The Java Service Wrapper has the ability to print the Java version specified with the wrapper.java.command, and to prevent the application from starting if the version of Java is not within a configured range.

• wrapper.java.version.output
• wrapper.java.version.timeout
• wrapper.java.version.fallback
• wrapper.java.version.min
• wrapper.java.version.max

Compatibility :	3.5.17
Editions :
Platforms :

It can sometimes lead to unexpected or surprising behaviors when running a Java application with a different Java version than intended for the program.

Therefore it might be helpful to see the exact version of the JVM, which is being used before the application is being started.

The Wrapper will print out the exact version of the JVM if the wrapper.java.version.output property is set to TRUE.

As of version 3.5.55, the default value is based on the value of wrapper.java.query.loglevel:
 - If wrapper.java.query.loglevel is set to DEBUG, wrapper.java.version.output defaults to FALSE.
 - If wrapper.java.query.loglevel is set to INFO or any higher level, wrapper.java.version.output defaults to TRUE.

Prior to version 3.5.55, the default value was "FALSE".

The Wrapper will also automatically output the JVM version, if it runs in debug mode.

wrapper  | Launching a JVM...
jvm 1    | java version "1.6.0_24"
jvm 1    | OpenJDK Runtime Environment (IcedTea6 1.11.5) (6b24-1.11.5-0ubuntu1~10.04.2)
jvm 1    | OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)
jvm 1    | WrapperManager: Initializing...

Compatibility :	3.5.27
Editions :
Platforms :

Number of seconds that the Wrapper will wait for the Java version to be printed. If this timeout exceeds, the Wrapper will kill the child process and resolve the Java version to the minimum supported value.

For most users, this timeout will never be reached because printing the JVM version is fast. However, it may happen on slow machines that the JVM is taking a lot of time to start. If the delay reaches the timeout, then the child process is killed and the JVM version will not be printed.

The default value is 30 seconds. If you set the value to 0, then the Wrapper will wait indefinitely for the child process to terminate.

wrapper  | Launching a JVM...
wrapper  | Child process: Java version: timed out
jvm 1    | WrapperManager: Initializing...

Compatibility :	3.5.38
Editions :
Platforms :

This property is used in case the Wrapper fails to parse the output of 'java -version'.

If it is not set, the Java version will be resolved to the lowest supported version, but the Wrapper will stop when the following properties are used:

• wrapper.java.version.min
• wrapper.java.version.max
• wrapper.java.additional.<n>.java_version.min
• wrapper.java.additional.<n>.java_version.max

When wrapper.java.version.fallback is used however, all the above properties can be used even if the 'java -version' output would fail to be parsed.

wrapper.java.version.fallback=1.8

Compatibility :	3.5.35
Editions :
Platforms :

Specifies the minimum version of Java for which the Wrapper is allowed to launch the Java Application.

The default value is '1.4' which is the oldest JVM version supported by the Wrapper. Any lower value is invalid and will cause the Wrapper to stop.

The value can be in the format '1.major[.minor[_revision]]' or 'major[.minor[.revision]]', regardless the version of Java. This is done to support both numbering schemes returned by 'java -version': prior to Java 9 the first format was used, while Java 9 and above use the second format.

The brackets indicate that the minor and revision components are optional. Leaving one or both unspecified means that these placeholders will accept any number.

wrapper.java.version.min=1.7

wrapper.java.version.min=8.0.40

Compatibility :	3.5.35
Editions :
Platforms :

Specifies the maximum version of Java for which the Wrapper is allowed to launch the Java Application.

The default value is 'UNLIMITED' which allows the Wrapper to start the Java application with the latest versions of Java. Usually this is expected to work thanks to backward compatibility ensured through the versions of Java. However, the practice is sometimes different, and it is advised to use a version of the Wrapper released after (or close to) the release date of Java, as the compatibility can be tested and confirmed.

The value can be in the format '1.major[.minor[_revision]]' or 'major[.minor[.revision]]', regardless the version of Java. This is done to support both numbering schemes returned by 'java -version': prior to Java 9 the first format was used, while Java 9 and above use the second format.

The brackets indicate that the minor and revision components are optional. Leaving one or both unspecified means that these placeholders will accept any number.

wrapper.java.version.max=9.0.1

wrapper.java.version.max=9

• wrapper.java.command (1.0.0)

  Sets the path to the Java executable.

• wrapper.java.command.resolve (1.0.0)

  Specifies whether the Wrapper should try to resolve the specified Java command or continue using the unresolved path as possibly defined.

• wrapper.java.command.loglevel (3.1.2)

  Controls at which log level the generated command line will be logged.

• wrapper.java.detect_debug_jvm (3.3.6)

  Enables the detection of a debugger in the command line.

• wrapper.java.version.fallback (3.5.38)

  Specifies a fallback value to be used when the Java version failed to be parsed.

• wrapper.java.version.max (3.5.35)

  Specifies the maximum version of Java for which the Wrapper is allowed to launch the Java Application.

• wrapper.java.version.min (3.5.35)

  Specifies the minimum version of Java for which the Wrapper is allowed to launch the Java Application.

• wrapper.java.version.output (3.5.17)

  Displays the version of the JVM used by the Wrapper.

• wrapper.java.version.timeout (3.5.27)

  Configures the number of seconds allowed for the child process to print the JVM version before it is terminated.

• wrapper.registry.java_home (3.2.4)

  Specifies a registry key containing the path to the Java home folder.

• wrapper.registry.java_version (3.5.36) ( Std/Pro )

  Specifies a version of the JRE to use when locating the Java command from the Windows registry.