DOCSLIB.ORG

Tomcat the Definitive Guide

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tomcat the Definitive Guide SECOND EDITION Tomcat The Definitive Guide Jason Brittain with Ian F. Darwin Beijing • Cambridge • Farnham • Köln • Paris • Sebastopol • Taipei • Tokyo Tomcat: The Definitive Guide, Second Edition by Jason Brittain with Ian F. Darwin Copyright © 2008 O’Reilly Media, Inc. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (safari.oreilly.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 or [email protected]. Editor: Simon St.Laurent Indexer: Tolman Creek Design Production Editor: Loranah Dimant Cover Designer: Karen Montgomery Copyeditor: Nancy Reinhardt Interior Designer: David Futato Proofreader: Loranah Dimant Illustrator: Jessamyn Read Printing History: June 2003: First Edition. October 2007: Second Edition. Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Tomcat: The Definitive Guide, the image of a snow leopard, and related trade dress are trademarks of O’Reilly Media, Inc. Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc., in the United States and other countries. O’Reilly Media, Inc. is independent of Sun Microsystems. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisher and authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. This book uses RepKover™, a durable and flexible lay-flat binding. ISBN-10: 0-596-10106-6 ISBN-13: 978-0596-10106-0 [M] Table of Contents Preface . ix 1. Getting Started with Tomcat . 1 Installing Tomcat 1 Starting, Stopping, and Restarting Tomcat 17 Automatic Startup 29 Testing Your Tomcat Installation 34 Where Did Tomcat Come From? 35 2. Configuring Tomcat . 38 A Word About Using the Apache Web Server 38 Relocating the Web Applications Directory 39 Changing the Port Number from 8080 42 Java VM Configuration 51 Changing the JSP Compiler 54 Managing Realms, Roles, and Users 55 Controlling Sessions 70 Accessing JNDI and JDBC Resources 75 Servlet Auto-Reloading 78 Customized User Directories 78 Tomcat Example Applications 80 Common Gateway Interface (CGI) 80 The Tomcat Admin Webapp 82 v 3. Deploying Servlet and JSP Web Applications in Tomcat . 86 Layout of a Web Application 93 Deploying an Unpacked Webapp Directory 95 Deploying a WAR File 100 Hot Deployment 106 Working with WAR Files 107 The Manager Webapp 108 Automation with Apache Ant 111 Symbolic Links 124 4. Tomcat Performance Tuning . 126 Measuring Web Server Performance 127 External Tuning 153 Internal Tuning 156 Capacity Planning 164 Additional Resources 167 5. Integration with the Apache Web Server . 169 The Pros and Cons of Integration 170 Installing Apache httpd 174 Apache Integration with Tomcat 177 Tomcat Serving HTTP over the APR Connector 194 6. Tomcat Security . 201 Securing the System 202 Multiple Server Security Models 204 Using the SecurityManager 205 Granting File Permissions 208 Setting Up a Tomcat chroot Jail 213 Filtering Bad User Input 224 Securing Tomcat with SSL 241 7. Configuration . 259 server.xml 260 web.xml 316 tomcat-users.xml 333 catalina.policy 333 catalina.properties 334 context.xml 335 vi | Table of Contents 8. Debugging and Troubleshooting . 336 Reading Logfiles 336 Hunting for Errors 337 URLs and the HTTP Conversation 337 Debugging with RequestDumperValve 342 When Tomcat Won’t Shut Down 343 9. Building Tomcat from Source . 347 Installing Apache Ant 348 Obtaining the Source 349 Downloading Support Libraries 351 Building Tomcat 352 10. Tomcat Clustering . 354 Clustering Terms 355 The Communication Sequence of an HTTP Request 356 Distributed Java Servlet Containers 366 Tomcat 6 Clustering Implementation 370 JDBC Request Distribution and Failover 388 Additional Resources 389 11. Final Words . 391 Supplemental Resources 391 Community 395 A. Installing Java . 397 B. jbchroot.c . 410 C. BadInputValve.java . 416 D. BadInputFilter.java . 426 E. RPM Package Files . 439 Index . 463 Table of Contents | vii This book is lovingly dedicated to our son Alex and our daughter Angie. —Jason Brittain Preface1 Tomcat has eased the lives of thousands of Java™ developers, supplying them with a free environment for testing anddeployingweb applications. Tomcat has provedits mettle in all kinds of environments, providing the foundation you’ll need to apply your Java expertise to the Web. What’s This Book About? Tomcat is a Java servlet container andweb server from the Apache Software Founda- tion (http://tomcat.apache.org). A web server is, of course, a program that dishes out web pages in response to requests from, for example, a user sitting at a web browser. But web servers aren’t limitedto serving up static HTML