def ';' KEY (';' STRING)?

Summary

The def macro looks up a property by key and returns its value, or returns a default value if the property is not set. The default is an empty string if not specified.

Syntax

${def;<key>[;<default>]}

Parameters

• key - The property name to look up
• default (optional) - Value to return if property not set (default: empty string)

Behavior

• Looks up property by key
• Returns property value if set
• Returns default if property not set
• Default is empty string if not specified
• Handles undefined properties gracefully

Examples

Get property with default:

${def;version;1.0.0}
# Returns property value or "1.0.0" if not set

Empty default:

${def;optional.setting}
# Returns property value or "" if not set

Use in paths:

output.dir=${def;custom.dir;target}

Conditional with default:

${if;${def;debug.mode;false};debug-on;debug-off}

Use Cases

• Providing default values
• Optional properties
• Configuration fallbacks
• Safe property access
• Avoiding undefined property errors

Notes

• Safer than direct property reference
• Default prevents empty/undefined issues
• Unlike ${key}, returns default instead of literal
• Empty string is valid default
• See also: ${get} for list element access
• See also: ${if} for conditional defaults

See test cases in MacroTestsForDocsExamples.java