There are several migration steps to do, dependent on the application you want to migrate. The steps can be classified by

- Tag library
- Java API
- CSS
- JavaScript
- External components (for Java, CSS, Javascript)

Most of these steps are relatively simple to carry out. Just replace "this" with "that" and so on. Some of them can be done with regular expressions.

JavaServer Pages are no longer supported. You need to migrate to Facelets as VDL. You may do that before migrating to Tobago 3.

`<tx:in label="a" fieldId="b" id="c" />` will be transformed to `<tc:in label="a" id="c" />`. The id of the input element in HTML is id="c::field".

There is a little conflict between the "label" attribute used in the JSF spec. and the Tobago tx: label: Tobago means it should be displayed, and JSF spec. means that this should be used to display messages. In most cases there is no issue for that. But for the case that the application need a message label, but should not be displayed we need a new attribute:

(preliminary) "labelPosition" or "labelLayout" with value "none" With this attribute we may advise the renderer also the position of the label. Or, using an attribute "renderLable"...

You need to set the `<f:convertDateTime type="time"\/>` inside the `<tc:date/>`. Replace all `<tc:cell/>` with `<tc:panel/>`. Dependent of the used layout manager, these tags may be dropped completely.

The layout managers are no longer a facet of a container. They are in the tree hierarchy explicitly.

Old:

    <tc:panel>
      <f:facet name="layout">
        <tc:flowLayout/>
      </f:facet>
      ... content ...
    </tc:panel>

New:

    <tc:flowLayout>
      ... content ...
    </tc:flowLayout>

`<tc:image/>` has no longer the attributes `width` and `height`, please use a `<tc:style/>`child tag instead. tc:column with f:facet name="dropDownBox" can now easily and much more flexible implemented with the header facet of the tc:sheet. Example: The Menu tags tc:menu, tc:menuBar, tc:menuCommand and tc:menuSeparator are no longer available and needs to be migrated to tc:links or tc:bar or tc:buttons with tc:link and tc:separator inside. The popup was implemented new, using a general concept of collapsible in Tobago. This tag is removed. The tc:popup tag is no longer a facet of a command. The tag can be put anywhere on the page. The open/close commands now can be used flexible Example: Replace `<f:facet name="action">` with `<tc:event event="load">` The `<f:facet name="change">` and the attribute `renderedPartially` are replaced by `<f:ajax>`, use `<tc:event>` instead of `<tc:command>` Class is no longer present, you should use a JSF 2 exception handler instead. The API of the RendererBase class has changed a bit. Also the automatic renderer selection has been dropped. If you write your own renderer for existing classes, you now need to register it in the faces-config.xml as ususal in JSF.

To have typesafe code many Java classes to provide constants are migrated to Java enums, e. g. `org.apache.myfaces.tobago.component.Attributes`.

Tobago 3 uses the great CSS library. Currently in version 4.0.0-alpha.5. Because of the use of the Bootstrap lib, some Tobago CSS classes are no longer needed, and has been Changed from content-box to border-box. Tobago 3 requires Servlet API 3.0. Tought the file upload uses `javax.servlet.http.Part` instead of `org.apache.commons.fileupload.FileItem`. You no long need to define a TobagoMultipartFormdataFilter in the web.xml.

There is no longer a tobago-fileupload.jar.

Remove the dependency to commons-fileupload.jar in your web app, if there is any.

If using JSF 2.0 or 2.1 you will need to add a tag `<multipart-config>` Tag to the FacesServlet config in the `web.xml`. Since JSF 2.2 this is not needed. Example:

      TODO:

        Because of the changed layout model (no longer on the server, but with browser CSS) there a some
        classes, methods and parameters removed.

        * AbstractUIPage.getActionPosition()

        * AbstractUIPage.setActionPosition()

        * class Box

        * class Dimension

        * class Position

        * ClientProperties.pageWidth

        * ClientProperties.pageHeight

        * <tc:gridLayoutConstraint> -> <tc:span> (only for attributes columnSpan and rowSpan)

        * <tc:gridLayoutConstraint> -> <tc:style> (all other attributes)

        * <tc:toolBar> -> <tc:buttons>
        * <tc:toolBarCommand> -> <tc:button>

        * If using <tc:page> with the attributes state, width, height: remove the attributes

        * TODO: use ExternalContext.redirect instead of AjaxUtils.redirect

        * Replace AjaxUtils.getRequestPartialIds() with
        FacesContext.getPartialViewContext().getExecuteIds() or
        FacesContext.getPartialViewContext().getRenderIds() respectively.

        * TODO: Move data from ClientProperties to TobagoContext

        * TODO: Replace <tc:columnEvent> with <tc:row>

        <tc:mediator> removed

        If you need a Tobago component to set e. g. some style in a renderer as a replacement,
        use a simple <tc:panel>.

        Tango Icons

        Tango icon lib is no longer part of Tobago. Replaced by Font Awesome. If you need it, please
        include it in the application.

        Dependencies to JS/CSS libs: jQuery UI

        Tobago uses the jQuery UI library. The library is customizable to limit the amount of JS and CSS content.
        You will find the used modules in the header of each jQuery UI file.

        * E. g. Tobago 2.0.10 contains jQuery UI 1.10.4 with these contents:

        * jquery.ui.core.js

        * jquery.ui.widget.js

        * jquery.ui.mouse.js

        * jquery.ui.position.js

        * jquery.ui.draggable.js

        * jquery.ui.datepicker.js

        * jquery.ui.slider.js

        * jquery.ui.core.css

        * jquery.ui.datepicker.css

        * jquery.ui.slider.css

        * jquery.ui.theme.css

        * Tobago 3.0.0 contains jQuery UI 1.12.1 with this component:

        * widget.js

        If you are using jQuery UI directly, you may add the required resources via the tobago-config.xml
          and exclude the jQuery UI resource that comes with Tobago.