pages; they can also run programs in response to user requests andreturn the dynamicresults to the user’s browser. This is an aspect of the Web that Apache’s Tomcat is very goodat because Tomcat provides both Java servlet and JavaServer Pages (JSPs) technologies (in addi- tion to serving traditional static pages and external CGI programs written in any pro- gramming language). The result is that Tomcat is a goodchoice for use as a web server for many applications, including using it as a high performance production web server. Andit’s a very goodchoice if you want a free, open source ( http:// opensource.org) servlet andJSP engine. It can be usedstandaloneandin conjunction with other web servers such as Apache httpd. This book is about how to use Tomcat itself. If you’re looking for detailed informa- tion andtutorials about how to write web applications, be sure to read Java Servlet Programming by Jason Hunter with William Crawford (O’Reilly). ix Why an Entire Book on Tomcat? Can’t you just download and run Tomcat from the Apache Software Foundation’s web site? Well, of course you can, andyou’ll needto, but there is a lot more to Tom- cat than just getting it running. You’ll get more out of Tomcat if you understand how andwhy it was written. So in Chapter 1, Getting Started with Tomcat, we explain that. You will then be better able to make informeddecisionson choices you might needto make when installing Tomcat, so we spendthe rest of the chapter on the installation and startup procedures. In Chapter 2, Configuring Tomcat, we show you all about configuring Tomcat. We talk about when you shoulduse Tomcat as a standaloneweb server andservlet container andwhen it’s best to use Tomcat with the Apache httpd web server. Then, we show you how to configure realms, roles, users, servlet sessions, andJNDI resources, includ- ing JDBC DataSources. Next, we show how to turn on andoff the auto-reloadingof servlets, how to relocate the webapps directory, and how to map user home directories for access through Tomcat. Then, we go over how to enable anddisablethe example web applications andhow to enable common gateway interface scripting in Tomcat. And finally, we close out the chapter by introducing you to the Tomcat administration web application, which allows you to configure Tomcat through your web browser. With Tomcat installedandconfiguredjust the way you like it, you’re readyto learn more about servlet andJSP web applications andhow to deploythem into your Tomcat. In Chapter 3, Deploying Servlet and JSP Web Applications in Tomcat,we show you the layout of a web application, how to deploy a web application, and how to deploy individual servlets and JSP pages. Next, we show you how to build web application archive files and how to deploy them. To make things less tedious, we review how to automate the deployments of your web applications by copying, using the built-in manager web application, and using the Jakarta Ant build tool. Once you have Tomcat serving your web application, you may want to do some per- formance tuning. In Chapter 4, Tomcat Performance Tuning, we show you how to measure andimprove your Tomcat’s performance. We go over adjustingthe num- ber of processor Threads, JVM andOS performance issues as they relate to Tomcat, turning off DNS lookups, andhow to speedup JSPs. We roundout the chapter by discussing how capacity planning can affect performance. Tomcat works as a complete standalone web server. It supports static web pages, external CGI scripts, andmany of the other paraphernalia associatedwith a web site. However, Tomcat’s forte, its raison d’etre, is to be the best servlet andJSP engine on the block. These are the things it does best. If you already run Apache’s httpd web server anddon’twant to change everything all at once, Chapter 5, Integration with the Apache Web Server, covers the use of Tomcat with Apache httpd andtalks about the several ways of making Tomcat thrive “in front of” or “behind” an Apache httpd installation. x | Preface Whether you’re providing e-commerce, putting up a mailing list, or running a per- sonal site, when you’re connectedto the Internet, your site is exposedto a lot of peo- ple, including a few weirdos who think it’s OK to exploit the vulnerabilities in your server software for fun and/or profit. Because security is important, we devote Chapter 6, Tomcat Security, to the topic of how to keep the online thugs at bay. In Chapter 7, Configuration, we talk about the Tomcat configuration files, server.xml and web.xml, as well as tomcat-users.xml, catalina.policy, catalina.properties, and con- text.xml files.
