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In this section, we will demonstrate how to modify the collection itself. As part of this demonstration, we will insert a member into our collection. The process of deleting a member or updating a member should involve essentially the same steps: 1. Retrieve the collection as a Java object as explained in the earlier sections. 2. Create a new member element by using an appropriate constructor of the member class. 3. Add the new member to the array. 4. Update the table with the modified collection element. Each of these steps is detailed as part of the method _demoAddingMemberToCollection() presented here: private static void _demoAddingMemberToCollection( Connection conn ) throws SQLException, ClassNotFoundException { The method _addMemberToArray() performs the first three steps, as you will see, as part of its definition. We invoke this method to obtain the modified array that contains the additional address object: AddressList modifiedCollection = _addMemberToArray(conn);

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Note It is likely that in the future the F# sequence expression syntax will include support for specifying

We then prepare and execute an update statement that updates emp_table with the new collection object: String stmtString = "update emp_table e set e.emp_address_list = "; PreparedStatement pstmt = null; try { pstmt = conn.prepareStatement( stmtString ); pstmt.setObject( 1, modifiedCollection ); pstmt.execute(); } finally { JDBCUtil.close( pstmt); } } The definition of the method _addMemberToArray() follows: private static AddressList _addMemberToArray( Connection conn ) throws SQLException, ClassNotFoundException { First, we instantiate an Address object in memory: Address newAddress = new Address( "1177 Monica Lane", null, "Cryptic St", "Los Gatos", "CA", "94877"); Next, we retrieve the collection object from the table using the techniques presented earlier: String stmtString = "select emp_address_list " + " from emp_table where empno = "; PreparedStatement pstmt = null; ResultSet rset = null; AddressList addressList = null; try { pstmt = conn.prepareStatement( stmtString ); pstmt.setInt( 1, 1 ); rset = pstmt.executeQuery(); if( rset.next() ) // assume only one row is updated { addressList = (AddressList)((oracle.jdbc.OracleResultSet) rset).getORAData(1, AddressList.getORADataFactory()); Address[] arrayInJava = addressList.getArray();

Let s build up a simple call stack to demonstrate the dynamic enlistment behavior of this infrastructure You ll use the tables shown in Figure 12-1 to mock-up an order entry scenario (The script to build this database is in XActionIEsql in the Code12 directory).

grouping and aggregation operations within the expression syntax. However, at the time of writing, it was necessary to explicitly use operators such as Seq.orderBy and Seq.groupBy for these operations.

At this point, we have an array of Address objects. We simply create a new array with space for one more element, copy the older array to it, and add the new element at the end: Address[] updatedEmpList = new Address[ arrayInJava.length + 1]; System.arraycopy( arrayInJava, 0, updatedEmpList, 0, arrayInJava.length); updatedEmpList[ arrayInJava.length ] = newAddress; for( int i=0; i < updatedEmpList.length; i++ ) { System.out.println(updatedEmpList[i].getLine1()); } We set the internal array of the AddressList object by invoking the method setArray() in it, passing our modified array as the parameter: addressList.setArray( updatedEmpList ); } } finally { JDBCUtil.close( rset); JDBCUtil.close( pstmt); } return addressList; } } // end of program

You have already seen one of the performance extensions for numeric element arrays, where you use methods such as getIntArray() to improve performance. There are two more performance extensions in the ARRAY class that you should be aware of, and these are covered in the sections that follow.

In this section you saw how you can use aggregate sequence operators and sequence expressions to query and manipulate in-memory data structures using a SQL-like syntax. This is essentially the idea behind Microsoft s LINQ technology. We apply the same techniques to queries over relational data (LINQ to SQL) later in this chapter. In 3 you saw that sequences can be used to wrap collections and that a number of collection data types implement the sequence interface. It is possible to provide parallel implementations for the iteration, aggregation, and transformation operations of these data types for instance, a parallel list implementation that uses worker threads and assume independence between the transformation steps. This idea forms the basis of PLINQ, a parallel version of LINQ. PLINQ also covers LINQ to SQL where parallelism is introduced in the SQL code that is generated behind the scenes.