UseAttributeTag.java 文件源码

/**
   * Expose the requested attribute from component context.
   *
   * @exception JspException if a JSP exception has occurred
   */
public int doStartTag() throws JspException
  {
    // Do a local copy of id
  String localId=this.id;
  if( localId==null )
    localId=attributeName;

  ComponentContext compContext = (ComponentContext)pageContext.getAttribute( ComponentConstants.COMPONENT_CONTEXT, PageContext.REQUEST_SCOPE);
  if( compContext == null )
    throw new JspException ( "Error - tag useAttribute : no tiles context found." );

  Object value = compContext.getAttribute(attributeName);
      // Check if value exists and if we must send a runtime exception
  if( value == null )
    if(!isErrorIgnored)
      throw new JspException ( "Error - tag useAttribute : attribute '"+ attributeName + "' not found in context. Check tag syntax" );
     else
      return SKIP_BODY;

  if( scopeName != null )
    {
    scope = TagUtils.getScope( scopeName, PageContext.PAGE_SCOPE );
    if(scope!=ComponentConstants.COMPONENT_SCOPE)
      pageContext.setAttribute(localId, value, scope);
    }
   else
    pageContext.setAttribute(localId, value);

    // Continue processing this page
  return SKIP_BODY;
  }