Sometimes it could be handy to apply view criteria dynamically at run time. Let's say I have a simple VO EmployeesView representing data from Emloyees table in HR schema. The VO has view criteria SalaryCriteria:
The criteria filters records with some salary value using bind variable "salary". On my jspx page I have a table , inputText for salary value and a button:
By default the VO doesn't have any view criteria applied, but when the button is pressed, SallaryCriteria is to be applied with submitted value for salary bind variable. The button's action listener actually calls very simple method in EmployeesViewImpl class:
The criteria filters records with some salary value using bind variable "salary". On my jspx page I have a table , inputText for salary value and a button:
By default the VO doesn't have any view criteria applied, but when the button is pressed, SallaryCriteria is to be applied with submitted value for salary bind variable. The button's action listener actually calls very simple method in EmployeesViewImpl class:
public void applySalaryCriteria(Number salary) {
setsalary(salary);
setApplyViewCriteriaName("SalaryCriteria");
executeQuery();
}
In this use-case I don't have any af:query component on my jspx page and all the job of applying view criteria is going to be done in the model layer.
But there is another use-case when I have af:query on a page and I need to change selected criteria in af:query's component programmatically at run time. In my managed bean I have the following piece of code:
private RichQuery queryPnl; //Bounded af:query
//Looking for query descriptor in a list with specified query name
private QueryDescriptor getQueryDescriptor(List<QueryDescriptor> list, String queryname) {
QueryDescriptor result = null;
for (Object qd: list.toArray())
if (((QueryDescriptor) qd).getName().equals(queryname)) result = (QueryDescriptor) qd;
return result;
}
//Selecting criteria with specified name
private void selectCriteria(String criteria) {
QueryModel model = queryPnl.getModel();
//Looking for needed query decriptor
QueryDescriptor qd = getQueryDescriptor(model.getSystemQueries(),criteria);
//Setting needed query descriptor as current one
queryPnl.setValue(qd);
model.setCurrentDescriptor(qd);
}
So, when I need to change selected criteria I call selectCriteria method with specified criteria name. And if I need to apply the criteria and execute the query I call applyCriteria method:
private void applyCriteria(QueryDescriptor qd) {
//Creating new QueryEvent
QueryEvent queryevent = new QueryEvent(queryPnl, qd);
//And processing this event
//EmpCriteriaQuery is ID attribute of the searchRegion tag in the pageDef
invokeMethodExpression("#{bindings.EmpCriteriaQuery.processQuery}",
Object.class, new Class[]{QueryEvent.class}, new Object[]{queryevent});
}
//Just utility method to invoke EL expressions
public Object invokeMethodExpression(String expr, Class returnType, Class[] argClasses, Object[] arguments){
FacesContext fc = FacesContext.getCurrentInstance();
ELContext elc = fc.getELContext();
ExpressionFactory exprFactory = fc.getApplication().getExpressionFactory();
MethodExpression methodExpr = exprFactory.createMethodExpression(elc,expr,returnType,argClasses);
return methodExpr.invoke(elc,arguments);
}
That's all!
