B4J Question ResultSet MetaData Oracle

XbNnX_507 · Apr 30, 2019

Hi, i'm getting an extrange error here.

B4X:

    CallableStatement.RunMethod("registerOutParameter", Array( CursorIndex, OracleTypes.GetField("CURSOR")) )
    CallableStatement.RunMethod("execute", Null) 
    Dim rs As ResultSet = CallableStatement.RunMethod("getCursor", Array(CursorIndex)) '
    Dim jrs As JavaObject = rs
    Dim rsmd As JavaObject = jrs.RunMethod("getMetaData", Null)   ' <- error here

B4X:

Waiting for debugger to connect...
Program started.
Error occurred on line: 61 (Main)
java.lang.RuntimeException: Method: getMetaData not found in: oracle.jdbc.driver.ForwardOnlyResultSet
    at anywheresoftware.b4j.object.JavaObject$MethodCache.getMethod(JavaObject.java:363)
    at anywheresoftware.b4j.object.JavaObject.RunMethod(JavaObject.java:120)
    at b4j.example.main._procedurequery(main.java:194)
    at b4j.example.main._appstart(main.java:111)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:632)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:237)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:167)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:91)
    at anywheresoftware.b4a.shell.ShellBA.raiseEvent2(ShellBA.java:98)
    at anywheresoftware.b4a.BA.raiseEvent(BA.java:78)
    at b4j.example.main.start(main.java:38)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$166(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$179(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$177(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$178(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)

Isn't this method supposed to return the resulset metadata?

DonManfred · Apr 30, 2019

XbNnX_507 said:
Isn't this method supposed to return the resulset metadata?

the cursor does not have such a method based on the error.

XbNnX_507 said:
getMetaData not found in: oracle.jdbc.driver.ForwardOnlyResultSet

XbNnX_507 · Apr 30, 2019

DonManfred said:
the cursor does not have such a method based on the error.

what about the java resultset ?

B4X:

 Dim rs As ResultSet = CallableStatement.RunMethod("getCursor", Array(CursorIndex)) ' <- this is doing the casting

DonManfred · Apr 30, 2019

no idea. Check the documentation. i never worked with stored procedures.
I just interpreted the Error

XbNnX_507 · Apr 30, 2019

Ok thanks. @DonManfred .

Maybe someone else have other idea?

Erel · Apr 30, 2019

Are you using B4J v7.3?

XbNnX_507 · Apr 30, 2019

Erel said:
Are you using B4J v7.3?

Yes. Java JDK 1.8.211

OliverA · May 1, 2019

It may not be possible. According to the answer to a question posted here: https://community.oracle.com/thread/196300 https://community.oracle.com/thread/196300, the cursor returned by your stored procedure is a oracle.jdbc.driver.ForwardOnlyResultSet and that object seems to be limited on the methods that are available (a limited subset of a "regular" result set object).

Erel · May 1, 2019

getMetaData is part of ResultSet interface. It should be there. It might be a different issue related to the way the driver is implemented. Worth try to access this method with jReflector.

OliverA · May 1, 2019

Looks like the standard prepareCall method that the SQL library is using will only return a ForwardOnlyResultSet. That object's interface is limited (other methods do not work, but with a different error messsage). There is another prepareCall method whose signature is

CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency)

Where resultSetType can be

ResultSet.TYPE_FORWARD_ONLY
ResultSet.TYPE_SCROLL_INSENSITIVE
or ResultSet.TYPE_SCROLL_SENSITIVE

and sesultSetConcurrency can be

ResultSet.CONCUR_READ_ONLY
or ResultSet.CONCUR_UPDATABLE

For the standard prepareCall, the resultSetType is ResultSet.TYPE_FORWARD_ONLY and resultSetConcurrency is ResultSet.CONCUR_READ_ONLY. You'll need to do your own prepareCall with resultSetType set to either ResultSet.TYPE_SCROLL_INSENSITIVE or ResultSet.TYPE_SCROLL_SENSITIVE. In order to do you own call, you'll need to get a hold of the connection object of the SQL object.

Edit: Forgot sources and looks like there are some limitations that you may run into when using the prepareCall mentioned above.
Sources:
Limitations of ForwardOnlyResultSet:
https://www.javamadesoeasy.com/2015/12/solve-javasqlsqlexception-invalid.html
https://coderanch.com/t/487347/databases/Invalid-operation-resultset-beforeFirst
Info on prepareCall:
https://docs.oracle.com/cd/A97335_02/apps.102/a83724/resltse2.htm
Please read "Result Set Limitations and Downgrade Rules" section!

XbNnX_507 · May 1, 2019

Well after trying everything with my little to non existent java knowledge
( that's why i use b4j lol )...
i did this...

B4X:

Dim JO As JavaObject = Me
Dim rsmd As JavaObject =    JO.RunMethod("getMeta", Array ( rs ) ) '
#if java
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.ResultSetMetaData;
 
 public ResultSetMetaData  getMeta(ResultSet rs) throws SQLException {
    ResultSetMetaData rsmd = rs.getMetaData();
    return rsmd;
  }
#End If

From there i can do

B4X:

rsmd.RunMethod("getColumnType", Array(index))

and it works.

Erel said:
Worth try to access this method with jReflector.

could be easier with jReflector but me and java not so well...

OliverA said:
For the standard prepareCall, the resultSetType is ResultSet.TYPE_FORWARD_ONLY and resultSetConcurrency is ResultSet.CONCUR_READ_ONLY.

Possibly not related to the resulset type itself but the metadata type ( oracle ).

thanks @OliverA , @Erel

OliverA · May 1, 2019

XbNnX_507 said:
and it works.

XbNnX_507 said:
public ResultSetMetaData getMeta(ResultSet rs) throws SQLException {

Looks like it was just a casting issue. By calling your inline java method, you're recasting rs as a ResultSet object, which allowed you to call the getMetaData method. Good catch!

B4J Question ResultSet MetaData Oracle

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