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  1. Tapestry
  2. TAPESTRY-1928

Coercion from null to Boolean yields false instead of null



    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Invalid
    • Affects Version/s: 5.0.6
    • Fix Version/s: None
    • Component/s: tapestry-ioc
    • Labels:


      Boolean has 3 states: null, true, false, but the coercer coerces null to false. While this is correct behaviour for the boolean primitive (which has only 2 states), it is not correct for Boolean.

      The same argument applies here as in TAPESTRY-1648 which dealt with null BigDecimal and Integer.

      A practical consequence is that a BooleanValueEncoder that is 3-value aware becomes useless because the coercer will override it.

      For example I combined a BooleanValueEncoder with Select to allow a user to choose between "", "true", and "false". But when the user chooses "", they unexpectedly get the same result as choosing "false". Here's the template code:

      <select t:id="active" t:type="Select" value="active" model="actives" encoder="booleanValueEncoder"/>

      Here's the relevant java:

      static private final Boolean[] ACTIVES =

      { null, Boolean.TRUE, Boolean.FALSE }

      static private final BooleanValueEncoder BOOLEAN_VALUE_ENCODER = new BooleanValueEncoder();

      public Boolean getActive()

      { return _active; }

      public void setActive(Boolean active)

      { _active = active; }

      public Boolean[] getActives()

      { return ACTIVES; }

      public BooleanValueEncoder getBooleanValueEncoder()

      { return BOOLEAN_VALUE_ENCODER; }

      Here's a BooleanValueEncoder:

      public class BooleanValueEncoder implements ValueEncoder<Boolean> {

      public String toClient(Boolean value)

      { return value == null ? "" : value.toString(); }

      public Boolean toValue(String clientValue)

      { return clientValue.equals("") ? null : Boolean.valueOf(clientValue); }


      When the user chooses "", Tapestry calls setActive(Boolean.FALSE) instead of setActive(null).




            • Assignee:
              hlship Howard Lewis Ship
              geoffcallender Geoff Callender
            • Votes:
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              • Created: