Questions and Answers about using JRE and JDK with ArcIMS 4.0.1 for Windows
General JRE and JDK Questions

Q: What is JRE?
A: Java Runtime Environment. JRE provides the core classes and files necessary for you to execute Java applications. The Java applications are made up of one or more Java ARchive (JAR) files or .class files. You cannot develop and compile Java applications using the runtime environment. ArcIMS Java applications requiring JRE include Author, Designer, and Administrator as well as ArcIMS Manager, Remote Manager, and the ArcIMS Java Viewers.

Q: What is JDK?
A: Java Development Kit, also called Java 2 Software Development Kit (SDK). JDK provides a development environment for Java applications. With JDK, you can compile Java class (.java) files to create JAR and .class files and can compile pages developed using JSP.

Q: What is J2SE?
A: J2SE is the specification for the Java Platform, Standard Edition. It consists of a standard API. JRE and Java 2 SDK (JDK) are used to implement the specification.

Q: What's the difference between a system and private JRE?
A: The system JRE is the active version in the registry. Private JREs are not registered and are only available to the application that copied the files to disk.

ArcIMS 4.0.1 Specific JRE and JDK Questions

Q: Which version of JRE does ArcIMS 4.0.1 use?
A: For a list of supported JRE versions please see the ArcIMS 4.0.1 System Requirments page.

Q: Are there any ArcIMS applications that require JDK instead of JRE?
A: Yes. If you plan to use JSP with the Java Connector, your servlet engine must be JDK-enabled. ArcIMS components using the Java Connector are the ArcIMS Service Administrator, Metadata Explorer, and your own JSP applications. This version of JDK does not need to be the same version of the JRE used with ArcIMS. Note: When installing JDK, you are given the option to install a system JRE. If you do install a greater version of JRE than is currently on your system, you should run through the ArcIMS Post-install, selecting Custom- ArcIMS JRE Configuration for Manager, to ensure that ArcIMS will continue to work properly.

Q: What version of JRE is installed with ArcIMS?
A: The ArcIMS install will copy the JRE 1.4.0 files under <ArcIMS installation directory>\jre\j2re1.4.0. This is a 'private' JRE for use with our stand alone apps ( Administrator, Author, Designer)-- it will not be used by any other app that uses a JRE. In addition, during the Post-install users will be prompted to install JRE 1.4.0 if the install does not detect a system JRE version 1.3.1_02 or greater.

Q: On the ArcIMS JRE Configuration for Manager panel, what does the "Use the system JRE for Author, Designer, and Administrator" check box mean?
A: It means you want the stand alone applications (Administrator, Author, and Designer) to use the system JRE instead of the 'private' jre located under the <ArcIMS installation directory>\jre\j2re1.4.0 directory . In other words, both manager and the stand alone applications will use the same JRE.

Q: Can I have multiple versions of JRE on my machine?
A: Yes, but we strongly advise that you stick with one JRE due to a known compatibility issue between the JRE 1.4 plug-in and JRE 1.3.
In theory, you SHOULD be able to have multiple JREs and SHOULD be able to switch between them in the Java plug-in panel. However, you CANNOT do this if version 1.3.x and 1.4.x are on the same machine. There is a known bug in the Java 1.4 plug-in that prevents this from working. So if you have these two versions on your machine, the last one installed wins. If you do not remember which one was the last JRE installed, you can determine the winning JRE by running through our Post- install and selecting Custom-Configure System JRE. Whichever JRE appears in the Browse To box on the 'ArcIMS JRE Configuration for Manager' panel is the winner. Behind the scenes, this panel is looking in the registry at the HKEY_CLASSES_ROOT\Jarfile\shell\open\command. The jar files must be in this JRE's lib\ext.

Q: What version of JRE is installed with the Viewer Download?
A: On a machine that does not contain JRE, installing the viewer download will prompt the user to install JRE 1.3.1_02 (Internet Explorer) or send the user to Sun's web site to download the latest JRE (Netscape).

Q: Why does ArcIMS install one version of JRE for ArcIMS and another for the Viewer Download?
A: We've made some changes to ArcIMS stand alone applications and Manager that are specific to JRE 1.4.0. Installing JRE 1.4 with the ArcIMS install allows us to stay current and to take advantage of new features. The ArcIMS Java Viewers will work with both JRE 1.3.1_02 and 1.4.0. We chose to install JRE 1.3.1_02 with the Viewer download because of a problem launching JRE 1.4.0 during the Viewer installation. If you have JRE 1.4.0 as your system JRE, the Viewer download will accept this as a valid JRE and copy the necessary JAR files to that location.

Q: Can I use the JRE directory located under my JDK directory?
A: No, this is not a system JRE. For example: Install JDK 1.3.1_02, under the c:\jdk1.3.1_02 directory is a JRE directory. This is not the system JRE directory. The system JRE directory is located under c:\program files\javasoft\jre\1.3.1_02.

Q: Why do the ArcIMS Java applications no longer work when I change to a different system JRE?
A: When ArcIMS is installed, some ArcIMS JAR files are placed in the current system JRE. When you change to another JRE, these JAR files are not part of the system JRE, and ArcIMS cannot locate them. If this should happen, run through the ArcIMS Post-install, selecting Custom- ArcIMS JRE Configuration for Manager. This will ensure that ArcIMS is using the correct JRE.