apache Empire-db
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| Developer(s) | Apache Software Foundation |
|---|---|
| Written in | Java |
| Operating system | Cross-platform |
| Type | Persistence Framework |
| License | Apache License 2.0 |
| Website | http://incubator.apache.org/empire-db |
Apache Empire-db is an Java component that provides a high level object oriented API for accessing Relational database management systems (RDBMS) through JDBC. Apache Empire-db is Open Source and provided under the Apache 2.0 license from the Apache Software Foundation.
Compared to Object-relational mapping (ORM) or other data persistence solutions such as Hibernate, iBATIS or TopLink Empire-db does not use XML files or Java annotations to provide a mapping of plain (old) java object (POJO's) to database tables, views and columns. Instead Empire-db uses a Java object model to describe the underlying data model and an API that works with object references rather than string literals.
Empire-db's aim is to provide better software quality and improved maintainability through increased compile-time safety and reduced redundancies of metadata.
Major benefits
Empire-db’s key strength is its API for dynamic SQL generation for arbitrary select, update, insert or delete statements, purely by using Java methods which reference the model objects. This provides type-safety and entirely eliminates the use of string literals for names or expressions in code. Additionally DBMS independence is achieved through a pluggable driver model.
Using references to table and column objects significantly improves compile-time safety and thus reduces the amount of testing. As a positive side effect the IDE’s code completion can be used to browse the data model, increases productivity and eliminates the need for other external tools or IDE-plugins.
Further the object model also provides safe and easy access to meta-information of the data model such as field data type, maximum field length, whether a field is mandatory and a finite choice of options for a field’s values. Metadata is user-extensible and not limited to DBMS related metadata. Availability of meta-information encourages more generic code and eliminates redundancies throughout application layers.
Features at a glance
- RDBMS independent data model definition in Java requires no XML schemas or annotations to learn and easily allows user defined interceptions and extensions.
- Portable record handling and command definition with support for a variety of relational databases such as Oracle, Microsoft SQL-Server, MySQL, Derby, H2 and HSQLDB (as of version 2.0.5)
- DDL generation for target DBMS from object definition, either for the entire database or for individual objects such as tables, views, columns and relations.
- Type-safe API for dynamic SQL command generation allows dynamic building of SQL statements using API methods and object references only instead of string literals. This provides a high degree of type-safety which simplifies testing and maintenance.
- Reduced amount of Java code and powerful interception of field and metadata access through dynamic beans as an alternative to POJO’s. This even supports data model changes (DDL) at runtime.
- Automatic tracking of record state and field modification (aka "dirty checking") to only insert/ update modified fields.
- Support for optimistic locking through timestamp column.
- No need to always work with full database entities. Build queries to provide you with the data exactly as you need it, and obtain the result for example as a list of any type of POJO with matching property setters or constructor.
- Lightweight and passive library with zero configuration footprint that allows simple integration with any architecture or framework.
Example
Consider a database with two tables called Employees and Departments for which a list of Employees in a particular format, with certain constraints and a given order should be retrieved. The corresponding Oracle syntax SQL statement might be as follows:
SELECT t1.EMPLOYEE_ID,
t1.LASTNAME || ', ' || t1.FIRSTNAME AS NAME,
t2.DEPARTMENT
FROM (EMPLOYEES t1 INNER JOIN DEPARTMENTS t2
ON t1.DEPARTMENT_ID = t2.DEPARTMENT_ID)
WHERE upper(t1.LASTNAME) LIKE upper('Foo%')
AND t1.RETIRED=0
ORDER BY t1.LASTNAME, t1.FIRSTNAME
This statement can be created using Empire-db's command API provided as follows:
SampleDB db = getDatabase();
// Declare shortcuts (not necessary but convenient)
SampleDB.Employees EMP = db.EMPLOYEES;
SampleDB.Departments DEP = db.DEPARTMENTS;
// Create a command object
DBCommand cmd = db.createCommand();
// Select columns
cmd.select(EMP.EMPLOYEE_ID);
cmd.select(EMP.LASTNAME.append(", ").append(EMP.FIRSTNAME).as("NAME"));
cmd.select(DEP.DEPARTMENT);
// Join tables
cmd.join (EMP.DEPARTMENT_ID, DEP.DEPARTMENT_ID);
// Set constraints
cmd.where(EMP.LASTNAME.likeUpper("Foo%"));
cmd.where(EMP.RETIRED.is(false));
// Set order
cmd.orderBy(EMP.LASTNAME);
cmd.orderBy(EMP.FIRSTNAME);
The result of this query can be easily retrieved as a list of POJO's objects like this:
public class EmployeeInfo {
private int employeeId;
private String name;
private String department;
// Gettter's and Setters for all properties
// or a public Constructor using fields
public get...
public set...
}
// Retrieve Employee list using the cmd object created above
DBReader reader = new DBReader();
reader.open(cmd, getConnection());
List<EmployeeInfo> empList = reader.getBeanList(EmployeeInfo.class);
Empire-db also supports field access thorugh object references or obtaining query results as XML.
History
Empire-db was originally developed at ESTEAM Software a German software company which used Empire-db to develop various applications for a variety of branches.
In January 2008 Empire-db was made officially Open Source and first published though SourceForge.Net. In June 2008 a proposal was submitted to the Apache Software Foundation for Empire-db to become an Apache Incubator project. In July 2008 Empire-db got accepted for incubation and all rights over the Software were transferred to the Apache Foundation.
In October 2008 Empire-db 2.0.4 was the first official Apache release with all package names changed to begin with org.apache.empire.
