JSF 1.2: Invoking a method binding programmatically in Java to add pre- post triggers

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JSF 1.2: Invoking a method binding programmatically in Java to add pre- post triggers

By frank.nimphius | October 29, 2007

On his "Not Yet Documented" example page, Steve did provides tip 122 "Running Custom Backing Bean Code Before/After Default Table Selection Listener", which explained how to call a method binding such that you could add pre- and post- "trigger" codes. An example expression to use this for is the #{bindings.

.collectionModel.makeCurrent} call that by default is set to the ActionListener of an ADF Faces table when using Oracle ADF.

If you want to use your own selection listener instead of #{bindings.

.collectionModel.makeCurrent}, but without loosing the expression's functionality, then Steve's tip becomes quite handy.

However, things have changed between JSf 1.1 (current in JDeveloper 10.1.3) and JSF 1.2 (used in JDeveloper 11) and so have codes:

The helper methods that Steve created for his sample now look as follows in JSF 1.2

PLAIN TEXT

JAVA:

public Object invokeMethodExpression(String expr, Class returnType, Class[] argTypes,Object[] args){
FacesContext fc = FacesContext.getCurrentInstance();
ELContext elctx = fc.getELContext();
ExpressionFactory elFactory = fc.getApplication().getExpressionFactory();
MethodExpression methodExpr = elFactory.createMethodExpression(elctx,expr,returnType,argTypes);
return methodExpr.invoke(elctx,args);
}
public Object invokeMethodExpression(String expr, Class returnType,Class argType, Object argument){
return invokeMethodExpression(expr, returnType,new Class[]{argType}, new Object[]{argument});
}

The reason why this works different is originated in JSF 1.2 and JSP 2.0 using a unified expression language. This however means that before you can use a VlaueBinding or MethodBinding in JavaServer Faces, you have to get a handle to the current - shared - ExpressionFactory being used. Once you have this handle, you can construct and call the MethodBinding. In the case of #{bindings.

.collectionModel.makeCurrent}, the call - from a SelectionListener - in the managed bean looks as

PLAIN TEXT

JAVA:

public void SelectionListener(SelectionEvent selectionEvent) {
// pre-execution code comes next
//#{bindings.DepartmentsView1.collectionModel.makeCurrent}
invokeMethodExpression("#{bindings.DepartmentsView1.collectionModel.makeCurrent}",
Object.class,selectionEvent.getClass(),
selectionEvent);
// post-execution code comes next
}

Please read this.

Frank

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JSF 1.2: Invoking a method binding programmatically in Java to add pre- post triggers