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WrapperJarApp Integration (Windows)

Method 4 - WrapperJarApp Integration (Windows)

Overview

The fourth and final method is to use the WrapperJarApp helper class to launch the application. This is another simple way to integrate with the Wrapper when the application is already configured to run as an executable jar.

There are some things to be aware of when using this method however. When the Wrapper shuts down the JVM, there is no direct call to an application requesting that it shutdown cleanly. Rather, the Wrapper will exit the JVM by calling System.exit() from within the JVM. If the application has registered its own Shutdown Hook, it will be invoked, giving the application a chance to shutdown cleanly. If on the other hand, a Shutdown Hook is not registered, then the application will suddenly exit like pressing CTRL-C in the console (command window). Both cases, with and without a Shutdown Hook, provide the exact same behavior as if the application was running without the Wrapper.

When integrating with this Method 4 (WrapperJarApp helper class), the WrapperJarApp class replaces an application's main class. This gives the WrapperJarApp class a chance to immediately initialize the WrapperManager and register the JVM with the Wrapper. The WrapperJarApp class then manages all interaction with the Wrapper as well as the life-cycle of an application. When the Wrapper sends a start message to the JVM via the WrapperManager, the jar's manifest is inspected and its configured main class is called. The WrapperJarApp creates a new ClassLoader which is able to load classes from the executable jar file as well as any other jar files referenced within its manifest file.

The WrapperJarApp helper class is told how to launch the application by passing the absolute or relative location of the executable jar file, followed by any additional application parameters to the main method of the WrapperJarApp.

Detailed Instructions

This section will walk you through a detailed explanation of how to configure Hudson, an integration engine, to run within the Wrapper. Most other applications deployed as executable jars can be integrated by following the same steps.

Install Hudson

This tutorial will start with a clean install of Hudson. We used "Hudson version 1.285" so the exact steps may be slightly different depending on the exact version installed. Hudson is deployed as a file called hudson.war. This is to enable it to be deployed as a web application, but it is also an executable jar. We will install Hudson in a directory, D:\Hudson. Create bin, lib, conf, and logs directories and place the hudson.war file inside the lib directory.

Installing Wrapper Files

There are four directories which are required to be configured in order to be able to use the Wrapper.

bin directory

First, please copy the following files into the Hudson bin directory:

{WRAPPER_HOME}\bin\wrapper.exe
{WRAPPER_HOME}\src\bin\App.bat.in
{WRAPPER_HOME}\src\bin\InstallApp-NT.bat.in
{WRAPPER_HOME}\src\bin\UninstallApp-NT.bat.in

Rename the three batch files with reflecting your application name as follows. Be sure to remove the .in extensions so that the files all end in .bat.

(Depending on how your file explorer is configured on your computer, you may not be able to see file extensions.)

You should now have:

{HUDSON_HOME}\bin\Hudson.bat
{HUDSON_HOME}\bin\InstallHudson-NT.bat
{HUDSON_HOME}\bin\UninstallHudson-NT.bat

The wrapper.exe file is the actual Wrapper executable. The three batch files are used to run Hudson in a console, and to install and uninstall it as a Windows Service.

These batch files should not require any modification. They do assume that the wrapper.conf file will be located within a conf directory (one level up, ../conf/wrapper.conf). If you wish to place the wrapper.conf file somewhere else, then the three batch files will require appropriate modification.

lib directory

Copy the following two files into the Hudson lib directory:

{WRAPPER_HOME}\lib\wrapper.dll
{WRAPPER_HOME}\lib\wrapper.jar

The wrapper.dll file is a native library file required by the portion of the Wrapper which runs within the JVM. The wrapper.jar file contains all of the Wrapper classes.

conf directory

The Wrapper requires a configuration file "wrapper.conf" for each application. The standard location for this file is in a conf directory in the application's home directory. Please copy the following template file wrapper.conf.in into the conf directory of Hudson.

{WRAPPER_HOME}\src\conf\wrapper.conf.in

Rename the file as follows. Be sure to remove the .in extension so that the file is named wrapper.conf.

You should now have:

{HUDSON_HOME}\conf\wrapper.conf

If you wish to relocate the configuration file wrapper.conf, you are free to do so. You will need to modify the batch files copied into the bin directory above, to reflect the new location.

logs directory

The default configuration file wrapper.conf will place a wrapper.log file in a logs directory under the application's home directory.

