Table of contents
introduction
Next to the previous article: Spring Batch step object-return status-ExitStatus , after understanding the return status ExitStatus status class, let’s learn about the core data table of Spring Batch batch processing
overview
In the learning phase, Spring Batch data storage can be stored in two ways, 1: H2 memory database 2: relational database. Choice 1 is easy to say, basically we don’t need to do too much intervention, and choice 2 is the same, but we can use the database visualization tool to view the data table to help us better understand the execution process or principle of springbatch.
When we choose the database method to store batch data, Spring Batch will automatically create 9 tables at startup, storing them respectively: JobExecution, JobContext, JobParameters, JobInstance, JobExecution id sequence, Job id sequence, StepExecution, StepContext/ChunkContext, StepExecution id sequence and other objects. Spring Batch provides the JobRepository component to implement CRUD operations on these tables, and these operations are basically encapsulated in steps, blocks, and job api operations, which do not require us to intervene too much, so just understand the content of this chapter.
batch_job_instance table
When the job is executed for the first time, a unique JobInstance object will be generated according to the job name and identification parameters, and the batch_job_instance table will record a message representing the job instance.
| field | describe |
|---|---|
| JOB_INSTANCE_ID | Job Instance Primary Key |
| VERSION | The version number controlled by optimistic locking |
| JOB_NAME | job name |
| JOB_KEY | The hash value of the job name and identifying parameters can uniquely identify a job instance |
batch_job_execution table
Every time a job is started, a JobExecution object is created, which represents a job execution, and the object record is stored in the batch_job_execution table.
| field | describe |
|---|---|
| JOB_EXECUTION_ID | job execution object primary key |
| VERSION | The version number controlled by optimistic locking |
| JOB_INSTANCE_ID | JobInstanceId (which JobInstance belongs to) |
| CREATE_TIME | record creation time |
| START_TIME | Job execution start time |
| END_TIME | Job execution end time |
| STATUS | Batch status of job execution |
| EXIT_CODE | The exit code of the job execution |
| EXIT_MESSAGE | Exit message for job execution |
| LAST_UPDATED | The time the record was last updated |
batch_job_execution_context表
batch_job_execution_context is used to save the ExecutionContext object data corresponding to the JobContext.
| field | describe |
|---|---|
| JOB_EXECUTION_ID | job execution object primary key |
| SHORT_CONTEXT | ExecutionContext string reduced version after serialization |
| SERIALIZED_CONTEXT | ExecutionContext string after serialization |
batch_job_execution_params表
When the job is started, use the location where the identifying parameters are saved: batch_job_execution_params, one parameter and one record
| field | describe |
|---|---|
| JOB_EXECUTION_ID | job execution object primary key |
| TYPE_CODE | tag parameter type |
| KEY_NAME | parameter name |
| STRING_VALUE | There is a value when the parameter type is String |
| DATE_VALUE | There is a value when the parameter type is Date |
| LONG_VAL | There is a value when the parameter type is LONG |
| DOUBLE_VAL | There is a value when the parameter type is DOUBLE |
| IDENTIFYING | Used to mark whether the parameter is an identifying parameter |
btch_step_execution表
Job starts, steps are executed, and the execution information of each step is saved in the tch_step_execution table
| field | describe |
|---|---|
| STEP_EXECUTION_ID | step execution object id |
| VERSION | Optimistic locking control version number |
| STEP_NAME | step name |
| JOB_EXECUTION_ID | job execution object id |
| START_TIME | The start time of the step execution |
| END_TIME | The end time of the step execution |
| STATUS | Step Batch Status |
| COMMIT_COUNT | Number of transactions committed in step execution |
| READ_COUNT | Number of entries read |
| FILTER_COUNT | The number of entries filtered out because the ItemProcessor returned null |
| WRITE_COUNT | Number of entries written |
| READ_SKIP_COUNT | The number of items skipped due to an exception thrown in the ItemReader |
| PROCESS_SKIP_COUNT | The number of items skipped due to an exception thrown in the ItemProcessor |
| WRITE_SKIP_COUNT | The number of entries skipped due to an exception thrown in the ItemWriter |
| ROLLBACK_COUNT | Number of transactions rolled back during step execution |
| EXIT_CODE | the step's exit code |
| EXT_MESSAGE | Information returned by step execution |
| LAST_UPDATE | Last updated record time |
batch_step_execution_context表
The data table saved by the ExecutionContext corresponding to the StepContext object: batch_step_execution_context
| field | describe |
|---|---|
| STEP_EXECUTION_ID | step execution object id |
| SHORT_CONTEXT | ExecutionContext string reduced version after serialization |
| SERIALIZED_CONTEXT | ExecutionContext string after serialization |
H2 in-memory database
The operation of the job refers to the control of the job, including job start, job stop, job exception handling, job restart processing, and so on.
At this point, this article is over. If you want to know what will happen next, please listen to the next chapter to break it down~
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