Load more

Recommended publications
  • BOROUGH of MANHATTAN COMMUNITY COLLEGE City University of New York Department of Computer Information Systems Office S150/Phone: 212-220-1476
    BOROUGH OF MANHATTAN COMMUNITY COLLEGE City University of New York Department of Computer Information Systems Office S150/Phone: 212-220-1476 Web Programming II Class hours: 2 CIS 485 Lab hours: 2 Spring 2012 Credits: 3 Course Description: This course will introduce students to server-side web programming. Emphasis is placed on database connectivity in order to solve intermediate level application problems. Students will be tasked with web projects that facilitate understanding of tier design and programming concepts. The overall goal of this course is to create a shopping cart application with a login and database component. Prerequisites/Co-requisite: Basic Skills: ENG 088, ESL 062, ACR 094, MAT 012/051; CIS 385 Web Programming I Learning Outcomes and Assessment After completing this course, students will be able to: Outcome: Demonstrate the use of a database with server-side scripting Assessment: Lab exercises and exam questions Outcome: Demonstrate the use a Cookie and Session manager with server-side scripting Assessment: Final project, lab exercises and exam questions Outcome: Develop a database-driven website Assessment: Lab exercises Outcome: Design and develop a shopping-cart application with a login and database component Assessment: Final Project General Education Outcomes and Assessment Quantitative Skills – Students will use quantitative skills and concepts and methods of mathematics to solve problems Assessment: Use formulas and concepts of mathematics to solve problems in programming assignments Information and Technology
    [Show full text]
  • Introduction to Java
    Introduction to Java James Brucker What is Java? Java is a language for writing computer programs. it runs on almost any "computer". desktop mobile phones game box web server & web apps smart devices What Uses Java? OpenOffice & LibreOffice (like Microsoft Office) Firefox Google App Engine Android MindCraft & Greenfoot IDE: Eclipse, IntelliJ, NetBeans How Java Works: Compiling 1. You (programmer) write source code in Java. 2. A compiler (javac) checks the code and translates it into "byte code" for a "virtual machine". Java Java source Hello.java javac Hello.class byte code code compiler public class Hello { public Hello(); aload_0 public static void main( String [ ] args ) { invokespecial #1; //Method java/ System.out.println( "I LOVE programming" ); lang/Object."<init>":()V return } main(java.lang.String[]); } getstatic #2; //Field ... How Java Works: Run the Bytecode 3. Run the byte code in a Java Virtual Machine (JVM). 4. The JVM (java command) interprets the byte code and loads other code from libraries as needed. Java I LOVE programming byte Hello.class java code java virtual public Hello(); aload_0 machine invokespecial #1; //Method java/lang/Object."<init>":()V return main(java.lang.String[]); Other java classes, getstatic #2; //Field ... saved in libraries. Summary: How Java Works 1. You (programmer) write program source code in Java. 2. Java compiler checks the code and translates it into "byte code". 3. A Java virtual machine (JVM) runs the byte code. Libraries Hello, javac Hello.class java Hello.java World! Java compiler byte code JVM: Program source - load byte code execution program - verify the code - runs byte code - enforce security model How to Write Source Code? You can use any editor to write the Java source code.
