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ORM Artifacts

Integration of WaveMaker app with database generates few files, services, and APIs. These are used internally by WaveMaker to achieve the seamless integration. This information is for advanced developers who want more control or need more information for academic interests.

Layered Architecture

When a database is integrated into a WaveMaker app, it generates the source code for CRUD operations for each entity within the database. In addition to the CRUD APIs, the filter, count, and export APIs are also generated. Associated APIs in the case of related tables are also generated.

The source code is generated with the ORM, Service Layer & REST APIs with each layer having a specific responsibility:

  • Layer 1: REST Controller is responsible for transporting the data between client and server, authorization of APIs & marshaling and unmarshaling of the model to JSON etc.
  • Layer 2: Service Layer is responsible for validating the inputs and transaction management
  • Layer 3: DAO Layer is responsible for interacting with the underlying database

The following diagram depicts the Layered Architecture mentioned above:

Generated Files

The folder structure for the generated code is as follows:

  1. Controllers generated for entities (one for each entity), queries and procedures:

  1. Data Access Objects (DAO) for each of the entities:

  1. Service Interfaces and Service Implementations for entities, queries, and procedures

  1. POJOs for each entity

Each of the layers performs its function and delegates the call to the next layer in the chain. For example, after the unmarshaling of the JSON data to the model, and authorization checks, the REST layer delegates the call to the service layer, and more.

Design time Configuration Files

It contains files required for designing database.

  • db-connection-settings.json: it contains connection properties.
  • servicename_API.json: Generated API specification (swagger) of given service.
  • servicename_procedure.json: contains information regarding procedures for that service.
  • servicename_query.json: contains information regarding query for that service.
  • servicename_published_datamodel.json: contains database schema information. It plays a major role while updating DB changes. Whenever you do manual changes in the database you have to re-import to update this file.
  • servicename_draft_datamodel.json: Contains user modifications. It’ll delete when we do update/re-import database.
  • servicedef.xml: contains types information for this service.

Generated APIs for Database Services

Import or creation of database within a WaveMaker app results in the auto-generation of ORM artifacts from the Database Schema and as such each Schema needs to have a Primary key either single or composite.

In case your external database schema comes without a primary key, you need to assign a column(s) as virtual primary key else all the columns are treated as part of a composite primary key. For each entity imported, a REST API is generated for each of the CRUD operations, Filter and Count functionalities. These REST APIs are exposed via the API Designer and can be tested and reconfigured as per the application needs.

As an example, we are using the following Employee-Department Database Schema (Sample hrdb that can be imported into Studio) with a unique constraint for Dept_code on the department table:

Request Mapping:

[PROJECT_ID]/[PROJECT_NAME]/services/[SERVICE_NAME]/[ENTITY_NAME]/

Example:

CRUD APIs

Create

Inserts a record into the table.

  • URL: /
  • Request Type: POST
  • Path Variables: None
  • Request Parameter: None
  • Request Body: object in JSON format
  • Method Name Example: createEmployee

Read (primary key based)

Retrieves the data associated with given ID value.

  • URL: /{id}
  • Request Type: GET
  • Path Variables: primary key column value
  • Request Parameter: None
  • Request Body: none
  • Method Name Example: getEmployee

Read (unique key based)

Retrieves the data associated with given unique key value.

  • URL: /[UNIQUE_KEY]/{unique_key_value}
  • Request Type: GET
  • Path Variables: unique key column value
  • Request Parameter: None
  • Request Body: none
  • Method Name Example: getByDeptCode (unique key for department entity)

Read (foreign key based)

Retrieves the data associated with given ID value from the related table.

  • URL: /{id..+}/[relation_field]
  • Request Type: GET
  • Path Variables: primary key column value
  • Request Parameter:
    • Page,
    • Size,
    • Sort
  • Request Body: none
  • Method Name: findAssociatedEmployees (employee foreign key for department entity)

READ (foreign key based - self-referential)

Retrieves the data associated with given ID value

  • URL: /{id..+}/[relation_field]
  • Request Type: GET
  • Path Variables: primary key column value
  • Request Parameter:
    • Page,
    • Size,
    • Sort
  • Request Body: none
  • Method Name: findAssociatedEmployeesForManagerId (foreign key)

Update

Updates entity record associated with the given id value

  • URL: /{id}
  • Request Type: PUT
  • Request Type: primary key column value
  • Request Parameter: None
  • Request Body: object in JSON format
  • Method Name Example: editEmployee

Delete

Deletes entity record associated with the given id.

