ADF_101：如何在一个事务中插入一对多关系的多个EO对象?

开发环境：JDeveloper 11.1.2.2.0 + Oracle XE Database 10gR2。

考虑这种情况：数据库中Departments表和Employees表是一对多的关系，在Employee表中有DepartmentId字段，并且作为外键约束。
也就是说，插入一个Employee对象时，必须要先知道DepartmentId。
如果Department对象不存在，那么就先要插入Department对象，得到DepartmentId后，再插入Employee对象。
使用ADF-BC如何调整这两次插入操作先后顺序呢？如何保证两次插入操作在一个事务之中呢？

首先假定Departments表和Employees表的主键都是通过Sequence获取的。
如何在程序中获取Sequence的下一个值，请参考《ADF-BC中EO常用操作代码之三：增加EO（1）》

重要步骤说明：

1. 在AM中增加方法：

    public void newEmployeeForNewDepartment(String firstName, String departmentName) {
        Date date = new Date(Date.getCurrentDate());
        Timestamp today = new Timestamp(date);

        // 1. Create a new employee
        EmployeesImpl newEmployee = createNewEmployee();
        // 2. Create a new department
        DepartmentsImpl newDepartment = createNewDepartment();
        newDepartment.setDepartmentName(departmentName);
        // 3. Set the department id to which the employee pertains        
        newEmployee.setDepartmentId(newDepartment.getDepartmentId());
        newEmployee.setFirstName(firstName);
        newEmployee.setLastName("Test");
        newEmployee.setEmail(today.toString());
        newEmployee.setHireDate(today);
        newEmployee.setJobId("AD_VP");
     
        // 4. Commit the transaction
        getDBTransaction().commit();
        // 5. Construct a bean to hold new supplier id and product id

        System.out.println(newEmployee.getEmployeeId());
        System.out.println(newDepartment.getDepartmentId());       
    }

    private EmployeesImpl createNewEmployee() {
        EntityDefImpl productDef = EmployeesImpl.getDefinitionObject();
        return (EmployeesImpl)productDef.createInstance2(getDBTransaction(), null);
    }

    private DepartmentsImpl createNewDepartment() {
        EntityDefImpl supplierDef = DepartmentsImpl.getDefinitionObject();
        return (DepartmentsImpl)supplierDef.createInstance2(getDBTransaction(), null);
    }

2. 定制Employees EO（即一对多关系中“多”的一方），重写方法：postChanges

    public void postChanges(TransactionEvent e) {
        // If current entity is new or modified
        if (getPostState() == STATUS_NEW || getPostState() == STATUS_MODIFIED) {
            // Get the associated department for the employee
            DepartmentsImpl deptEO = (DepartmentsImpl)getDepartments1();
            // If there is an associated department
            if (deptEO != null) {
                // And if it's post-status is NEW
                if (deptEO.getPostState() == STATUS_NEW) {
                    // Post the department before posting this entity
                    deptEO.postChanges(e);
                }
            }
        }
        super.postChanges(e);
    }

说明：重写后的逻辑保证当插入或修改Employees EO时，首先插入与其关联的Department EO。
也就是说，虽然在newEmployeeForNewDepartment方法中先插入的是Employee，但实际上经过重postChanges后，先插入的是Department（即一对多关系中“一”的一方）。
这样就可以保证在插入Employee时，可以得到其关联的DepartmentId。

3. 运行AM测试


Project 下载：ADF_BC_EO_MasterDetail.7z

参考文献：
1. 《Fusion Developer's Guide for ADF》 之 Controlling Entity Posting Order to Avoid Constraint Violations