JSF 2.x Tip of the Day: Programmatically Creating EL ValueExpression

A common need is to create a ValueExpression for use in binding a JSF component attribute to a value in the JSF/CDI managed beans.

This is a convenience method that I have created to create these expressions.

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/**  * Creates a {@link ValueExpression} that wraps an object instance. This  * method can be used to pass any object as a {@link ValueExpression}. The  * wrapper {@link ValueExpression} is read only, and returns the wrapped  * object via its {@code getValue()} method, optionally coerced.  *  * @param expression The expression to be parsed.  * @param expectedType The type the result of the expression will be coerced  * to after evaluation.  * @return The parsed expression.  */ public static ValueExpression createValueExpression(String expression, Class<?> expectedType) {     FacesContext context = FacesContext.getCurrentInstance();     return context.getApplication().getExpressionFactory()             .createValueExpression(context.getELContext(), expression, expectedType); }

Here is an example of how to use it.

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1 2	UICommandLink clink = (UICommandLink) application.createComponent(UICommandLink.COMPONENT_TYPE); clink.setValueExpression("value", createValueExpression("#{indexBean.columnHeader}", String.class));

In this example I bind the <h:commandLink/> value programmatically to the @ManagedBean called IndexBean value called columnHeader.