Bit #18 - Dynamically changing the View Object's query WHERE clause

You can dynamically change the View Object's (VO) query WHERE clause by overriding the buildWhereClause() VO method. When doing so, ensure that you call the base class' buildWhereClause() first, to let the framework do its processing before making your own changes. The StringBuffer parameter that is passed to the method is the complete query SQL statement. Do your changes directly onto it. When done, make sure that you return appropriately a true/false boolean to indicate whether a WHERE clause was appended to the query or not. Here is an example.

Example:


    @Override
    protected boolean buildWhereClause(StringBuffer sqlBuffer, int noBindVars) {

        // call ViewObjectImpl's buildWhereClause() to allow the framework to do its processing
        boolean hasWhereClause = super.buildWhereClause(sqlBuffer, noBindVars);

        if (hasWhereClause) { // framework added a WHERE clause
            // modify the WHERE clause as needed
        }
        else { // framework did not add a WHERE clause, so we need to add it ourselves
            // add a WHERE clause here
            hasWhereClause = true; // ensure that is set to notify the framework
        }

        return hasWhereClause; // return true/false to indicate whether a WHERE clause was added
    }


Context:

View Object Implementation

Bit #17 - Using the securityContext bean in a JSF page

To acess the user's authentication information from within a JSF page, use the securityContext bean and any of its available methods. For instance, using Expression Language (EL), the following will return true/false indicating whether the user is authenticated or not: #{securityContext.authenticated}. Similarly, to determine whether the user has been assigned a specific role, use the following EL snippet #{securityContext.userInRole['SomeRole']}. It will return true if the user has been assigned the specific role.


Example:

    // in the context of a JSF page

    <af:commandLink id="login_logout" action = "#{securityContext.authenticated ? 'logout' : 'login'}" text="#{securityContext.authenticated ? 'Logout' : 'Login'}/>

    <af:commandToolbarButton id="delete"  actionListener="#{backingBean.delete}" disabled="#{securityContext.userInRole['CanDelete']==false}" text="Delete"/>


Context:

JSF Page

Bit #16 - Removing a row from a query collection without deleting it from the database

There are times when you want to remove a row from a query collection (the query result) without actually removing it from the database. The query collection - oracle.jbo.server.QueryCollection - gets popullated each time the View is executed - when the View's associated query is run, and represents the query result. While the Row.remove() will remove the query collection row it will also remove the underlying Entity row - for an Entity-based View - and post a deletion to the database. If your programming task requires that the row is removed from the query collection only, i.e. removing a table row in the UI without actually posting a delete to the database, use the Row method removeFromCollection() instead. Just be aware that each time the View is re-executed the Row will show up once again!

Example:

        // in the context of the ApplModuleImpl

        // remove the current row from the query collection
        EmployeesRowImpl employee = (EmployeesRowImpl)(this.getEmployees().getCurrentRow());
        employee.removeFromCollection();

        // the employee row has been removed from the result set and cannot be used anymore


Context:

Application Module Implementation Class
View Object Implementation Class

Bit #15 - Using a Key to locate a Row in a View Object, Pt. 2

Instead of using the findByKey() method to locate a number of rows in the View Object identified by a Key attribute - explained in Bit #14 - Using a Key to locate a Row in a View Object, you can use the View Object getRow() method supplying the Key as an argument. This method will return the Row identified by the Key supplied as an argument to it. An example follows.

Example:

    // in the context of the ApplModuleImpl

    // locate the employee's department
    Number departmentId =
        ((EmployeesRowImpl)(this.getEmployees().getCurrentRow())).getDepartmentId();
    Key keyDepartment = new Key(new Object[] { departmentId });

    // get the department based on the department identifier
    DepartmentsRowImpl department =
        (DepartmentsRowImpl)this.getDepartments().getRow(keyDepartment);

    if (department != null) {
        // you can access the Department's attributes here....
    }



Context:

Application Module Implementation Class
View Object Implementation Class