    [Show full text]
  • Configuring & Using Apache Tomcat 4 a Tutorial on Installing and Using
    Configuring & Using Apache Tomcat 4 A Tutorial on Installing and Using Tomcat for Servlet and JSP Development Taken from Using-Tomcat-4 found on http://courses.coreservlets.com Following is a summary of installing and configuring Apache Tomcat 4 for use as a standalone Web server that supports servlets 2.3 and JSP 1.2. Integrating Tomcat as a plugin within the regular Apache server or a commercial Web server is more complicated (for details, see http://jakarta.apache.org/tomcat/tomcat-4.0-doc/). Integrating Tomcat with a regular Web server is valuable for a deployment scenario, but my goal here is to show how to use Tomcat as a development server on your desktop. Regardless of what deployment server you use, you'll want a standalone server on your desktop to use for development. (Note: Tomcat is sometimes referred to as Jakarta Tomcat since the Apache Java effort is known as "The Jakarta Project"). The examples here assume you are using Windows, but they can be easily adapted for Solaris, Linux, and other versions of Unix. I've gotten reports of successful use on MacOS X, but don't know the setup details. Except when I refer to specific Windows paths (e.g., C:\blah\blah), I use URL-style forward slashes for path separators (e.g., install_dir/webapps/ROOT). Adapt as necessary. The information here is adapted from More Servlets and JavaServer Pages from Sun Microsystems Press. For the book table of contents, index, source code, etc., please see http://www.moreservlets.com/. For information on servlet and JSP training courses (either at public venues or on-site at your company), please see http://courses.coreservlets.com.
    [Show full text]
  • DLCGI Advanced Uses
    DLCGI Advanced Uses Using DLCGI to achieve single sign-on with The Diver Solution In situations where authentication to DiveLine needs to be integrated with an existing authentication scheme, we provide "DLCGI", the DiveLine-Common Gateway Interface interfacing module. The "Common Gateway Interface" is a standard for interfacing external scripts and programs with a web server. How DLCGI works When dlcgi.exe is executed by the webserver, in the context of a user that the web server has already authenticated, it obtains a limited-lifetime one-time password from DiveLine. This password can be passed, via web page redirects, custom web page scripting, etc., to DivePort, NetDiver, or even ProDiver to allow the user to login. The typical strategy for using DLCGI is: 1. Configure DiveLine to accept DLCGI requests from your webserver. 2. Install dlcgi.exe in a scripts directory (e.g. /cgi-bin/) on your CGI-compliant webserver (e.g. IIS, Apache). You configure the name of your DiveLine server and other parameters using dlcgi.cfg in the same directory as the executable. 3. Restrict access to this script so that the webserver will only execute it when the user has already authenticated (e.g. Domain account). Typical uses • DivePort: Users go to the DivePort site, and are redirected to another URL for authentication. That URL, which runs dlcgi.exe, redirects the user back to the DivePort URL with a one-use authentication token. • ProDiver: When ProDiver connects to DiveLine, if configured with a DLCGI URL, it will access the URL in "raw" mode (see below) to obtain a parse-able result file containing a one-use DiveLine authentication token.
