Basic launcher for starting jobs from the command line. In general, it is
assumed that this launcher will primarily be used to start a job via a script
from an Enterprise Scheduler. Therefore, exit codes are mapped to integers so
that schedulers can use the returned values to determine the next course of
action. The returned values can also be useful to operations teams in
determining what should happen upon failure. For example, a returned code of
5 might mean that some resource wasn't available and the job should be
restarted. However, a code of 10 might mean that something critical has
happened and the issue should be escalated.
With any launch of a batch job within Spring Batch, a Spring context
containing the
Job and some execution context has to be created. This
command line launcher can be used to load the job and its context from a
single location. All dependencies of the launcher will then be satisfied by
autowiring by type from the combined application context. Default values are
provided for all fields except the
JobLauncher and
JobLocator. Therefore, if autowiring fails to set it (it should be noted that
dependency checking is disabled because most of the fields have default
values and thus don't require dependencies to be fulfilled via autowiring)
then an exception will be thrown. It should also be noted that even if an
exception is thrown by this class, it will be mapped to an integer and
returned.
Notice a property is available to set the
SystemExiter. This class is
used to exit from the main method, rather than calling System.exit()
directly. This is because unit testing a class the calls System.exit() is
impossible without kicking off the test within a new JVM, which it is
possible to do, however it is a complex solution, much more so than
strategizing the exiter.
The arguments to this class can be provided on the command line (separated by
spaces), or through stdin (separated by new line). They are as follows:
jobPath <options> jobIdentifier (jobParameters)
The command line options are as follows
- jobPath: the xml application context containing a
Job
- -restart: (optional) to restart the last failed execution
- -stop: (optional) to stop a running execution
- -abandon: (optional) to abandon a stopped execution
- -next: (optional) to start the next in a sequence according to the
JobParametersIncrementer in the
Job
- jobIdentifier: the name of the job or the id of a job execution (for
-stop, -abandon or -restart).
- jobParameters: 0 to many parameters that will be used to launch a job
specified in the form of
key=value
pairs.
If the -next
option is used the parameters on the command line
(if any) are appended to those retrieved from the incrementer, overriding any
with the same key.
The combined application context must contain only one instance of
JobLauncher. The job parameters passed in to the command line will be
converted to
Properties by assuming that each individual element is
one parameter that is separated by an equals sign. For example,
"vendor.id=290232". The resulting properties instance is converted to
JobParameters using a
JobParametersConverter from the
application context (if there is one, or a
DefaultJobParametersConverter otherwise). Below is an example
arguments list: "
java org.springframework.batch.core.launch.support.CommandLineJobRunner testJob.xml
testJob schedule.date=2008/01/24 vendor.id=3902483920
Once arguments have been successfully parsed, autowiring will be used to set
various dependencies. The
JobLauncher for example, will be
loaded this way. If none is contained in the bean factory (it searches by
type) then a
BeanDefinitionStoreException will be thrown. The same
exception will also be thrown if there is more than one present. Assuming the
JobLauncher has been set correctly, the jobIdentifier argument will be used
to obtain an actual
Job. If a
JobLocator has been set, then
it will be used, if not the beanFactory will be asked, using the
jobIdentifier as the bean id.