The definitive guide on how to program mobile Internet agents in Java using the Aglet API. This book covers the mobile agent paradigm and how it is implemented in the Java platform. It also provides details on the entire API and covers advanced topics such as Agent design patterns and security.
From the Inside Flap
Think of the Internet as a distributed, massively parallel supercomputer that connects information repositories, databases, intelligent agents, and mobile code. Imagine sending your own personalized agents to roam the Internet. They will monitor your favorite Web sites, get you the ticket you couldnit get at the box office, or help you to remotely schedule meetings for your next overseas trip. Sound like science fiction? Maybe, but the advent of Java has truly revolutionized the Internet. It has created a global infrastructure that is just waiting for mobile agents to roam its wires and interact with millions of computers.
Who Should Read This Book? This book is about how to program mobile Internet agents in Java with the help of the Aglet application programming interface (API). A freely available implementation of the Aglet API from IBM Corporation has spurred a tremendous interest in aglets. Consequently, there have been numerous calls for a reference book on the aglet, its API, and its use. As the inventors of the aglet, we decided to put in some long nights to write the definitive book about how to program Java aglets. We hope you enjoy reading it. The book is intended for daring programmers, students, and researchers at the frontier of network programming. No particular knowledge about agent-related technologies is required, but fluency in Java is a must. .
Organization of This Book The following outline shows the progression of the material we present. Chapters 1 and 2 are a general introduction to various aspects of the mobile agent paradigm. Chapter 3 provides a bridge between the mobile agent paradigm and Java by introducing the Aglet API. Chapters 4 through 7 systematically cover the Aglet API in detail, and Chapters 8 through 10 are dedicated to advanced subjects: agent design patterns, the Aglet API and its implementation, and mobile agent security.
Chapter 1: Introduction to Mobile Agents This chapter leads you into the world of mobile agents, an emerging technology that makes it much easier to design, implement, and maintain distributed systems. We explain the benefits of mobile agents and demonstrate their impact on the design of distributed systems. The chapter also includes a brief overview of contemporary mobile agent systems.
Chapter 2: Elements of a Mobile Agent System This chapter helps you to develop a basic understanding of the elements of a mobile agent system. We present the basic conceptual model of mobile agents, which includes the two core concepts of any mobile agent system: agent and place. The chapter also describes the essentials of agent behavior, including the creation and disposal of agents and their transfer over a network.
Chapter 3: Mobile Agents with Java This chapter shows what it is that makes Java a powerful tool for agent development. This chapter introduces you to the agletoa Java-based agile agentoand gives you a brief overview of the Aglet API. The purpose of this overview is to link the mobile agent model with Java.
Chapter 4: Anatomy of an Aglet This chapter teaches you about the methods in the Aglet class that can be overridden by the programmer. These methods are systematically invoked by the system as important events in the life of an aglet. The chapter shows you the principles of using these methods, including important information about the order in which they are invoked by the system when specific events take place. With this knowledge, you will be in a position to create aglets that can perform simple tasks on remote computers.
Chapter 5: Aglet Context This chapter covers one of the key elements of the Aglet API, namely, the AgletContext interface. The interface defines the execution context for aglets, and in this chapter we teach you about the methods that an aglet can invoke in its current context to create new aglets, retrieve aglets contained in the same as well as remote contexts, and much more.
Chapter 6: Aglet Messaging This chapter covers the basics of aglet messaging. Several means of interaglet communication are supported in the Aglet API, and you will learn about simple messaging with and without reply, advanced message management, and multicast messaging between aglets. The classes covered in this chapter include Message, MessageManager, and FutureReply.
Chapter 7: Aglet Collaboration This chapter introduces the aglet proxy, AgletProxy, and describes the rationale behind this important element of the Aglet API. This overview is followed by a demonstration of different ways to control aglets to make them collaborate with one another.
Chapter 8: Agent Design Patterns This chapter focuses on a set of design patterns for creating mobile agent applications. Design patterns have proved to be highly useful in object-oriented programming and have helped developers to achieve good design of applications through reusability of validated components. We hope that the design patterns described in this chapter will serve this purpose in the context of aglet-based .
Chapter 9: Inside Aglets This chapter presents a general overview of the components of the Aglets framework, with a special focus on selected parts of the framework. After reading this chapter you should have a sufficient understanding of the inner workings of the Aglets Framework to optimize the performance of your aglets, to understand why apparently healthy aglets are malfunctioning, and overall to better use the Aglet API in your programming. .
Chapter 10: Aglet Security This chapter introduces you to network security technologies in general and mobile agent security in particular. We first show you what can go wrong when mobile agents are released in a network. This is followed by a taxonomy of attacks, which introduces you to some potential attacks related to mobile agents. We then briefly explain cryptography as a general basis of security before continuing with a description of the set of security services available for mobile agents. The remainder of this chapter is devoted to a description of security policies for mobile agent systems in general and the Aglets framework in particular. .
Appendix: The Aglet API Documentation The appendix contains the API documentation of the Aglet API (limited to the aglet package).
Bibliography We offer this list of works for further reading on related topics. The list is by no means exhaustive, and other excellent works exist on most of the .
Conventions Used in This Book All the code examples in the text have been compiled and run on Java Development Kit (JDK) 1.1.5 using the first release of IBMis Aglets Software Development Kit. Source code for examples in this book can be retrieved on-line from the Web sites listed in the Introduction.
A constant-width font is used for the following:
Code examples
public class MyFirstAglet extends Aglet {
... }
Class, method, and variable names within the text
URLs set in italics
We have attempted to be complete and accurate throughout this book. Changes in future releases of IBMis Aglets Software Development Kit, as well as changes in future releases of JavaSoftis JDK, make it impossible to be completely accurate in all cases. We welcome your feedback about this book, especially if you spot errors or omissions. We prefer to use the Aglets mailing list (see the Introduction) as the communication channel for this book. However, if you wish to contact us directly, feel free to send your electronic mail to danny@acm.
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