    [Show full text]
  • Solutions to Exercises
    533 Appendix Solutions to Exercises Chapters 1 through 10 close with an “Exercises” section that tests your understanding of the chapter’s material through various exercises. Solutions to these exercises are presented in this appendix. Chapter 1: Getting Started with Java 1. Java is a language and a platform. The language is partly patterned after the C and C++ languages to shorten the learning curve for C/C++ developers. The platform consists of a virtual machine and associated execution environment. 2. A virtual machine is a software-based processor that presents its own instruction set. 3. The purpose of the Java compiler is to translate source code into instructions (and associated data) that are executed by the virtual machine. 4. The answer is true: a classfile’s instructions are commonly referred to as bytecode. 5. When the virtual machine’s interpreter learns that a sequence of bytecode instructions is being executed repeatedly, it informs the virtual machine’s Just In Time (JIT) compiler to compile these instructions into native code. 6. The Java platform promotes portability by providing an abstraction over the underlying platform. As a result, the same bytecode runs unchanged on Windows-based, Linux-based, Mac OS X–based, and other platforms. 7. The Java platform promotes security by providing a secure environment in which code executes. It accomplishes this task in part by using a bytecode verifier to make sure that the classfile’s bytecode is valid. 8. The answer is false: Java SE is the platform for developing applications and applets. 533 534 APPENDIX: Solutions to Exercises 9.
    [Show full text]
  • Leukemia Medical Application with Security Features
    Journal of Software Leukemia Medical Application with Security Features Radhi Rafiee Afandi1, Waidah Ismail1*, Azlan Husin2, Rosline Hassan3 1 Faculty Science and Technology, Universiti Sains Islam Malaysia, Negeri Sembilan, Malaysia. 2 Department of Internal Medicine, School of Medicine, Universiti Sains Malaysia, Kota Bahru, Malaysia. 3 Department of Hematology, School of Medicine, Universiti Sains Malaysia, Kota Bahru, Malaysia. * Corresponding author. Tel.: +6 06 7988056; email: [email protected]. Manuscript submitted January 27, 2015; accepted April 28, 2015 doi: 10.17706/jsw.10.5.577-598 Abstract: Information on the Leukemia patients is very crucial by keep track medical history and to know the current status of the patient’s. This paper explains on development of Hematology Information System (HIS) in Hospital Universiti Sains Malaysia (HUSM). HIS is the web application, which is the enhancement of the standalone application system that used previously. The previous system lack of the implementation of security framework and triple ‘A’ elements which are authentication, authorization and accounting. Therefore, the objective of this project is to ensure the security features are implemented and the information safely kept in the server. We are using agile methodology to develop the HIS which the involvement from the user at the beginning until end of the project. The user involvement at the beginning user requirement until implemented. As stated above, HIS is web application that used JSP technology. It can only be access within the HUSM only by using the local Internet Protocol (IP). HIS ease medical doctor and nurse to manage the Leukemia patients. For the security purpose HIS provided password to login, three different user access levels and activity log that recorded from each user that entered the system Key words: Hematology information system, security feature, agile methodology.
    [Show full text]
  • Getting Started Guide with Wiz550web Getting Started Guide with Wiz550web
    2015/02/09 17:48 1/21 Getting Started Guide with WIZ550web Getting Started Guide with WIZ550web WIZ550web is an embedded Web server module based on WIZnet’s W5500 hardwired TCP/IP chip, Users can control & monitor the 16-configurable digital I/O and 4-ADC inputs on module via web pages. WIZ550web provides the firmware & web page examples for user’s customization. This page describes the following topics: ● Product Preview ● Hello world ❍ Product contents ❍ SD card initialization ❍ Data flash initialization ❍ Serial debug message ● WIZ550web Basic operations and CGI ● Basic Demo Webpage ● Examples for WIZ550web customization Users can download the following source codes from the 'WIZ550web GitHub Repository' ● Firmware source code (The projects for Eclipse IDE) ❍ Application / Boot ● Demo webpage WIZ550web GitHub Repository https://github.com/Wiznet/WIZ550web WIZ550web GitHub Page http://wiznet.github.io/WIZ550web Develop Environment - http://wizwiki.net/wiki/ Last update: 2015/02/09 products:wiz550web:wiz550webgsg_en http://wizwiki.net/wiki/doku.php?id=products:wiz550web:wiz550webgsg_en 13:05 ● Eclipse IDE for C/C++ Developers, Kepler Service Release 2 ● ARM GCC 4.8.3 (2014q1) Product Preview Hello World Product Contents Ordering Part No: WIZ550web ● WIZ550web module x 1 Ordering Part No: WIZ550web-EVB ● WIZ550web module x 1 ● WIZ550web baseboard x 1 http://wizwiki.net/wiki/ Printed on 2015/02/09 17:48 2015/02/09 17:48 3/21 Getting Started Guide with WIZ550web ● LAN cable x 1 ● Serial cable x 1 ● 12V Power adapter x 1 SD card is option for both WIZ550web and WIZ550web-EVB Refer to recommended lists of SD card. Vendor Capacity(Bytes) Type Class 2G SD n/a Sandisk 4G SDHC 4 8G SDHC 4 Samsung 4G SDHC 6 Transcend 4G SDHC 4,10 SD card Initialization WIZ550web uses Micro SD card as a storage for web content and SD card is not included as default.
