unwrap Method (SQLServerCallableStatement)

Article
11/18/2022

Returns an object that implements the specified interface to allow access to the Microsoft JDBC Driver for SQL Server-specific methods.

Syntax

  
public <T> T unwrap(Class<T> iface)

Parameters

iface

A class of type T defining an interface.

Return Value

An object that implements the specified interface.

Exceptions

SQLServerException

Remarks

The unwrap method is defined by the java.sql.Wrapper interface, which is introduced in the JDBC 4.0 Spec.

Applications might need to access extensions to the JDBC API that are specific to the Microsoft JDBC Driver for SQL Server. The unwrap method supports unwrapping to public classes that this object extends, if the classes expose vendor extensions.

SQLServerCallableStatement implements ISQLServerPreparedStatement, which is extended from the ISQLServerStatement. When this method is called, the object unwraps to the following classes: SQLServerStatement, SQLServerPreparedStatement, and SQLServerCallableStatement.

For more information, see Wrappers and Interfaces.

The following code example demonstrates how to use the isWrapperFor and unwrap methods to check the driver extensions and invoke the vendor-specific methods, such as setResponseBuffering and getResponseBuffering.

public static void executeStoredProcedure(Connection con) {  
   try {  
    CallableStatement cstmt =   
       con.prepareCall("{call dbo.stored_proc_name(?, ?)}");  
  
    // The recommended way to access the JDBC   
    // Driver-specific methods is to use the JDBC 4.0 Wrapper   
    // functionality.   
    // The following code statements demonstrates how to use the   
    // isWrapperFor and unwrap methods  
    // to access the driver-specific response buffering methods.  
  
    if (cstmt.isWrapperFor(  
      com.microsoft.sqlserver.jdbc.SQLServerCallableStatement.class)) {  
     // The CallableStatement object can unwrap to   
     // SQLServerCallableStatement.  
     SQLServerCallableStatement SQLcstmt =   
     cstmt.unwrap(  
        com.microsoft.sqlserver.jdbc.SQLServerCallableStatement.class);  
     SQLcstmt.setResponseBuffering("adaptive");  
     System.out.println("Response buffering mode has been set to " +  
         SQLcstmt.getResponseBuffering());  
     }  
  
    if (cstmt.isWrapperFor(  
      com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.class)) {  
      // The CallableStatement object can unwrap to   
      // SQLServerPreparedStatement.                    
      SQLServerPreparedStatement SQLpstmt =   
       cstmt.unwrap(  
       com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.class);  
      SQLpstmt.setResponseBuffering("adaptive");  
      System.out.println("Response buffering mode has been set to " +  
          SQLpstmt.getResponseBuffering());  
    }  
    if (cstmt.isWrapperFor(  
      com.microsoft.sqlserver.jdbc.SQLServerStatement.class)) {  
  
      // The CallableStatement object can unwrap to SQLServerStatement.   
      SQLServerStatement SQLstmt =   
        cstmt.unwrap(  
        com.microsoft.sqlserver.jdbc.SQLServerStatement.class);  
      SQLstmt.setResponseBuffering("adaptive");  
      System.out.println("Response buffering mode has been set to " +  
      SQLstmt.getResponseBuffering());  
    }  
  }  
  catch (Exception e) {  
     e.printStackTrace();  
  }  
}