Table of Contents
Advertisement
DEVELOPING COLDFUSION 9 APPLICATIONS
Using Web Elements and External Objects
Passing data by reference and value
The proxy generators let you specify whether to pass parameters and return values by reference or by value.
About passing by reference and value
When you pass data by reference, the information transferred between the Java Proxy and the .NET side is a logical
pointer to the underlying .NET object, which continues to reside on the .NET side. When you pass data by value, the
transferred information contains a copy of the contents of the .NET object, which could or continue to reside on the
.NET side after a function call. Passing by reference and value have different advantages.
When you pass data by reference, only changed values are passed between the Java proxy and the .NET object directly.
All other information is passed as reference to its representation in the corresponding objects. Because the reference
is typically much smaller than the actual object, passing by reference is typically fast. Also, because the reference points
to a .NET object that continues to exist on the .NET side, if that .NET object is updated, the updates are immediately
accessible to the proxy object on the Java side. The disadvantage of reference proxies is that any access to data in the
underlying object (for example, field or method accesses) requires a round trip from the Java side to the .NET side
(where the information resides) and back to the Java side.
When you pass data by value, a copy of the data is passed between .NET and Java. Because the data object itself is
typically bigger than a reference, passing an object by value takes longer than passing it by reference. Also, the value
that is passed is a snapshot of the object taken at the time that it was passed. The passed object maintains no connection
to the underlying .NET object, therefore, the passed value does not reflect any updates to the underlying .NET object
that are made after the object is passed. The advantage of passing data by value proxies is that all data in the object is
local to the Java side, and field accesses are fast, because they do not require a round trip to the .NET side and back to
get the data.
The choice of whether to use reference or value proxies depends on the desired semantics of the generated proxies, and
on performance.
• In general, use reference proxies (the default), because they maintain the normal parameter-passing semantics of
Java and C#.
• In general, use value proxies in any of the following cases:
• The class functions always must pass parameter values and return values back and forth.
• The class object contains little data.
• The object data changes frequently, and the object is either relatively small or the frequency of accesses to data
outweighs the time taken to transfer the object.
Specifying the data passing method
When you use the JNBProxy.gui tool to generate proxies, you can designate the proxies that pass by reference and
which proxies pass by value. The default proxy type is reference.
To set the data passing method for a class, right-click on the class in the Exposed Proxies pane. Select the desired
passing method from the list that appears. After you select the passing method, the color of the proxy class changes, to
indicate its type: black for reference, or blue for value (public fields/properties style).
Set the passing method for multiple proxy classes simultaneously
Select Project > Pass By Reference / Value from the menu bar.
1
2
The Pass by Reference / Value dialog box lists all proxy classes in the Exposed Proxies pane. Select the classes whose
passing value you want to set.
3
Click the Reference or Value (Public fields/properties) button to associate the selected classes to the desired type.
Last updated 8/5/2010
1169
Advertisement
Table of Contents
