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. - Contains Condition
True if certain substring or pattern can be found in a given string, variable content or file content - 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.
Further, IzPack automatically sets reserved conditions depending on the packs selected by the user or an unattended installation (auto-install.xml) to be installed:
izpack.selected.<packname>
where <packname>
is the name attribute of the according pack. If the appropriate pack <pack name="...">
defined in the installation description is selected, the condition validates true. Packs can be selected either in unattended installations by replaying a record of a previous installation (auto-install.xml) or interactively by the user by means of PacksPanel or its derivates, ImgPacksPanel or TreePacksPanel.
Using Conditions
Defining Conditions
<conditions> Element
Conditions are defined in the installation definition as nested <condition>
elements of the <conditions/>
element.
Foe example:
<condition> - Attributes
The following attributes must be set in a <condition> element definition:
Attribute | Usage |
---|---|
| The type of the condition. For built-in types, this is the lowercase portion of the condition class name without condition appended (variable,packselection,java, ...). Custom condition types should be referenced by the full qualified class name, e.g. de.dr.rules.MyCoolCondition. |
| The id of the condition. This will be used to refer to this conditions in other elements |
<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:
^ | an operator for the Xor Conditon |
| an operator for the And Condition |
| an operator for the Or Condition |
| an operator for the Not Condition |
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.
+ | an operator for the And Condition |
| an operator for the Or Condition |
{{}} | an operator for the Xor Condition |
| an operator for the Not Condition |
Example:
{{!conditionA+conditionB+!conditionC}}
equals
{{(!conditionA) && conditionB && (!conditionC)}}
.The complex expression language has been introduced in IzPack 5.0.