ADF_210：使用View Link Accessor

开发运行环境：JDeveloper 11.1.2.3.0 + Oracle Database 11g Express Edition。

实际使用中，经常需要在某个VO上增加一个Attribute，该Attribute的值来自于其它关联的的VO的Attribute值。
使用View Link有一个Accessor特性可以轻松地帮我们实现该功能。

重要步骤说明：

1. Accessor 是定义在View Link上的，默认情况下是没有定义的。
以Department和Employee为例，其一对多的关系是定义在EmpDepFkLink.xml上的。
默认情况下，Accessor是没有定义的，即Exposed in View Object没有定义。

2. 建立Accessor。

 建立Accessor后，会看到DepartmentsView1已经暴露到EmployeesView中了。

3. 在EmployeesView中增加一个Attribute：DepartmentName，Expression 表达式：DepartmentsView1.DepartmentName。


4. 运行AM
点击EmployeesView1，

查看日志，会发现两条SELECT 语句，也就是说，使用Accessor关联要调用两次SQL查询。

不过，点击前后记录，会发现不是每次都执行查询，只有新的Employee才会执行。

访问过的记录，都是从内存中获取的。

[77] INFO: No app _def_ in BindingContext for: AppModule

[78] DCUtil, returning:oracle.jbo.uicli.binding.JUApplication, for AppModule

[79] Replacing: null with: AppModule_EmployeesView1_0PageDef

[80] INFO: No app _def_ in BindingContext for: AppModule

[81] DCUtil, returning:oracle.jbo.uicli.binding.JUApplication, for AppModule

[82] INFO: No app _def_ in BindingContext for: PROJECT_GLOBAL_VARIABLES

[83] INFO: mDCRefMap lookup failed. Does the cpx have a dataControlUsages 'dc' entry? PROJECT_GLOBAL_VARIABLES

[84] Resolving VO:AppModule.EmployeesView1 for iterator binding:oracle_jbo_uicli_binding_JUIteratorBinding_9

[85] DCUtil, RETURNING: for AppModule.EmployeesView1

[86] EmployeesView1 ViewRowSetImpl.execute caused params to be "un"changed

[87] Carrying over CappedRowCount:-1for ViewRowSet:EmployeesView1

[88] Column count: 15

[89] executeQueryForCollection ViewObject:EmployeesView1, RowSet:EmployeesView1

[90] EmployeesView1>#q computed SQLStmtBufLen: 494, actual=347, storing=377

[91] SELECT Employees.EMPLOYEE_ID,         Employees.FIRST_NAME,         Employees.LAST_NAME,         Employees.EMAIL,         Employees.PHONE_NUMBER,         Employees.HIRE_DATE,         Employees.JOB_ID,         Employees.SALARY,         Employees.COMMISSION_PCT,         Employees.MANAGER_ID,         Employees.DEPARTMENT_ID FROM EMPLOYEES Employees

[92] ViewObject: [model.EmployeesView]AppModule.EmployeesView1 Created new QUERY statement

[93] Bind params for ViewObject: [model.EmployeesView]AppModule.EmployeesView1

[94] DBTransactionImpl.mDefaultSparseArrayThreshold is 20

[95] Entity with key:oracle.jbo.Key[100 ] owned by row:oracle.jbo.Key[100 ]

[96] Employees_Departments1_EmpDeptFkLink_DepartmentsView_0 ViewRowSetImpl.setParamValues params changed

[97] Employees_Departments1_EmpDeptFkLink_DepartmentsView_0 ViewRowSetImpl.execute caused params to be "un"changed

[98] Carrying over CappedRowCount:-1for ViewRowSet:Employees_Departments1_EmpDeptFkLink_DepartmentsView_0

[99] Column count: 5

[100] executeQueryForCollection ViewObject:Employees_Departments1_EmpDeptFkLink_DepartmentsView, RowSet:Employees_Departments1_EmpDeptFkLink_DepartmentsView_0

[101] Employees_Departments1_EmpDeptFkLink_DepartmentsView>#q computed SQLStmtBufLen: 250, actual=216, storing=246

[102] SELECT Departments.DEPARTMENT_ID,         Departments.DEPARTMENT_NAME,         Departments.MANAGER_ID,         Departments.LOCATION_ID FROM DEPARTMENTS Departments WHERE Departments.DEPARTMENT_ID = :Bind_DepartmentId

[103] ViewObject: [model.DepartmentsView]AppModule.Employees_Departments1_EmpDeptFkLink_DepartmentsView Created new QUERY statement

[104] Bind params for ViewObject: [model.DepartmentsView]AppModule.Employees_Departments1_EmpDeptFkLink_DepartmentsView

[105] For RowSet : Employees_Departments1_EmpDeptFkLink_DepartmentsView_0

[106] Binding param "Bind_DepartmentId": 90

[107] Entity with key:oracle.jbo.Key[90 ] owned by row:oracle.jbo.Key[90 ]

[108] RecalcExpression trueresovles to true

[109] Employees_Departments1_EmpDeptFkLink_DepartmentsView_1 ViewRowSetImpl.setParamValues params changed

[110] Employees_Departments1_EmpDeptFkLink_DepartmentsView_1 ViewRowSetImpl.execute caused params to be "un"changed

[111] executeQueryForCollection ViewObject:Employees_Departments1_EmpDeptFkLink_DepartmentsView, RowSet:Employees_Departments1_EmpDeptFkLink_DepartmentsView_1

[112] **** refreshControl() for BindingContainer :AppModule_EmployeesView1_0PageDef

[113] RecalcExpression trueresovles to true

[114] Employees_Departments1_EmpDeptFkLink_DepartmentsView_2 ViewRowSetImpl.setParamValues params changed

[115] Employees_Departments1_EmpDeptFkLink_DepartmentsView_2 ViewRowSetImpl.execute caused params to be "un"changed

[116] executeQueryForCollection ViewObject:Employees_Departments1_EmpDeptFkLink_DepartmentsView, RowSet:Employees_Departments1_EmpDeptFkLink_DepartmentsView_2

[117] RecalcExpression trueresovles to true

[118] Employees_Departments1_EmpDeptFkLink_DepartmentsView_3 ViewRowSetImpl.setParamValues params changed

[119] Employees_Departments1_EmpDeptFkLink_DepartmentsView_3 ViewRowSetImpl.execute caused params to be "un"changed

[120] executeQueryForCollection ViewObject:Employees_Departments1_EmpDeptFkLink_DepartmentsView, RowSet:Employees_Departments1_EmpDeptFkLink_DepartmentsView_3

[121] ##### QueryCollection.finl oracle.jbo.Key[90 ]

Project 下载：ADF_ViewLink_Accessor.7z

参考文献：
1. http://andrejusb.blogspot.jp/2011/12/groovy-with-view-link-accessor.html