Salient Soft

Update 26/7/2011

Some more points that were omitted or incorrect in the first posting:-

• A handy feature with templates/custom tags is that you can render children of the template/tag at the call site simply by using a <ui:insert> without a name. You therefore do not need to use a <ui:define> tag in this case, and all children which are not contained in other <ui:define> or <ui:param> tags will be rendered as part of this default <ui:insert>
• The statement below that it is not possibly to insert a number of different markup variants in a composite component is incorrect. A composite component can have a number of named facets just like a ‘real’ JSF component, and these allow markup to be inserted in the same way as <ui:insert>/<ui:define> does for a template or custom tag.

Original Post

I had a complex decorator which was used for tree browsing. It had a number of ui:inserts for custom markup, plus also a large number of <ui:params> to define EL parameters used within it.

This all worked fine, and even looked quite tidy as all the <ui:params> were listed one per line below each other. However, it was all rather verbose compared to using a custom tag where you would use attributes instead to pass the EL parameters.

It turns out that you can convert a decorator to be a custom tag with no effort as they operate similarly. You merely need to register the xhtml file in a taglib as with any custom tag, and you can then call exactly the same code as a custom tag instead of a decorator.

The neat tricks here are that:-

• <ui:params> become attributes which are less verbose, but the tag itself does not know any difference and needs no changes.
• <ui:insert>/<ui:define> work perfectly with a custom tag exactly as they do with a decorator.

Another nice point on this is you can develop custom tags that include pseudo ‘child markup’ in similar fashion to composite components, by using the <ui:define>s. Providing you do not need the other features of composite components such as retargeting, Ajax etc., custom tags can be very useful where you have a need to insert a number of different markup variants for different flavours of the tag, as you cannot do this so flexibly with a composite component.

The technique of using <ui:inserts> in a custom tag is hinted at somewhat obliquely in Core Javaserver Faces, 3rd Edition, on P196 in the listing of the planet custom tag, which contains a <ui:insert> called content1.

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I have sometimes had a need to define temporary variables for use on a facelets page.

When I tried using <c:set> for this it failed to work when used within a decorator.

However, <ui:param> fulfills the need admirably. Whilst it is normally used to pass EL parameters to a template from its client, it can also be used to hold data for use elsewhere in the same decorator for example. Bear in mind that there are scoping issues which as yet I have not fully bottomed out – the variable is probably visible anywhere else in other templates/xhtml files on the same page and so care is needed with naming.

A good example of this was when I wanted to define a couple of size parameters (which could not be done with CSS) at the top of a decorator/custom tag where they were clearly visible, and then re-use them multiple times further down in tag attribtutes to called tags.

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There appears to be an issue when using EL in child components included in a composite component using <composite:insertChildren>

I am already using this technique for the tableCC component, to insert the columns as children, and the child columns have plenty of EL in them which is not passed to tableCC, as well as having custom tags as columns. However, there appears to be an issue when this technique is used in nested composite components.

When I tried this, I found that any EL expressions in the child components is evaluated as late as possible in the context of the called composite component, not the caller!

This means that if you need to refer to an attribute passed in to the caller of the CC, you must pass that attribute on to the CC as well as referring to it in the child components, as their EL will be evaluated in the CC not the caller.

Providing you do this, it all works fine. However, the issue with this is that it will tend to break encapsulation of the interface to the child nested CC – you have to change its interface depending on what EL you want to use in the child components passed to it.

This was unacceptable to me, so I switched to a different technique. Instead, my base component (actually a flexible icon/base button using p:commandLink) became a custom tag, and I used facelets <ui:inserts> to handle the insertion of custom markup. I then wrapped composite components around this to provide the necessary custom markup.

The reason for going down this route was that I have had issues with glitchy ajax updates on standard Primefaces buttons at small sizes (see this Mantis issue). Also I was crafting icon buttons with multiple jQuery icons on them, using CSS to position them accurately. This was tricky with a p:commandButton and involved introducing CSS that I was concerned may need change in future releases, so I went my own way when using highly custom buttons and buttons at small sizes.

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This can be done e.g. by a Facelets Decorator using <ui:insert> and I have used this in a number of places.

