FilterLib

Filtering library which extends JPA 2 query posibilities, in similar way as Hibernates Query By Example.

About

FilterLib provides different somewhat more declarative approach for querying database data. Simple POJOs serves as basic query objects. These pojos are parsed by this library and field values together with optional annotations are used to construct DB queries using JPA Criteria API. This apporach can be seen as filtering database tables using prearanged filters. (Later should be provided also way for projections and construction of new objects from these results). It's also similar to Hibernates Query By Example mechanism.

How to use it

Main function of this library is provided by abstract class org.obozek.filterlib.AbstractFilteringRepository and its filter() method. So you have to provide some subclass extending this abstract class. To get you started quickly there is one suitable implementation of Generic dao - org.obozek.filterlib.dao.GenericDaoImpl which extends AbstractFilteringRepository. This small library is also used in few projects together with Spring Data. So it should integrate well with this framework. (Instructions will be provided later)

So lets start with simple example which will outline basic usage of this library. Lets have table called Customer. This table has few attributes and also two one-to-many associations to Payment and Order tables. See below:

+---------------------+         +-------------------------------+           +------------------------+
|       Payment       |         |           Customer            |           |         Order          |
+---------------------+         +-------------------------------+           +------------------------+
|PaymentPK paymentPK; |         |Integer customerNumber;        |           |Integer orderNumber;    |
|Date paymentDate;    |0------->|String customerName;           |<---------0|Date orderDate;         |
|Double amount;       |         |String contactLastname;        |           |Date requiredDate;      |
|Customer customer;   |         |String contactFirstname;       |           |Date shippedDate;       |
+---------------------+         |String phone;                  |           |String status;          |
                                |String addressLine1;           |           |String comments;        |
                                |String addressLine2;           |           |Customer customerNumber;|     
                                |String city;                   |           +------------------------+
                                |String state;                  |           
                                |String postalCode;             |
                                |String country;                |
                                |Integer salesrepEmployeeNumber;|
                                |Double creditLimit;            |
                                |List<Payment> paymentList;     |
                                |List<Order> orderList;         |
                                +-------------------------------+

Corresponding entity classes are located in test directory in package org.obozek.filterlib.test.entities.

Lets say we want to query Customer entities by customerNumber. All we need to have is some kind of POJO object which contains field named cutomerNumeber of comparable type. All the other fields present in this POJO filter have to be null(or annotated with special annotation more later). Otherwise the they would be also processed by FilterLib. So we can eg use empty Customer object with only customerNumber field filled, or we can create special filtering object just for querying our Customer entities. Then simply