Table of Contents

• What You Will Build
• What You Need
• Starting with Spring Initializr
• Create a Booking Service
• Build an Application
• Summary
• See Also

This guide walks you through the process of wrapping database operations with non-intrusive transactions.

What You Will Build

You will build a simple JDBC application wherein you make database operations transactional without having to write specialized JDBC code.

What You Need

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Starting with Spring Initializr

You can use this pre-initialized project and click Generate to download a ZIP file. This project is configured to fit the examples in this tutorial.

To manually initialize the project:

1. Navigate to https://start.spring.io. This service pulls in all the dependencies you need for an application and does most of the setup for you.

2. Choose either Gradle or Maven and the language you want to use. This guide assumes that you chose Java.

3. Click Dependencies and select Spring Data JDBC and H2 Database.

4. Click Generate.

5. Download the resulting ZIP file, which is an archive of a web application that is configured with your choices.

Note	If your IDE has the Spring Initializr integration, you can complete this process from your IDE.

Note	You can also fork the project from Github and open it in your IDE or other editor.

Create a Booking Service

First, you need to use the BookingService class to create a JDBC-based service that books people into the system by name. The following listing (from src/main/java/com/example/managingtransactions/BookingService.java) shows how to do so:

link:complete/src/main/java/com/example/managingtransactions/BookingService.java[role=include]

The code has an autowired JdbcTemplate, a handy template class that does all the database interactions needed by the remaining code.

You also have a book method that can book multiple people. It loops through the list of people and, for each person, inserts that person into the BOOKINGS table by using the JdbcTemplate. This method is tagged with @Transactional, meaning that any failure causes the entire operation to roll back to its previous state and to re-throw the original exception. This means that none of the people are added to BOOKINGS if one person fails to be added.

You also have a findAllBookings method to query the database. Each row fetched from the database is converted into a String, and all the rows are assembled into a List.

Build an Application

The Spring Initializr provides an application class. In this case, you need not modify this application class. The following listing (from src/main/java/com/example/managingtransactions/ManagingTransactionsApplication.java) shows the application class

link:complete/src/main/java/com/example/managingtransactions/ManagingTransactionsApplication.java[role=include]

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Your application actually has zero configuration. Spring Boot detects spring-jdbc and h2 on the classpath and automatically creates a DataSource and a JdbcTemplate for you. Because this infrastructure is now available and you have no dedicated configuration, a DataSourceTransactionManager is also created for you. This is the component that intercepts the method annotated with @Transactional (for example, the book method on BookingService). The BookingService is detected by classpath scanning.

Another Spring Boot feature demonstrated in this guide is the ability to initialize the schema on startup. The following file (from src/main/resources/schema.sql) defines the database schema:

link:complete/src/main/resources/schema.sql[role=include]

There is also a CommandLineRunner that injects the BookingService and showcases various transactional use cases. The following listing (from src/main/java/com/example/managingtransactions/AppRunner.java) shows the command line runner:

link:complete/src/main/java/com/example/managingtransactions/AppRunner.java[role=include]

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You should see the following output:

2019-09-19 14:05:25.111  INFO 51911 --- [           main] c.e.m.ManagingTransactionsApplication    : Starting ManagingTransactionsApplication on Jays-MBP with PID 51911 (/Users/j/projects/guides/gs-managing-transactions/complete/target/classes started by j in /Users/j/projects/guides/gs-managing-transactions/complete)
2019-09-19 14:05:25.114  INFO 51911 --- [           main] c.e.m.ManagingTransactionsApplication    : No active profile set, falling back to default profiles: default
2019-09-19 14:05:25.421  INFO 51911 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data repositories in DEFAULT mode.
2019-09-19 14:05:25.438  INFO 51911 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 13ms. Found 0 repository interfaces.
2019-09-19 14:05:25.678  INFO 51911 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2019-09-19 14:05:25.833  INFO 51911 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2019-09-19 14:05:26.158  INFO 51911 --- [           main] c.e.m.ManagingTransactionsApplication    : Started ManagingTransactionsApplication in 1.303 seconds (JVM running for 3.544)
2019-09-19 14:05:26.170  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking Alice in a seat...
2019-09-19 14:05:26.181  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking Bob in a seat...
2019-09-19 14:05:26.181  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking Carol in a seat...
2019-09-19 14:05:26.195  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : Alice, Bob and Carol have been booked
2019-09-19 14:05:26.196  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking Chris in a seat...
2019-09-19 14:05:26.196  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking Samuel in a seat...
2019-09-19 14:05:26.271  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : v--- The following exception is expect because 'Samuel' is too big for the DB ---v
2019-09-19 14:05:26.271 ERROR 51911 --- [           main] c.e.managingtransactions.AppRunner       : PreparedStatementCallback; SQL [insert into BOOKINGS(FIRST_NAME) values (?)]; Value too long for column """FIRST_NAME"" VARCHAR(5) NOT NULL": "'Samuel' (6)"; SQL statement:
insert into BOOKINGS(FIRST_NAME) values (?) [22001-199]; nested exception is org.h2.jdbc.JdbcSQLDataException: Value too long for column """FIRST_NAME"" VARCHAR(5) NOT NULL": "'Samuel' (6)"; SQL statement:
insert into BOOKINGS(FIRST_NAME) values (?) [22001-199]
2019-09-19 14:05:26.271  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : So far, Alice is booked.
2019-09-19 14:05:26.271  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : So far, Bob is booked.
2019-09-19 14:05:26.271  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : So far, Carol is booked.
2019-09-19 14:05:26.271  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : You shouldn't see Chris or Samuel. Samuel violated DB constraints, and Chris was rolled back in the same TX
2019-09-19 14:05:26.272  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking Buddy in a seat...
2019-09-19 14:05:26.272  INFO 51911 --- [           main] c.e.managingtransactions.BookingService  : Booking null in a seat...
2019-09-19 14:05:26.273  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : v--- The following exception is expect because null is not valid for the DB ---v
2019-09-19 14:05:26.273 ERROR 51911 --- [           main] c.e.managingtransactions.AppRunner       : PreparedStatementCallback; SQL [insert into BOOKINGS(FIRST_NAME) values (?)]; NULL not allowed for column "FIRST_NAME"; SQL statement:
insert into BOOKINGS(FIRST_NAME) values (?) [23502-199]; nested exception is org.h2.jdbc.JdbcSQLIntegrityConstraintViolationException: NULL not allowed for column "FIRST_NAME"; SQL statement:
insert into BOOKINGS(FIRST_NAME) values (?) [23502-199]
2019-09-19 14:05:26.273  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : So far, Alice is booked.
2019-09-19 14:05:26.273  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : So far, Bob is booked.
2019-09-19 14:05:26.273  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : So far, Carol is booked.
2019-09-19 14:05:26.273  INFO 51911 --- [           main] c.e.managingtransactions.AppRunner       : You shouldn't see Buddy or null. null violated DB constraints, and Buddy was rolled back in the same TX

The BOOKINGS table has two constraints on the first_name column:

• Names cannot be longer than five characters.

• Names cannot be null.

The first three names inserted are Alice, Bob, and Carol. The application asserts that three people were added to that table. If that had not worked, the application would have exited early.

Next, another booking is done for Chris and Samuel. Samuel’s name is deliberately too long, forcing an insert error. Transactional behavior stipulates that both Chris and Samuel (that is, all the values in this transaction) should be rolled back. Thus, there should still be only three people in that table, which the assertion demonstrates.

Finally, Buddy and null are booked. As the output shows, null causes a rollback as well, leaving the same three people booked.

Summary

Congratulations! You have just used Spring to develop a simple JDBC application wrapped with non-intrusive transactions.

See Also

The following guides may also be helpful:

• Building an Application with Spring Boot

• Accessing Data with JPA

• Accessing Data with MongoDB

• Accessing data with MySQL

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