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1. Overview

Spring JDBC and JPA provide abstractions over native JDBC APIs, allowing developers to do away with native SQL queries. However, we often need to see those auto-generated SQL queries and the order in which they were executed for debugging purposes.

In this quick tutorial, we're going to look at different ways of logging these SQL queries in Spring Boot.

Further reading:

Spring JDBC

Introduction to the Spring JDBC abstraction, with example on how to use the JbdcTempalte and NamedParameterJdbcTemplate APIs.

Introduction to Spring Data JPA

Introduction to Spring Data JPA with Spring 4 - the Spring config, the DAO, manual and generated queries and transaction management.

Hibernate Interceptors

A quick and practical guide to creating Hibernate interceptors.

2. Logging JPA Queries

2.1. To Standard Output

The simplest way to dump the queries to standard out is to add the following to application.properties:

spring.jpa.show-sql=true

To beautify or pretty print the SQL, we can add:

spring.jpa.properties.hibernate.format_sql=true

While this is extremely simple, it's not recommended, as it directly unloads everything to standard output without any optimizations of a logging framework.

Moreover, it doesn't log the parameters of prepared statements.

2.2. Via Loggers

Now let's see how we can log the SQL statements by configuring loggers in the properties file:

logging.level.org.hibernate.SQL=DEBUG
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=TRACE

The first line logs the SQL queries, and the second statement logs the prepared statement parameters.

The pretty print property will work in this configuration as well.

By setting these properties, logs will be sent to the configured appender. By default, Spring Boot uses logback with a standard out appender.

3. Logging JdbcTemplate Queries

To configure statement logging when using JdbcTemplate, we need the following properties:

logging.level.org.springframework.jdbc.core.JdbcTemplate=DEBUG
logging.level.org.springframework.jdbc.core.StatementCreatorUtils=TRACE

Similar to the JPA logging configuration, the first line is for logging statements and the second is to log parameters of prepared statements.

4. How Does It Work?

The Spring/Hibernate classes, which generate SQL statements and set the parameters, already contain the code for logging them.

However, the level of those log statements is set to DEBUG and TRACE respectively, which is lower than the default level in Spring Boot — INFO.

By adding these properties, we are just setting those loggers to the required level.

5. Conclusion

In this short article, we've looked at the ways to log SQL queries in Spring Boot.

If we choose to configure multiple appenders, we can also separate SQL statements and other log statements into different log files to keep things clean.

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