{HUDSON_HOME}/logs

If you wish to place the wrapper.log file in another location, you will need to edit the wrapper.conf file and modify the wrapper.logfile property to reflect the new location.

The Java Command Line

In the case of an executable jar, the Java command line is quite simple. In the case of Hudson, you would simply go to the Hudson directory and execute:

java -jar C:\Hudson\lib\hudson.war

Any arguments would be passed in as follows:

java -jar C:\Hudson\lib\hudson.war arg1 arg2 arg3

Modifying the "wrapper.conf" File

In order to be able to use the above Java command line with the Wrapper, we need to break up the command line's components into a configuration file. Open the wrapper.conf file into an editor and make the changes below.

NOTE

Where properties are mentioned below, links are provided to their descriptions. Please take the time to review the descriptions of any properties which are modified. In many cases, there are further details on their usage which are not mentioned here.

Java Executable

First is to extract the Java executable and assign the location path to the wrapper.java.command property:

wrapper.java.command=java

Classpath

Next, comes the classpath, which is configured using the wrapper.java.classpath.<n> properties. Java does not actually allow you to specifiy a classpath when running with the -jar parameter. But this integration with the Wrapper works a little differently. The Wrapper requires that its wrapper.jar be specified in the classpath:

wrapper.java.classpath.1=C:\Hudson\lib\wrapper.jar

Main Class

When using the Wrapper and the WrapperJarApp helper class, Java is not executing the jar directly. It is necessary to specify the helper class as the main class of the application. The main class executed by Java when launched is specified by using the wrapper.java.mainclass property as follows:

wrapper.java.mainclass=org.tanukisoftware.wrapper.WrapperJarApp

Application Parameters

Application parameters are set using the wrapper.app-parameter.<n> properties. In this case, the command line to launch Hudson does not specifiy any application parameters, but it is necessary to tell the WrapperJarApp helper class which jar to execute. This is done as follows:

wrapper.app.parameter.1=C:\Hudson\lib\hudson.war

Library Path

In order to use the Wrapper, there is one more property which much be set. The Wrapper makes use of a native library to control interactions with the system. This library file wrapper.dll needs to be specified on the library path supplied to the JVM.

Hudson does not have any native libraries of its own, but if it did, the directories where they were located would also need to be specified. The library path is set using the wrapper.java-library-path.<n> properties.

wrapper.java.library.path.1=C:\Hudson\lib

Putting It All Together

Putting it all together, we get the following:

wrapper.java.command=java

wrapper.java.classpath.1=C:\Hudson\lib\wrapper.jar

wrapper.java.library.path.1=C:\Hudson\lib

wrapper.java.mainclass=org.tanukisoftware.wrapper.WrapperJarApp

wrapper.app.parameter.1=C:\Hudson\lib\hudson.war

Notice, while these configurations will work correctly on this particular machine, it is highly dependent on the directory structure and platform. By taking advantage of the fact that the Wrapper always sets the working directory to the location of the wrapper.exe file and by making use of a single environment variable, we are able to modify the above properties so that they are completely platform and machine independent:

wrapper.java.command=%JAVA_HOME%/bin/java

wrapper.java.classpath.1=../lib/wrapper.jar

wrapper.java.library.path.1=../lib

wrapper.java.mainclass=org.tanukisoftware.wrapper.WrapperJarApp

wrapper.app.parameter.1=../lib/hudson.war

Windows Service Properties

(See:Windows Versions supported by Wrapper)

The final step is to set the Windows Service Properties properties. We will just set the properties which should be changed. But there are several others available. See the documentation for details on their usage. Suggested values for these variables are shown below.

wrapper.ntservice.name=Hudson
wrapper.ntservice.displayname=Hudson Integration Engine
wrapper.ntservice.description=Hudson Integration Engine

INFO

The properties are set in the wrapper.conf file found in the conf folder from the Wrapper installation.

Trying It Out

Hudson can now be run by simply executing the batch file bin\Hudson.bat. Because of the way the Wrapper sets its current directory, it is not necessary to run this batch file from within the bin directory. Please try running the application once as a console application to verify the configuration before attempting to run it as a service.

The first time Hudson starts up, it will create its configuration files within the current user's home directory. Note that this will most likely be a different location when running as a service versus when running in a console window.

Congratulations. Your application should now be up and running.

If you did have any problems, please take a look at the Troubleshooting section for help with tracking down the problem.