However, in one case, I wanted to make a complex treeBrowser custom tag switchable between editable mode and readonly using just a single flag passed as an attribute. Note that I did not want to switch it dynamically at run time – I just re-used the tag in a number of places and some were editable and some were not. As this switch involved a number of changes in the tag, it was convenient to drive them all from a single flag.

In addition, whilst I could have used a decorator for this, I already had 2 versions of the tag each decorating a base version, where each version was used to browse completely different tree structured data in the application which was all handled polymorphically.  Using decorators for readonly/editable as well would have multiplied up the variants to 4, which was undesirable. By using a single EL flag, I was able to make all the switching entirely in the base custom tag which was a real help here.

Anyway – to discuss the real point of the post – to achieve my goal I needed to conditionally include columns for a <p:dataTable>. Using <ui:fragment> to do this does not work as <ui:fragment> creates a new component in the JSF tree which is not a column, and <p:dataTable> ignores any children that are not columns. Whilst there are ways using composite components to indicate with interface properties the precise Class type that the component appears to be, fooling <p:dataTable> by making it look like a column does not work – I tried this and it failed, and there are posts on the Primefaces forum citing the same issue.

The simple solution was to use <c:if> to conditionally include columns. This eventually worked correctly, once I had fixed a particularly nasty incorrect JSTL namespace issue which is fully described in this post here.

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It is useful to be able to pass an enum rather than a string value as this introduces additional error checking by JSF.

JSF has a built in enum converter, so that all you need to do is pass a literal string which must then be one of the enum fields. JSF detects that the method argument is an enum and does the appropriate conversion and error checking. This will not occur until run time, but you will at the very least get a JSF error on your browser page and in the log, for example:-

javax.faces.el.EvaluationException: java.lang.IllegalArgumentException:
   No enum const class uk.co.salientsoft.view.Workspace$PageType.LOGOUT

See here for the StackOverflow post detailing this issue  – BalusC to the rescue again!

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As I am running a Java development machine I want precise manual control of the versions of Java and all the related tools.

The Java auto updater runs regularly and nags about updating, but I want to turn it off. There is a control panel applet  – “Java (32-bit)” – with an option under the updates tab to do this, however it does not work – if you uncheck the “check for updates automatically” tick box, it appears to save OK but when you close and re-open the applet and look again the value has not changed.

This is due to an apparently long standing Java bug – it does not run with admin privileges and so cannot change the value. It would be nice if it gave an error telling you that it did not work due to a permissions problem, but unfortunately it just fails completely silently.

This post here outlines various solutions to the problem. The accepted answer, which worked for me, is to find javacpl.exe, right click it, and run with admin privileges. The location of it in my case was not where the post suggested, even though I had done a default install, so you will probably need to search for it. In my case I had a couple of versions of it, one was for an old version of Java. The path for mine which I used successfully was C:\Program Files (x86)\Java\jre6\bin

This fixed the problem, and upon reopening the control panel applet (with or without admin privileges) the box was unticked.

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Primefaces uses the theming capability of jQuery, including the ability to create your own themes using ThemeRoller. This powerful facility separates theme specific CSS from structural CSS which defines the layout of UI components such as tables. At the time of writing, Primefaces has 32 different themes. It does also have a themeSwitcher component, but this has some issues which make it less than ideal for many environments. In addition, the structure of the themes has changed as of version 2.2 – they are now deployed in jars rather than as bare resource files. The following lists the salient issues and desirable features regarding the theme switcher:-

• When switching themes, rather than using a theme deployed with the application, the Primefaces themeSwitcher downloads the new theme from the internet and installs it directly, which is undesirable in many environments.
• Ideally, as well as using the themes deployed with the application, the themeSwitcher should be configurable dynamically to allow new themes to be easily added.
• The theme switcher should also, as far as possible, derive its theme list presented to the user dynamically from the themes that have actually been deployed. Failing this, it should be possible to configure this list as a deployment configuration option, i.e. in web.xml
• It would be desirable to isolate the theme Switcher from any further changes to the Primefaces theming structure. For example, if a plug-in architecture is used, a new theming interface can be incorporated simply by adding a new plug-in.

The Theme Manager attempts to address all of the above issues to provide a flexible and upgradeable solution to Primefaces theming. The Theme Manager including PDF documentation will be found  in the repository here.

