Delete old README.src.md
This commit is contained in:
Greg Turnquist
parent
59771e16c2
commit
ec71f23e3d
134
README.src.md
134
README.src.md
|
|
@ -1,134 +0,0 @@
|
|||
# Getting Started: Creating a Batch Service
|
||||
|
||||
What you'll build
|
||||
-----------------
|
||||
|
||||
This guide walks you through creating a basic batch-driven solution. You build a service that imports data from a CSV spreadsheet, transforms it with custom code, and stores the final results in a database.
|
||||
|
||||
What you'll need
|
||||
----------------
|
||||
|
||||
- About 15 minutes
|
||||
- {!include#prereq-editor-jdk-buildtools}
|
||||
|
||||
## {!include#how-to-complete-this-guide}
|
||||
|
||||
<a name="scratch"></a>
|
||||
Set up the project
|
||||
------------------
|
||||
{!include#build-system-intro}
|
||||
|
||||
{!include#create-directory-structure-hello}
|
||||
|
||||
### Create a Maven POM
|
||||
|
||||
{!include:initial/pom.xml}
|
||||
|
||||
{!include#bootstrap-starter-pom-disclaimer}
|
||||
|
||||
### Create business data
|
||||
|
||||
Typically your customer or a business analyst supplies a spreadsheet. In this case, you make it up.
|
||||
|
||||
`src/main/resources/sample-data.csv`
|
||||
```text
|
||||
Jill,Doe
|
||||
Joe,Doe
|
||||
Justin,Doe
|
||||
Jane,Doe
|
||||
John,Doe
|
||||
```
|
||||
|
||||
This spreadsheet contains a first name and a last name on each row, separated by a comma. This is a fairly common pattern that Spring handles out-of-the-box, as you will see.
|
||||
|
||||
### Define the destination for your data
|
||||
|
||||
Next, you write a SQL script to create a table to store the data.
|
||||
|
||||
{!include:complete/src/main/resources/schema.sql}
|
||||
|
||||
<a name="initial"></a>
|
||||
Create a business class
|
||||
-----------------------
|
||||
|
||||
Now that you see the format of data inputs and outputs, you write code to represent a row of data.
|
||||
|
||||
{!include:complete/src/main/java/hello/Person.java}
|
||||
|
||||
You can instantiate the `Person` class either with first and last name through a constructor, or by setting the properties.
|
||||
|
||||
Create an intermediate processor
|
||||
--------------------------------
|
||||
|
||||
A common paradigm in batch processing is to ingest data, transform it, and then pipe it out somewhere else. Here you write a simple transformer that converts the names to uppercase.
|
||||
|
||||
{!include:complete/src/main/java/hello/PersonItemProcessor.java}
|
||||
|
||||
`PersonItemProcessor` implements Spring Batch's `ItemProcessor` interface. This makes it easy to wire the code into a batch job that you define further down in this guide. According to the interface, you receive an incoming `Person` object, after which you transform it to an upper-cased `Person`.
|
||||
|
||||
> **Note:** There is no requirement that the input and output types be the same. In fact, after one source of data is read, sometimes the application's data flow needs a different data type.
|
||||
|
||||
Put together a batch job
|
||||
----------------------------
|
||||
|
||||
Now you put together the actual batch job. Spring Batch provides many utility classes that reduce the need to write custom code. Instead, you can focus on the business logic.
|
||||
|
||||
{!include:complete/src/main/java/hello/BatchConfiguration.java}
|
||||
|
||||
For starters, the `@EnableBatchProcessing` annotation adds many critical beans that support jobs and saves you a lot of leg work.
|
||||
|
||||
Break it down:
|
||||
|
||||
{!include:complete/src/main/java/hello/BatchConfiguration.java#reader-writer-processor}
|
||||
|
||||
The first chunk of code defines the input, processor, and output.
|
||||
- `reader()` creates an `ItemReader`. It looks for a file called `sample-data.csv` and parses each line item with enough information to turn it into a `Person`.
|
||||
- `processor()` creates an instance of our `PersonItemProcessor` you defined earlier, meant to uppercase the data.
|
||||
- `write(DataSource)` creates an `ItemWriter`. This one is aimed at a JDBC destination and automatically gets a copy of the dataSource created by `@EnableBatchProcessing`. It includes the SQL statement needed to insert a single `Person` driven by java bean properties.
|
||||
|
||||
The next chunk focuses on the actual job configuration.
|
||||
|
||||
{!include:complete/src/main/java/hello/BatchConfiguration.java#job-step}
|
||||
|
||||
The first method defines the job and the second one defines a single step. Jobs are built from steps, where each step can involve a reader, a processor, and a writer.
|
||||
|
||||
In this job definition, you need an incrementer because jobs use a database to maintain execution state. You then list each step, of which this job has only one step. The job ends, and the java API produces a perfectly configured job.
|
||||
|
||||
In the step definition, you define how much data to write at a time. In this case, it writes up to ten records at a time. Next, you configure the reader, processor, and writer using the injected bits from earlier.
|
||||
|
||||
> **Note:** chunk() is prefixed `<Person,Person>` because it's a generic method. This represents the input and output types of each "chunk" of processing, and lines up with `ItemReader<Person>` and `ItemWriter<Person>`.
|
||||
|
||||
Finally, you run the application.
|
||||
|
||||
{!include:complete/src/main/java/hello/BatchConfiguration.java#template-main}
|
||||
|
||||
This example uses a memory-based database (provided by `@EnableBatchProcessing`), meaning that when it's done, the data is gone. For demonstration purposes, there is extra code to create a `JdbcTemplate`, query the database, and print out the names of people the batch job inserts.
|
||||
|
||||
|
||||
Build an executable JAR
|
||||
-----------------------
|
||||
Add the following to your `pom.xml` file, keeping existing properties and plugins intact:
|
||||
|
||||
{!include:complete/pom.xml#shade-config}
|
||||
|
||||
Create a single executable JAR file containing all necessary dependency classes:
|
||||
|
||||
$ mvn package
|
||||
|
||||
|
||||
Run the batch job
|
||||
-----------------
|
||||
|
||||
Now you can run the job from the JAR as well, and distribute that as an executable artifact:
|
||||
|
||||
$ java -jar target/gs-batch-processing-complete-0.1.0.jar
|
||||
|
||||
|
||||
The job prints out a line for each person that gets transformed. After the job runs, you can also see the output from querying the database.
|
||||
|
||||
Summary
|
||||
-------
|
||||
|
||||
Congratulations! You built a batch job that ingested data from a spreadsheet, processed it, and wrote it to a database.
|
||||
|
||||
[zip]: https://github.com/springframework-meta/gs-batch-processing/archive/master.zip
|
||||
Loading…
Reference in New Issue