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JDBI integration¶

Extensions project module

Integrates JDBI2 with guice. Based on dropwizard-jdbi integration.

Features:

DBI instance available for injection
Introduce unit of work concept, which is managed by annotations and guice aop (very like spring's @Transactional)
Repositories (JDBI proxies for interfaces and abstract classes):
- installed automatically (when classpath scan enabled)
- are normal guice beans, supporting aop and participating in global (thread bound) transaction.
- no need to compose repositories anymore (e.g. with @CreateSqlObject) to gain single transaction.
Automatic installation for custom ResultSetMapper

Added installers:

RepositoryInstaller - sql proxies
MapperInstaller - result set mappers

Setup¶

Avoid version in dependency declaration below if you use extensions BOM.

Maven:

<dependency>
  <groupId>ru.vyarus.guicey</groupId>
  <artifactId>guicey-jdbi</artifactId>
  <version>0.7.0</version>
</dependency>

Gradle:

compile 'ru.vyarus.guicey:guicey-jdbi:0.7.0'

See the most recent version in the badge above.

Usage¶

Register bundle:

GuiceBundle.builder()        
        .bundles(JdbiBundle.<ConfType>forDatabase((conf, env) -> conf.getDatabase()))
        ...

Here default DBI instance will be created from database configuration (much like it's described in dropwizard documentation).

Or build DBI instance yourself:

JdbiBundle.forDbi((conf, env) -> locateDbi())

Unit of work¶

Unit of work concept states for: every database related operation must be performed inside unit of work.

In DBI such approach was implicit: you were always tied to initial handle. This lead to cumbersome usage of sql object proxies: if you create it on-demand it would always create new handle; if you want to combine multiple objects in one transaction, you have to always create them manually for each transaction.

Integration removes these restrictions: dao (repository) objects are normal guice beans and transaction scope is controlled by @InTransaction annotation (note that such name was intentional to avoid confusion with DBI own's Transaction annotation and more common Transactional annotations).

At the beginning of unit of work, DBI handle is created and bound to thread (thread local). All repositories are simply using this bound handle and so share transaction inside unit of work.

@InTransaction¶

Annotation on method or class declares transactional scope. For example:

@Inject MyDAO dao

@InTransaction
public Result doSomething() {
   dao.select();
   ...
}

Transaction opened before doSomething() method and closed after it. Dao call is also performed inside transaction. If exception appears during execution, it's propagated and transaction rolled back.

Nested annotations are allowed (they simply ignored).

Note that unit of work is not the same as transaction scope (transaction scope could be less or equal to unit of work). But, for simplicity, you may think of it as the same things, if you always use @InTransaction annotation.

If required, you may use your own annotation for transaction definition:

JdbiBundle.forDatabase((conf, env) -> conf.getDatabase())
    .withTxAnnotations(MyCustomTransactional.class);

Note that this will override default annotation support. If you want to support multiple annotations then specify all of them:

JdbiBundle.forDatabase((conf, env) -> conf.getDatabase())
    .withTxAnnotations(InTransaction.class, MyCustomTransactional.class);

Context Handle¶

Inside unit of work you may reference current handle by using:

@Inject Provider<Handle>

Manual transaction definition¶

You may define transaction (with unit of work) without annotation using:

@Inject TransactionTenpate template;
...
template.inTrabsansaction((handle) -> doSomething())

Note that inside such manual scope you may also call any repository bean, as it's absolutely the same definition as with annotation.

Repository¶

Declare repository (interface or abstract class) as usual, using DBI annotations. It only must be annotated with @JdbiRepository so installer could recognize it and register in guice context.

Singleton scope will be forced for repositories.

@JdbiRepository
@InTransaction
public interface MyRepository {     

    @SqlQuery("select name from something where id = :id")
    String findNameById(@Bind("id") int id);
}

Note the use of @InTransaction: it was used to be able to call repository methods without extra annotations (the lowest transaction scope it's repository itself). It will make beans "feel the same" as usual DBI on demand sql object proxies.

@InTransaction annotation is handled using guice aop. You can use any other guice aop related features.

You can also use injection inside repositories, but only field injection:

public abstract class MyRepo {
    @Inject SomeBean bean;
}

Constructor injection is impossible, because DBI sql proxies are still used internally and DBI will not be able to construct proxy for class with constructor injection.

Don't use DBI @Transaction and @CreateSqlObject annotations anymore: probably they will even work, but they are not needed now and may confuse.

All installed repositories are reported into console:

INFO  [2016-12-05 19:42:27,374] ru.vyarus.guicey.jdbi.installer.repository.RepositoryInstaller: repositories = 

    (ru.vyarus.guicey.jdbi.support.repository.SampleRepository)

Result set mapper¶

If you have custom implementations of ResultSetMapper, it may be registered automatically. You will be able to use injections there because mappers become ususal guice beans (singletons). When classpath scan is enabled, such classes will be searched and installed automatically.

public class CustomMapper implements ResutlSetMapper<Custom> {
    @Override
    public Cusom map(int row, ResultSet rs, StatementContext ctx) {
        // mapping here
        return custom;
    }
}

And now Custom type could be used for queries:

@JdbiRepository
@InTransaction
public interface CustomRepository {     

    @SqlQuery("select * from custom where id = :id")
    Custom findNameById(@Bind("id") int id);
}

All installed mappers are reported to console:

INFO  [2016-12-05 20:02:25,399] ru.vyarus.guicey.jdbi.installer.MapperInstaller: jdbi mappers = 

    Sample               (ru.vyarus.guicey.jdbi.support.mapper.SampleMapper)

Manual unit of work definition¶

If, for some reason, you don't need transaction at some place, you can declare raw unit of work and use assigned handle directly:

@Inject UnitManager manager;

manager.beginUnit();
try {
    Handle handle = manager.get();
    // logic executed in unit of work but without transaction
} finally {
    manager.endUnit();
}

Repositories could also be called inside such manual unit (as unit of work is correctly started).