Gene Callahan

We set out to build a generic framework for creating Java client/server relationships. Our hope was to encapsulate all of the messy details of the relationship, allowing developers writing a client or a server to focus just on their particular application. This would allow our team to swiftly create client/server relationships relying on robust, fully debugged classes to handle communications. We wanted a framework that was simple and easy to use, but flexible enough to handle multiple communications methods. Motivation It has generally been difficult to set up the communications for a new client/ server architecture. The first hurdle is to decide which of various methods to use: custom-parsed data on a socket, serialization, Remote Method Invocation (RMI), JavaSpaces, a proprietary middleware package, and so forth. The next issue to be tackled is connection managemen... (more)

PropArgs - Every Programmer's Dream

A common set of programming problems drove us to develop a Java class we call PropArgs. Consider the following questions a programmer may want answered about a program: Which RDBMS instance should data come from? Does this particular user have any personal preferences I should be setting? Should debugging code be executed during a particular run of a program? Are there different execution paths based on the current operating system? Should the programmer be operating in batch or interactive mode? What directory should disk output be written to? The common factor in these questio... (more)

Secrets of Java Serialization

Serialization in Java is an operation in which an object's internal state is translated into a stream of bytes. This binary stream or image of the object is created in an operating system-neutral network byte order. The image can be written to a disk, stored in memory, or sent over a network to a different operating system. This amazing feat requires little or no work on the part of the programmer. Just implement the serializable interface, which contains no methods, and call the writeObject() method on your object, and it's serialized! You can serialize an object to or from any ... (more)

Clarify Your Code in the Functional Style

In creating the HotScheme interpreter (JDJ Vol. 4, Issue 1), we decided to employ functional programming concepts to Java, our implementation language, whenever it was practical. Functional programming has a number of advantages over more traditional procedural code, which we will enumerate below. The common thread uniting these advantages is an attempt to create code that's conceptually transparent. Employing this functional style directly in Java allowed us to define many Scheme functions in Java the same as they'd be written in Scheme itself. We wouldn't recommend attempting t... (more)

Design Parameters in a Java Interpreter

This article describes our use of design patterns to create an interpreter in Java, and shows how it can be built in a "pure," object-oriented fashion. .The patterns we use are from Design Patterns: Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson and Vlissides, published by Addison Wesley in 1995. (We'll refer to this book henceforth as DP.) What Did We Build? HotScheme is an online, multiplatform interpreter of the Lisp dialect Scheme, with GUI front-end and interactive Internet capabilities. It's currently implemented as a Java applet, although the core of t... (more)