Spring-JDBC-ROMA

What is Spring-JDBC-ROMA?

Spring-JDBC-ROMA is a rowmapper extension for Spring-JDBC module. There is already a rowmapper named "org.springframework.jdbc.core.BeanPropertyRowMapper" for binding resultset attributes to object. But it is reflection based and can cause performance problems as Spring developers said. However Spring-JDBC-ROMA is not reflection based and it is byte code generation (with CGLib and Javassist) based rowmapper. It generates rowmapper on the fly like implementing as manual so it has no performance overhead. It also supports object relations as lazy and eager. There are other lots of interesting features and these features can be customized with developer's extended classes.

What features does Spring-JDBC-ROMA have?

All primitive types, enums, dates, collections, blob, clob and complex objects are supported.
Lazy or eager field accessing is supported.
Writing your custom field based RowMapperFieldGenerator implementations is supported.
Writing your custom class (or type) based RowMapperFieldGeneratorFactory implementations is supported.
Writing field access definitions as compilable Java code in annotation or configuration file (XML file, properties file, ...) is supported.

Install

In your pom.xml, you must add repository and dependency for Spring-JDBC-ROMA. You can change spring.jdbc.roma.version to any existing spring-jdbc-roma library version.

...
<properties>
    ...
    <spring.jdbc.roma.version>1.0.0-RELEASE</spring.jdbc.roma.version>
    ...
</properties>
...
<dependencies>
    ...
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc-roma</artifactId>
        <version>${spring.jdbc.roma.version}</version>
    </dependency>
    ...
</dependencies>
...
<repositories>
    ...
    <repository>
        <id>serkanozal-maven-repository</id>
        <url>https://github.com/serkan-ozal/maven-repository/raw/master/</url>
    </repository>
    ...
</repositories>
...

And finally, in your Spring context xml file add following configuration to make your Spring context automatically aware of Spring-JDBC-ROMA.

...
<import resource="classpath*:roma-context.xml"/>
...

Spring-JDBC-ROMA with a simple example

Here is User class:

public class User {

    @RowMapperField(columnName = "id")
    private Long id;
    @RowMapperField(columnName = "username")
    private String username;
    @RowMapperField(columnName = "password")
    private String password;
    @RowMapperField(columnName = "firstname")
    private String firstname;
    @RowMapperField(columnName = "lastname")
    private String lastname;
    @RowMapperField(columnName = "enabled")
    private boolean enabled = true;
    @RowMapperField(columnName = "gender")
    private Gender gender;
    @RowMapperObjectField(
        provideViaSpringProvider = 
            @RowMapperSpringProvider(
                provideCode = "@{roleDAO}.getUserRoleList(${id})"),
        lazy = true)
    private List<Role> roles = new ArrayList<Role>();

    ...

}

Here is Role class:

public class Role {

    @RowMapperField(columnName = "id")
    private Long id;
    @RowMapperField(columnName = "name")
    private String name;
    @RowMapperObjectField(
        provideViaSpringProvider = 
            @RowMapperSpringProvider(
                provideCode = "@{permissionDAO}.getRolePermissionList(${id})"),
        lazy = true)
    private List<Permission> permissions = new ArrayList<Permission>();

    ...

}

You can get User entity rowmapper as follows:

@Autowired
RowMapperService rowMapperService;

...

RowMapper<User> userRowMapper = rowMapperService.getRowMapper(User.class);

In this example, we can get related Role entites of User entity with "@RowMapperObjectField" annotion automatically. We use "@RowMapperObjectField" annotation for accessing related Role entites of User entity with id attribute of User. We have "lazy=true" configuration, since roles field are initialized while we are accessing it first time. If we don't access it, it will not be set.

In addition, we can define User entity with compilable pure Java code as follows:

public class User {

    ...

    @RowMapperObjectField(
        provideViaImplementationProvider = 
            @RowMapperImplementationProvider(
                provideCode = "RoleDAO.getUserRoleListAsStaticMethod(${id})", 
                usedClasses = {RoleDAO.class}), 
        lazy = true)
    private List<Role> roles = new ArrayList<Role>();

    ...

}

Also, we can user our custom data provider classes these implement "RowMapperObjectFieldDataProvider" interface with its "public Object provideData(T ownerObj)" method. Here is sample usage:

public class User {

    ...

    @RowMapperObjectField(
        provideViaCustomProvider = 
            @RowMapperCustomProvider(
                dataProvider = MyCustomDataProvider.class), 
        lazy = true)
    private List<Role> roles = new ArrayList<Role>();

    ...

}

You can find all demo codes (including these samples above) at https://github.com/serkan-ozal/spring-jdbc-roma-demo

Roadmap

SQL based provider will be supported for getting relations with pure SQL queries by specifying datasource as follows:

public class User {

    ...

    @RowMapperObjectField(
        provideViaSqlProvider = 
            @RowMapperSqlProvider(
                sql = 
                    "SELECT r.* FROM ROLE r WHERE r.ID IN " +
                    "(" +
                        "SELECT ur.ROLE_ID FROM user_role ur WHERE ur.USER_ID = ${id}" +
                    ") ORDER BY r.name",
                dataSource = "MyDataSource"),
        lazy = true)
    private List<Role> roles = new ArrayList<Role>();

    ...

}

Field based formatters will be supported for formating field from raw value by impelenting custom formatter classes from "RowMapperFieldGeneratorFormatter" interface and overriding "public T format(T value)" method. Here is sample usage:

public class User {

    ...

    @RowMapperField(
        columnName = "surname", 
        fieldFormatters = {MyTrimFormatter.class, MyUpperCaseFormatter.class})
    private String surname;

    ...

}