    [Show full text]
  • CGI Scripts: Gateways to World-Wide Web Power
    Behavior Research Methods. Instruments. & Computers 1996,28 (2), 165-169 CGI scripts: Gateways to World-Wide Web power JAMES M. KIELEY Miyazaki International CoUege, Miyazaki, Japan The power of the hypertext-based information presentation system known as the World-Wide Web can be enhanced by scripts based on the common gateway interface (CG!) protocol. CG! scripts re­ siding on a Webserver permit the execution of computer programs that can perform a wide variety of functions that maybe useful to psychologists. Example applications are presented here, along with ref­ erence information for potential script developers. The majority ofinformation that people access via the permit users to input data by clicking on checkboxes, hypertext-based information presentation system known radio buttons, menus, reset buttons, and submit buttons, as the World-Wide Web (WWW) is actually stored in the and also by typing into text fields (Lemay, 1995). form of static files-that is, text and graphics files that COl was developed by the original programmers ofthe appear a certain way when viewed from a Web browser, UNIX-based CERN and NCSA HTTP Web servers to such as Netscape or Mosaic, because ofa command lan­ supersede a prior scripting environment called HTBIN. guage known as HTML. HTML, by its original design, is Other Web servers that support scripting, including those a simple command set used to present multimedia infor­ based on other operating systems, mayor may not use mation that can be accessed asynchronously. The capa­ the COl protocol. Early applications of COl scripts in­ bilities ofHTML, and, therefore, the WWW, can be im­ cluded using them to serve information to a browser that proved with scripts conforming to the common gateway is in a format that is otherwise unreadable, such as an SQL interface (COl) protocol.
    [Show full text]
  • The Common Gateway Interface and Server-Side Programming
    WebWeb MasterMaster 11 IFIIFI Andrea G. B. Tettamanzi Université de Nice Sophia Antipolis Département Informatique [email protected] Andrea G. B. Tettamanzi, 2019 1 Unit 3 The Common Gateway Interface and Server-side Programming Andrea G. B. Tettamanzi, 2019 2 Agenda • The Common Gateway Interface • Server-Side Programming Andrea G. B. Tettamanzi, 2019 3 Introduction • An HTTP server is often used as a gateway to a different information system (legacy or not), for example – an existing body of documents – an existing database application • The Common Gateway Interface (CGI) is an agreement between HTTP server implementors about how to integrate such gateway scripts and programs • It was typically (but not exclusively) used in conjunction with HTML forms to build database applications • Nowadays largely superseded by dynamic Web content technologies such as PHP, ASP.NET, Java Servlets, and Node.js Andrea G. B. Tettamanzi, 2019 4 The Common Gateway Interface • The Common Gateway Interface (CGI) is a de facto standard protocol for Web servers to execute an external program that generates a Web page dynamically • The external program executes like a console application running on the same machine as the Web server (the host) • Such program is known as a CGI script or simply as a CGI Andrea G. B. Tettamanzi, 2019 5 How Does That Work? • Each time a client requests the URL corresponding to a CGI program, the server will execute it in real-time – E.g.: GET http://www.example.org/cgi-bin/add?x=2&y=2 • The output of the program will go more or less directly to the client • Strictly speaking, the “input” to the program is the HTTP request • Environment variables are used to pass data about the request from the server to the program – They are accessed by the script in a system-defined manner – Missing environment variable = NULL value – Character encoding is system-defined Andrea G.
