code: @Override
      public void execute() throws BuildException {
          if (ifCondition != null) {
              final String msg = MessageUtils.getMessage("DOTA014W", "if", "if:set")
                      .setLocation(this.getLocation())
                      .toString();
              getProject().log(msg, Project.MSG_WARN);
          }
          if (unlessCondition != null) {
              final String msg = MessageUtils.getMessage("DOTA014W", "unless", "unless:set")
                      .setLocation(this.getLocation())
                      .toString();
              getProject().log(msg, Project.MSG_WARN);
          }
          final boolean fail = nestedConditionPresent()
                         ? testNestedCondition()
                         : (testIfCondition() && testUnlessCondition());
          if (!fail) {
              return;
          }
  
          if (id == null) {
              throw new BuildException("id attribute must be specified");
          }
  
          final MessageBean msgBean = MessageUtils.getMessage(id, readParamValues());
          final DITAOTLogger logger = new DITAOTAntLogger(getProject());
          if (msgBean != null) {
              final String type = msgBean.getType();
              if (FATAL.equals(type)) {
                  setMessage(msgBean.toString());
                  try {
                      super.execute();
                  } catch (final BuildException ex) {
                      throw new BuildException(msgBean.toString(),new DITAOTException(msgBean, ex, msgBean.toString()));
                  }
              } else if (ERROR.equals(type)) {
                  logger.error(msgBean.toString());
              } else if (WARN.equals(type)) {
                  logger.warn(msgBean.toString());
              } else if (INFO.equals(type)) {
                  logger.info(msgBean.toString());
              } else if (DEBUG.equals(type)) {
                  logger.debug(msgBean.toString());
              }
          }
  
          
      }
docs: Task execute point.
  @throws BuildException exception
  @see org.apache.tools.ant.taskdefs.Exit#execute()