Home » Author Archives: Oleg Varaksin (page 3)

Author Archives: Oleg Varaksin

Passing complex objects in URL parameters

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Imagine you would like to pass primitive data types, complex Java objects like java.util.Data, java.lang.List, generic classes, arrays and everything what you want via URL parameters in order to preset default values on any web page after the page was loaded. Common task? Yeah, but available solutions are mostly restricted to encoding / decoding of java.lang.String. The approach I will ...

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JSF – Eager CDI beans

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Everybody knows eager managed beans in JSF 2. @ManagedBean has an eager attribute. If eager=’true’ and the scope is application, then this bean must be created when the application starts and not during the first reference to the bean. This is a nice feature when you want to load application scoped data (e.g. some select items for menus) during application ...

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GET / POST with RESTful Client API

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There are many stuff in the internet how to work with RESTful Client API. These are basics. But even though the subject seems to be trivial, there are hurdles, especially for beginners. In this post I will try to summarize my know-how, how I did this in real projects. I usually use Jersey (reference implementation for building RESTful services). See ...

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Configure timeout for CDI conversations

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CDI conversation scope is a nice feature when developing JSF applications. Imagine you have large data tables which take a long time to be loaded. You normally don’t want to place the loaded data in session scoped beans by reason of high memory consumption. And you can’t place the loaded data in view scoped beans because you wouldn’t like always ...

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JSF Event-based communication: New-school approach

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In the last post, we learnt event-based communication on basis of Observer / Event Listener and Mediator patterns. Due to their shortcomings I would like to show more efficient ways for event-based communication. We will start with Google Guava EventBus and end up with CDI (Contexts and Dependency Injection for the Java EE platform). Guava EventBus Google Guava library has ...

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JSF Event-based communication: Old-school approach

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Web applications written in JSF consist of beans which interact among each other. Communication between beans is one of the main design patterns when developing a web application. Sometimes, one bean need to send events to other beans to inform them about some changes or whatever else. We can normally inject a managed or Spring bean into the property of ...

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Dynamic forms, JSF world was long waiting for

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The new PrimeFaces Extensions release 0.5.0 brought a new DynaForm component. Normally, we can build a form quite straightforward by h:panelGrid oder p:panelGrid if the count of rows / columns, positions of elements, etc. are known. That’s true for static forms. But it’s not possible to use h:panelGrid oder p:panelGrid if a form is described dynamically, at runtime. E.g. if ...

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Custom JSF validator for required fields

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JSF components implementing EditableValueHolder interface have two attributes ‘ required’ and ‘ requiredMessage’ – a flag indicating that the user is required to input / select not empty value and a text for validation message. We can use that, but it’s not flexible enough, we can’t parameterize the message directly in view (facelets or jsp) and we have to do ...

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High Performance Webapps – Data URIs

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I continue to write tips for perfomance optimization of websites. The last post was about jQuery objects. This post is about data URIs. Data URIs are an interesting concept on the Web. Read ” Data URIs explained” please if you don’t know what it does mean. Data URIs are a technique for embedding resources as base 64 encoded data, avoiding ...

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JSON with GSON and abstract classes

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I have switched to Google Gson after many years of using org.json library for supporting JSON data interchange format in Java. org.json is a lower-level library, so that you have to create JSONObject, JSONArray, JSONString, … and do other low-level work. Gson simplifies this work. It provides simple toJson() and fromJson() methods to convert arbitrary Java objects to JSON and ...

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