Use an SQL Query in a backing bean

Question

hi,
I like to know how to run an SQL query in a backing bean method, this being the code I tried , his goal is to fill the field "cin" with data coming from my database, here is the Code:
public String cb2_action() {
BindingContainer bindings = getBindings();
OperationBinding operationBinding = bindings.getOperationBinding("CreateInsert");
Object result = operationBinding.execute();
if (!operationBinding.getErrors().isEmpty()) {
return null;
DCIteratorBinding dciter =(DCIteratorBinding) bindings.get("PersonneView1Iterator");
Row row=dciter.getCurrentRow();
Statement stmt = this.getDBTransaction().createStatement(1);
try {
ResultSet rs = stmt.executeQuery("select max(cin) from personne");
while( rs.next() ){
row.setAttribute("cin", rs.getInt(1)+1);
} catch (SQLException ex) {
ex.printStackTrace();
return "go";
at run time it give an error at this line : Statement stmt = this.getDBTransaction().createStatement(1);
please check and correct me
thanks in advance

Answer 1

Hi,
Initially I would like to say that this should not be used if you are trying to get a PrimaryKey as it would cause serious concurrency issues.
For example lets say that you want whenever you create a new Employee to set his DepartmentId equal to the max department.
We could create a readOnly VO (lets name it MaxDepartmentId) with a query that returns the max departmentId:
select max(Department_Id) as maxDep from DepartmentsAfter that we need to add the MaxDepartmentId VO as a ViewAccessor in our Employees Vo,
override the create() method in the EmployeesRowImpl and add some code like this:
public class EmployeesRowImpl extends ViewRowImpl {
    @Override
    protected void create(AttributeList attributeList) {
        Row r=getMaxDepartmentId().first();
        if(r!=null){
             Number max=(Number)r.getAttribute("Maxdep");
             attributeList.setAttribute("DepartmentId", max);
        super.create(attributeList);
}That's all.
If you run this you will see that when you create a new employee it has a default value.
Gabriel.