Refactoring puzzler: how to remove duplication here?

ZuperDao

      StringBuilder whereConstraints = new StringBuilder();
      if (!isEmpty(typesActu)) {
         whereConstraints.append(" AND a.type_id IN (?) ");
      }
      if (!isEmpty(newsletters)) {
         whereConstraints.append(" AND (ap.profils_id IN (?) OR ap.profils_id IS NULL)");
      }
      if (!isNullOrEmpty(term)) {
         whereConstraints.append(" AND (titre LIKE (?) OR texte_complet LIKE(?) ) ");
      }
      whereConstraints.append(" AND date_publication IS NOT NULL ");
      if (beginDate != null) {
         whereConstraints.append(" AND date_publication >= ?");
         if (endDate != null) {
            whereConstraints.append(" AND date_publication <= ?");
         }
      }
      String limitClause = "";
      if (limit != null) {
         limitClause += " LIMIT ?";
      }

      final String sql = BASE_QUERY + whereConstraints.toString() + ORDER_BY_CLAUSE + limitClause;

      return new PreparedStatementCreator() {
         @Override
         public PreparedStatement createPreparedStatement(Connection connection) throws SQLException {
            PreparedStatement statement = connection.prepareStatement(sql);
            int position = 1;
            if (!isEmpty(typesActu)) {
               statement.setString(position++, concatActuTypes(typesActu));
            }
            if (!isEmpty(newsletters)) {
               statement.setString(position++, concatNewsTypes(newsletters));
            }
            if (!isNullOrEmpty(term)) {
               String likeTerm = "%" + term + "%";
               statement.setString(position++, likeTerm);
               statement.setString(position++, likeTerm);
            }
            if (beginDate != null) {
               statement.setString(position++, beginDate.toString("yyyy-MM-dd"));
               if (endDate != null) {
                  statement.setString(position++, endDate.toString("yyyy-MM-dd"));
               }
            }
            statement.setInt(position, limit);
            return statement;
         }
      };

Types de typesActu, newsletters, concatActuTypes, concatNewsTypes ? Ce sont / Ça traite des collections ? isEmpty et isNullOrEmpty ça vient de Guava ?

Une possibilité pour le premier bloc. On part avec trois méthodes :

public <T> String getWhenExists(Iterable<T> iterable, String value) {
    return isEmpty(iterable) ? "" : value;
}

public String getWhenExists(String string, String value) {
    return isNullOrEmpty(string) ? "" : value;
}

public String getWhen(boolean isTrue, String value) {
    return isTrue ? value : "";
}

Et on replace tout le premier bloc par :

    final String sql = new StringBuilder()
            .append(BASE_QUERY)
            .append(getWhenExists(typesActu, " AND a.type_id IN (?) "))
            .append(getWhenExists(newsletters, " AND (ap.profils_id IN (?) OR ap.profils_id IS NULL)"))
            .append(getWhenExists(term, " AND (titre LIKE (?) OR texte_complet LIKE(?) ) "))
            .append(" AND date_publication IS NOT NULL ")
            .append(getWhen(beginDate != null, " AND date_publication >= ?"))
            .append(getWhen(beginDate != null && endDate != null, " AND date_publication <= ?"))
            .append(ORDER_BY_CLAUSE)
            .append(getWhen(limit != null, " LIMIT ?")).toString();

Et je crois qu'à partir de Java 6, tu peux utiliser directement concaténations de chaînes à la place du StringBuilder. Il y a une conversion qui est faite directement.