installation and which can be only referenced by their ID:

• izpack.windowsinstall
  True if the current OS is (any) Windows.
• izpack.windowsinstall.xp
  True if the current OS is Windows XP.
• izpack.windowsinstall.2003
  True if the current OS is Windows Server 2003.
• izpack.windowsinstall.vista
  True if the current OS is Windows Vista.
• izpack.windowsinstall.7
  True if the current OS is Windows 7.
• izpack.windowsinstall.8
  True if the current OS is Windows 8.
• izpack.macinstall
  True if the current OS is Mac OS X.
• izpack.linuxinstall
  True if the current OS is (any) Linux.
• izpack.solarisinstall
  True if the current OS is (any) Solaris.
• izpack.solarisinstall.x86
  True if the current OS is (any) Solaris x86.
• izpack.solarisinstall.sparc
  True if the current OS is (any) Solaris Sparc.

Using Conditions

Defining Conditions

<conditions> Element

Conditions are defined in the installation definition as nested <condition> elements of the <conditions/> element.

Foe example: 

• Dynamic Installer Requirements
• ConditionDataValidator
• Panels

<condition> - Attributes

The following attributes must be set in a <condition> element definition:

<condition> - Nested Elements

The condition element can have several child elements depending on the condition type. For instance, the VariableCondition has a name and value child element to specify, which variable should have a certain value to fullfil this condition.

Here is an example which defines four conditions, two VariableConditions, a JavaCondition and a AndCondition which will refer to two of the first conditions:

<conditions>
    <condition type="variable" id="standardinstallation">
        <name>setup.type</name>
        <value>standard</value>
    </condition>
    <condition type="variable" id="expertinstallation">
        <name>setup.type</name>
        <value>expert</value>
    </condition>
    <condition type="java" id="installonwindows">
        <java>
            <class>com.izforge.izpack.util.OsVersion</class>
            <field>IS_WINDOWS</field>
        </java>
        <returnvalue type="boolean">true</returnvalue>
    </condition>
    <condition type="and" id="standardinstallation.onwindows">
        <condition type="ref" refid="standardinstallation"/>
        <condition type="ref" refid="installonwindows" />
    </condition>
</conditions>

Referencing Conditions

Conditions are referenced as optional attributes of several other elements in a installation definition or from IzPack resources:

• as condition attribute

Referencing A Number Of Conditions In One Expression

Simple Expression Language

From IzPack 3.11 on, you don't have to define compound conditions because you can use a simple expression language. The language supports the following operators:

These simple expressions DO NOT follow the usual boolean logic with precedence rules. Instead, they are evaluated left to right in a simple way.

Example:

{{\!conditionA+conditionB+\!conditionC}}

does not equal

{{(\!conditionA) && conditionB && (\!conditionC)}}

but is the same like

{{\!(conditionA && (conditionB && \!(conditionC)))}}

.So you should define complex conditions using the xml structure or use the Complex expression language.

Complex expression language

Beginning with IzPack 5.0, there is also the possibility to use a more complex expression language which evaluates based on boolean precedence rules, which is also reflected in the following table. The higher an operator is, the higher is its precedence.

Example:

{{!conditionA+conditionB+!conditionC}}

equals

{{(!conditionA) && conditionB && (!conditionC)}}

.The complex expression language has been introduced in IzPack 5.0.