Getting started 

Summary 

This guide explains how to set up your development environment and introduces the basic functionality of Doma.

Install JDK 

First, you need to install JDK 17 or later.

Get sample project 

To get the sample project, clone the getting-started repository and navigate to the created directory using these commands:

$ git clone https://github.com/domaframework/getting-started.git
$ cd getting-started

Ensure successful project setup with:

$ ./gradlew build

Note

For Windows users, execute gradlew build.

Sample project structure 

The getting-started sample is a Gradle multi-project containing a java-17 subproject. In this guide, we’ll focus on the java-17 subproject.

Import project to your IDE 

Eclipse 

This guide has been tested with Eclipse 4.23.0. Import the getting-started project as a Gradle project.

Note

If you want to store SQL statements in files, Doma Tools can help you.

IntelliJ IDEA 

Tested with IntelliJ IDEA Community 2023.3.4. Import the getting-started project as a Gradle project.

Note

You can use the following IntelliJ IDEA plugins to support Doma. Since they have overlapping features, please choose one:

Programming styles 

Doma supports two programming styles: DSL and DAO. We recommend using both styles together to maximize their benefits.

The DSL style uses a type-safe Criteria API, which excels at automatically generating simple dynamic SQL. The DAO style maps SQL statements to Java interface methods and works well for both automatically generating standard SQL for insert, update, and delete operations and for writing complex SQL manually.

DSL style 

In the DSL style, you work with examples in the boilerplate.java17.repository.EmployeeRepository and the Unified Criteria API for operations.

SELECT 

To execute a SELECT query and retrieve Java object results, follow this example:

public Employee selectById(Integer id) {
  var e = new Employee_();
  return queryDsl.from(e).where(c -> c.eq(e.id, id)).fetchOne();
}

You’ll use a metamodel class, like Employee_ for Employee, which is auto-generated through annotation processing.

The queryDsl instance from the QueryDsl class serves as the Criteria API’s starting point.

The above code generates the following SQL statement:

select t0_.id, t0_.name, t0_.age, t0_.version from Employee t0_ where t0_.id = ?

DELETE 

To issue a DELETE statement, write as follows:

public void delete(Employee employee) {
  var e = new Employee_();
  queryDsl.delete(e).single(employee).execute();
}

INSERT 

To issue an INSERT statement, write as follows:

public void insert(Employee employee) {
  var e = new Employee_();
  queryDsl.insert(e).single(employee).execute();
}

UPDATE 

To issue an UPDATE statement, write as follows:

public void update(Employee employee) {
  var e = new Employee_();
  queryDsl.update(e).single(employee).execute();
}

DAO style 

You can find some examples in boilerplate.java17.dao.EmployeeDao. See DAO interfaces and SQL templates for more information.

SELECT (DAO)

In the DAO style, for issuing a SELECT statement to retrieve Java objects, use the @Sql annotation with Text Blocks for SQL templates:

@Sql("""
    select
      /*%expand*/*
    from
      employee
    where
      id = /* id */0
    """)
@Select
Employee selectById(Integer id);

This SQL template contains two special expressions: /*%expand*/ and /* id */. When processing the SQL template, /*%expand*/ and the following * are replaced with a complete column list. Similarly, /* id */ and the following 0 are replaced with the bind variable ?. The value bound to this variable is the id parameter of the selectById method.

The above code generates the following SQL statement:

select
  id, name, age, version
from
  employee
where
  id = ?

DELETE (DAO)

To issue a DELETE statement, write as follows:

@Delete
int delete(Employee employee);

INSERT (DAO)

To issue an INSERT statement, write as follows:

@Insert
int insert(Employee employee);

UPDATE (DAO)

To issue an UPDATE statement, write as follows:

@Update
int update(Employee employee);

Next Step 

See other example projects:

simple-examples