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This utility was developed to allow JSF and Java software to dynamically manage dependency issues caused by interface changes across differing versions of dependant libraries, by querying the utility at runtime with rule based match checks about the versions actually deployed. Typically interfaces to software are consistent for a range of versions, and then change whereupon they remain the same for a further range of versions. The Version
Manager thus allows rule based checks to match a contiguous range of versions, as well as matching a single specific version.

The utility was developed in response to issues caused by changes between Primefaces versions. A particular case in point was that some custom Javascript and CSS was implemented for V2.2.M1 to fix common issues concerning header alignment and column width for scrolling tables. These changes were encapsulated in .css and js files in a TableCC composite component which decorates the standard Primefaces p:dataTable.
These fixes of necessity used css and jQuery selectors referring to underlying Primefaces structural css classes – this exposes such code to risk of change, but in this case the risk was justified as the code was there to fix issues.

The css in Primefaces changed late on in the V2.2 cycle – the class names changed and the HTML was simplified to remove a div container layer. These changes broke the above code. It was felt that this would in general not be an isolated issue. Primefaces is a fast moving development project, which has its upsides in that new features and new versions come onstream regularly. The downside in a fast moving environment can be issues such as the
above one. In fairness to Primefaces, it is very difficult to develop a generic Table component using current HTML standards which allows fixed column headers with a scrolling data table. Some things such as dynamic resizing of columns just cannot play ball in the current scenario, and scroll bars coming and going with different data volumes add further challenges of their own! In practice it is not possible to cover every possible use case. My approach is to narrow down a particular set of use cases I need to work with, and then come up with the necessary fixes/decorator components as above to handle those particular use cases.

In order to mitigate the effect of this kind of issue when versions change, and to avoid proliferation of a number of different code versions each matched to a set of dependant library (e.g. Primefaces) versions, a Version  Manager facility was developed.

The Version Manager including PDF documentation and an example may be found in the repository here.

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With JSF 2.0, it is now possible to use any class as an item in a selectOneMenu combo and related components. This is described in  “Core JavaserverFaces” p157ff. However, the book does not mention that you also need a custom JSF converter to convert between object and string.

If you then implement a custom converter as in the book on p279, e.g. with:-

<h:selectOneMenu styleClass="ss-tsw-select" id="cmbTheme"
      value="#{themeSwitcherBean.theme}" disabled="#{themeSwitcherBean.selectDisabled}"
      converter="uk.co.salientsoft.thememanager.ThemeConverter"
      immediate="true" onchange="submit()">

CDI fails to inject any references used in the converter class, as JSF 2 does not allow CDI in converters, as detailed in this Stack Overflow Post.

It does work however if you use an EL reference in the converter attribute as mentioned in this post here.

Note that the post indicates that it may require it to be an application scoped bean. In my case, it worked fine as both a request scoped and application scoped bean with no trouble. I also removed the @FacesConverter("uk.co.salientsoft.thememanager.Theme") annotation as this was no longer required due to the EL reference. The post indicates that this is perceived to be more untidy due to the use of EL and a managed bean, but I cannot see an issue with this. I cannot see why converters cannot be application scoped CDI beans, it all fits in fine. Here is the code fragment above, modified to use an EL reference instead:-

<h:selectOneMenu styleClass="ss-tsw-select" id="cmbTheme"
      value="#{themeSwitcherBean.theme}" disabled="#{themeSwitcherBean.selectDisabled}"
      converter="#{themeConverter}"
      immediate="true" onchange="submit()">

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I had issues getting Activesync to connect over bluetooth during the last few days. at each attempt activeSync on the HTCgave the error “attention required, unable to connect, bluetooth port may be in use” etc.

I tried restarting both and reconnecting but this did not work.

On one occasion, Window 7/panther was unable to complete listing the devices, but this appears to have been a one of as it is fine today.

In the end, I tried deleting the pairing and repairing the devices. This solved the problem. I was concerned that it would also delete activesync related info and require reconfiguration of that, but it did not. Once the pairing was set up, I was able to connect via Bluetooth from the HTC and resync correctly with no further errors.

I have seen this before in other situations where a bluetooth pairing appears to get corrupted in someway, and generally as in this case deleting the pairing and repairing seems to resolve it.

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