Package org.apache.wicket.util.string.interpolator

Class VariableInterpolator

  • All Implemented Interfaces:
    Serializable, IClusterable
    Direct Known Subclasses:
    MapVariableInterpolator, PropertyVariableInterpolator
    public abstract class VariableInterpolator
extends Object
implements IClusterable
    Base class for variable interpolators. An interpolator substitutes values into a String. So, a variable interpolator substitutes the values of one or more variables into a String.

    The String to interpolate (substitute into) is passed to the VariableInterpolator's constructor. Variables are denoted in this string by the syntax ${variableName}. A subclass provides an implementation for the abstract method getValue(String variableName). The toString() method then performs an interpolation by replacing each variable of the form ${variableName} with the value returned by getValue("variableName").

    "$" is the escape char. Thus "$${text}" can be used to escape it (ignore interpretation). If '$3.24' is needed then '$$${amount}' should be used. The first $ sign escapes the second, and the third is used to interpolate the variable.

    Since:
    1.2.6
    Author:
    Jonathan Locke
    See Also:
    Serialized Form

    • Field Detail

      • string

        protected final String string
        The String to interpolate into

    • Constructor Detail

      • VariableInterpolator

        public VariableInterpolator​(String string)
        Constructor.
        Parameters:
        string - a String to interpolate with variable values

      • VariableInterpolator

        public VariableInterpolator​(String string,
                            boolean exceptionOnNullVarValue)
        Constructor.
        Parameters:
        string - a String to interpolate with variable values
        exceptionOnNullVarValue - if true an IllegalStateException will be thrown if getValue(String) returns null, otherwise the ${varname} string will be left in the String so that multiple interpolators can be chained

    • Method Detail

      • getValue

        protected abstract String getValue​(String variableName)
        Retrieves a value for a variable name during interpolation.
        Parameters:
        variableName - a variable name
        Returns:
        the value