Tuesday, May 1, 2012

EJB Named Criteria - Apply bind variable in Backingbean

EJB Named criteria are predefined and reusable where-clause definitions that are dynamically applied to a ViewObject query. Here we often use to filter the ViewObject SQL statement query based on Where Clause conditions.

Take a scenario where we need to filter the SQL statements query based on Where Clause conditions, instead of playing with SQL statements use the EJB Named Criteria which is supported by default in ADF and set the Bind Variable parameter at run time.

You can download the sample workspace from here
[Runs with Oracle JDeveloper 11.1.2.0.0 (11g R2) + HR Schema]

Implementation Steps

Create Fusion Web Application with entity based on Employees table, then create a session bean and data control for the session bean.

Open the DataControls.dcx file and create sparse xml for as shown below.


In sparse xml navigate to Named criteria tab -> Bind Variable section, create binding variable deptId.


Now create a named criteria and map the query attributes to the bind variable.


In the ViewController create index.jspx page, from data control palette drop employeesFindAll->Named Criteria->EmployeesCriteria->Table as ADF Read-Only Filtered Table and create the backingBean as "IndexBean".

Open the index.jspx page and remove the "filterModel" binding from the table, add <af:inputText />, command button and bind them to backingBean. For command button create the actionListener as "applyEmpCriteria" and add below code to the file.

public void applyEmpCriteria(ActionEvent actionEvent) {
   DCIteratorBinding dc = (DCIteratorBinding)evaluteEL("#{bindings.employeesFindAllIterator}");
   ViewObject vo = dc.getViewObject();
   vo.applyViewCriteria(vo.getViewCriteriaManager().getViewCriteria("EmployeesCriteria"));
   vo.ensureVariableManager().setVariableValue("deptId", this.getDeptId().getValue());
   vo.executeQuery();
}

/**
 * Programmtic evaluation of EL
 *
 * @param el EL to evalaute
 * @return Result of the evalutaion
 */
public Object evaluteEL(String el) {
 FacesContext fctx = FacesContext.getCurrentInstance();
 ELContext elContext = fctx.getELContext();
 Application app = fctx.getApplication();
 ExpressionFactory expFactory = app.getExpressionFactory();
 ValueExpression valExp = expFactory.createValueExpression(elContext, el, Object.class);
 return valExp.getValue(elContext);
}
Run the index.jspx page, enter departmentId value as 90 and click in ApplyEmpCriteria button. Now the bind variable for the Named criteria will be applied at runtime in the backing bean and it will re-execute ViewObject query to filter based on where clause condition.

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