    [Show full text]
  • Common Gateway Interface Reference Guide
    COMMON GATEWAY INTERFACE REFERENCE GUIDE Copyright © 1998 The President and Fellows of Harvard College All rights reserved Common Gateway Interface (CGI) Reference Guide The Harvard Computer Society Table of Contents Introduction...............................................................................................................................................................1 How the Web Really Works ...................................................................................................................................1 GET and POST ......................................................................................................................................................1 Perl and CGI ..............................................................................................................................................................2 Here Document Quoting ........................................................................................................................................2 The CGI.pm Module...............................................................................................................................................2 Returning a Web Page...........................................................................................................................................3 Sending Mail ..........................................................................................................................................................4 Maintaining State......................................................................................................................................................5
    [Show full text]
  • Intro to Java
    Introduction to Java 1 / 10 Java I Developed for home appliances - cross-platform VM a key feature I Originally called Oak I Gained notariety with HotJava web browser that could run “programs over the internet” called applets I Gained popularity when Netscape included Java VM in Navigator web browser I JavaScript is purely a marketing label meant to capitalize on Java hype - there is no relationship between Java and JavaScript I Java is a general-purpose application programming language. I Java applets are now very rare. The bulk of Java code runs on (web) servers. 2 / 10 The Java Programming Language I Java is part of the C family. Same syntax for variable declarations, control structures I Java came at a time when C++ was king. C++ was a notoriously complex object-oriented extension to C. I Java improved on several key aspects of C++, greatly simplifying software development I Two most compelling features of Java were cross-platform deployablility (“write once, run anwhere”) and autoatic garbage collection I These two advantages, especially garbage collection, drove Java adoption 3 / 10 The Java Platform Three components of the Java platform: I The Java programming language I The Java Virtual Machine (JVM) I The Java standard library Java is both compiled and interpreted: I Java source files (ending in .java) are compiled to java bytecode files (ending in .class) I Java bytecode is then interpreted (run) by the JVM I Compiling and running can be done on different machines – bytecode is portable (more precisely, the JVM on each platform accepts the same bytecode).
    [Show full text]
  • Java Programming 24-Hour Trainer, Second Edition
    11 Introducing Java During the last two decades Java has maintained its status as one of the most popular programming languages for everything from programming games to creating mission-critical applications, such as those for trading on Wall Street or controlling Mars rovers. For the current popularity chart see the Tiobe Index at http:// www.tiobe.com/index.php/content/paperinfo/tpci/index.html. In this lesson you are intro‐ duced to some of the very basic Java terms. You also download and install the Java Development Kit (JDK) and compile your first program. WHY LEARN JAVA? The Java programming language was originally created in 1995 by James Gosling from Sun Microsystems (acquired by Oracle Corporation in 2010). The goal was to provide a simpler and platform-independent alter‐ native to C++. Java programs run inside the Java Virtual Machine (JVM), which is the same on every platform from the application programmer’s perspective. You find out what platform independence means a little later, in the section “The Life Cycle of a Java Program”. For now, let’s look at some of the reasons why Java can be your language of choice. Java is a general-purpose programming language that’s used in all industries for almost any type of application. If you master it, your chancesCOPYRIGHTED of getting employed as a software MATERIAL developer will be higher than if you specialize in some domain-specific programming languages. There are more than nine million professional Java developers in the world, and the majority of them are ready to share their knowledge by posting blogs and articles or simply answering technical questions online.
    [Show full text]