10 January 2020

Logging for real SQL queries is very important in case using any ORM solution, - as you never can be sure which and how many requests will send JPA provider to do find, merge, query or some other operation.

Wildfly uses Hibernate as JPA provider and provides few standard ways to enable SQL logging:

1. Add hibernate.show_sql property to your persistence.xml :

<properties>
    ...
    <property name="hibernate.show_sql" value="true" />
    ...
</properties>
INFO  [stdout] (default task-1) Hibernate: insert into blogentity (id, body, title) values (null, ?, ?)
INFO  [stdout] (default task-1) Hibernate: select blogentity0_.id as id1_0_, blogentity0_.body as body2_0_, blogentity0_.title as title3_0_ from blogentity blogentity0_ where blogentity0_.title=?

2. Enable ALL log level for org.hibernate category like:

/subsystem=logging/periodic-rotating-file-handler=sql_handler:add(level=ALL, file={"path"=>"sql.log"}, append=true, autoflush=true, suffix=.yyyy-MM-dd,formatter="%d{yyyy-MM-dd HH:mm:ss,SSS}")
/subsystem=logging/logger=org.hibernate.SQL:add(use-parent-handlers=false,handlers=["sql_handler"])
/subsystem=logging/logger=org.hibernate.type.descriptor.sql.BasicBinder:add(use-parent-handlers=false,handlers=["sql_handler"])
DEBUG [o.h.SQL] insert into blogentity (id, body, title) values (null, ?, ?)
TRACE [o.h.t.d.s.BasicBinder] binding parameter [1] as [VARCHAR] - [this is body]
TRACE [o.h.t.d.s.BasicBinder] binding parameter [2] as [VARCHAR] - [title]
DEBUG [o.h.SQL] select blogentity0_.id as id1_0_, blogentity0_.body as body2_0_, blogentity0_.title as title3_0_ from blogentity blogentity0_ where blogentity0_.title=?
TRACE [o.h.t.d.s.BasicBinder] binding parameter [1] as [VARCHAR] - [title]

3. Enable spying of SQL statements:

/subsystem=datasources/data-source=ExampleDS/:write-attribute(name=spy,value=true)
/subsystem=logging/logger=jboss.jdbc.spy/:add(level=DEBUG)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [DataSource] getConnection()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [Connection] prepareStatement(insert into blogentity (id, body, title) values (null, ?, ?), 1)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [PreparedStatement] setString(1, this is body)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [PreparedStatement] setString(2, title)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [PreparedStatement] executeUpdate()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [PreparedStatement] getGeneratedKeys()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] next()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] getMetaData()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] getLong(1)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] close()
...
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [DataSource] getConnection()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [Connection] prepareStatement(select blogentity0_.id as id1_0_, blogentity0_.body as body2_0_, blogentity0_.title as title3_0_ from blogentity blogentity0_ where blogentity0_.title=?)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [PreparedStatement] setString(1, title)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [PreparedStatement] executeQuery()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] next()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] getLong(id1_0_)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] wasNull()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] getString(body2_0_)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] wasNull()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] getString(title3_0_)
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] wasNull()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] next()
DEBUG [j.j.spy] java:jboss/datasources/ExampleDS [ResultSet] close()

So, from above we can see that variants 2 and 3 is most useful as allows to log queries with parameters. From other point of view - SQL logging can generate lot of unneeded debug information on production. To avoid garbage data in your log files, feel free to use Filter Expressions for Logging