java-wrappers - capacities shared by java wrapper scripts
Most Java programs are not run directly, but through small shell scripts that take care of various things, such as finding a suitable Java environment and looking for libraries.
To ease the task of the maintainers, they rely on a library providing runtime detection, library detection and other features. This manual page describes the common features of all those scripts, and to which point you can configure them. This is mainly done via environment variables.
java-wrappers understands some environment variables:
- The java command that will be run. If this variable is set, it disables all lookup for a java runtime.
- Specifies a directory that will be looked for a java or a jdb executable (depending on the setting of JAVA_DEBUGGER). It has precedence over JAVA_HOME but not over JAVA_CMD.
- A path to a Java runtime. If this variable is set, all lookup for a Java runtime is disabled, except that if no java executable is found in the path, the command java is used.
- A probably more easy-to-use version of the JAVA_HOME variable: instead of specifying the full path of the Java runtime, you name it. List of available flavors can be found in the file /usr/lib/java-wrappers/jvm-list.sh. See examples below.
- If this is set, the wrapper will try to pick up a Java debugger rather than a Java interpreter. This will fail if the jbd of the runtime found is a stub.
- Additional classpath, will have priority over the one found by the wrapper.
- Additional arguments to the java command. They will come before all other arguments.
- If this variable is set, it will be the only classpath. You'd better know what you are doing.
- This is probably the most important variable; if it set, the wrapper will print out useful information as it goes by its business, such as which runtime it did find, and which command is run eventually.
- The path where the wrappers will go looking for jar archives. If not set, the wrapper will look into the default directory, /usr/share/java. Warning : the wrapper will not look anywhere else than in JAVA_JARPATH. Setting it incorrectly will most probably result in early crashes.
The examples all rely on rasterizer(1), from the package libbatik-java, but they really apply to all scripts that use java-wrappers.
Print out debugging information:
Limit rasterizer's memory to 80 MB:
Force rasterizer to run with kaffe(1):
The same, but using JAVA_BINDIR:
Force rasterizer to run with openjdk:
Debug rasterizer with Sun's debugger, while printing debugging information from the wrapper:
DEBUG_WRAPPER=1 JAVA_CMD=/usr/lib/jvm/java-6-sun/bin/jdb rasterizer
Care has been taken to make the wrappers bug-free. If that was not the case, please file a bug report against the java-wrappers package.
If you wish to submit any problem with a Java executable relying on java-wrappers, please also submit the output of the command run with DEBUG_WRAPPER=1. It will save one mail exchange and therefore potentially reduce the time it takes to fix the bug.
There is currently no documentation about writing a wrapper script save the comments in /usr/lib/java-wrappers/java-wrappers.sh. If you have to write one, we suggest you base yourself upon, for instance, the rasterizer wrapper script, or any other one (just pick up any direct reverse dependency of java-wrappers and look for scripts).
java-wrappers and its documentation were written by Vincent Fourmond <email@example.com>