  • URL: /{id}
  • Request Type: DELETE
  • Request Type: primary key column value
  • Request Parameter: None
  • Request Body: None
  • Method Name Example: deleteEmployee

Query APIs

note

Though the following APIs are available in POST and GET type, GET APIs might fail if the request URL is longer than 2048. It is advisable to use POST request type.

FILTER

Returns the list of entity instances matching the filter criteria (all values if query is not given).

  • URL: filter
  • Request Type: POST/GET
  • Request Type: None
  • Request Parameter:
    • custom query (optional, see here for query syntax),
    • Page,
    • Size,
    • Sort
  • Request Body: None Method Name: findEmployees

COUNT

Returns the count of filtered entity instances (total count if query not given)

  • URL: /count
  • Request Type: POST/GET
  • Request Type: None
  • Request Parameter: custom query (optional, see here for query syntax)
  • Request Body: None
  • Method Name: countEmployees

EXPORT

Returns the downloadable file url for the filtered data

  • URL: /export
  • Request Type: POST
  • Request Parameter: pageable - pagination and sorting options, see here for more,
    • Size,
    • Sort
  • Request Body: ExportOptions (Body)
    • custom query (optional, see here for query syntax),
    • fields list (optional):
    [{ “header”:”<column_display_name>”, “field”:”<entity_field_name>”, “expression”:”<custom_expression>” (eg: (${field_name} (or) <any string>)) }]
    • exportType - data format for export can be EXCEL or CSV
    • fileName: exported file name
  • Method Name Example: exportEmployees

Custom Query Syntax

The APIs generated by WaveMaker for all the imported tables will have methods that take a query as input. Here we will look at the usage of such query in APIs.

APIs that use HQL Queries: The Filter, Count and Export API in every Table Controller will use the HQL query, which is an optional parameter, for retrieving the data. These APIs can be found in respective tables’ controller class file.

Filter API

This API returns the list of Entity objects that matches the given filter conditions in the query. If query param is empty, API returns all the Entity objects.

Count API

Returns the count of Entities that matches the given filter conditions in the query. For an empty query, it returns the count of all Entity objects.

Export API

Returns a downloadable file with the list of Entities that matches the given filter conditions in the query. For an empty query, we get all the Entity objects.

Query Composition

The HQL query mainly consists of four types of parameters.

  • Field Name
  • Value Expression
  • Value
  • Logical Expression
note

Aggregate functions (avg(), sum(), min(), max()) in HQL query are currently not supported with these APIs.

FieldName parameter

  • The fieldName refers to the name of the field associated with the column in the respective table. The field name is derived from the column name in the table and usually camelCased.

  • The name of the field for a given column can be seen from DB Designer or the respectively generated model class. Field Name of a column can be found in DB designer on the selection of respective column in the properties panel.

  • Relational field names - In order to filter values with respect to an entity in relation, fieldname must be given as entityfield.fieldname. This is applicable only for ManyToOne and OneToOne Relations. Eg: department.name = ‘Engineering’, the name is the fieldname of Department.java

Value Expression parameter

Supported value expression types are listed in below table

OperationExpressionSupported Value TypesResultExamples
equals=Number or StringValues that equals to given value- empId=1
- firstname=’Eric’
not equals!=
(or)
< >		Number or StringValues that are not equal to given value- zip!=02127
- jobTitle< >‘Engineer’
betweenbetweenDate or NumberValues between given range
- birthdate between '1973-10-21' and '1986-06-18' (using date format - YYYY-MM-DD)
- zip between 14231 and 15922
less than<NumberValues less than given value- empId<6
greater than>NumberValues greater than given value- deptId>10
less than or equal to<=NumberValues less or equal to given value- empId<=4
greater than or equal to>=NumberValues greater than or equal to given value- zip>=11
pattern matchinglikeStringValues matching the given pattern- street like ‘4%Houston%’
starts withlikeStringValues starting with the given string- firstname like ‘E%’
ends withlikeStringValues ending with the given string- lastname like ‘%e’
containinglikeStringValues containing the given string- lastname like ‘%e%’
ininNumber or Date or StringValues in the given set- zip in (‘14231’, ‘02127’, ‘11212’)
- birthdate in ('1973-10-21' ,'1986-06-18')
- firstname in ( 'Sally' , 'William' , ‘Amanda’ )
nullis nullStringValues satisfying given condition- role is null
not nullis not nullStringValues satisfying given condition- date is not null
empty=StringValues satisfying given condition- lastname = ‘’
not empty!= (or) <>StringValues satisfying given condition- lastname <> ‘’
- lastname != ‘’

Value parameter

The “Value” parameter is the comparison value for the given field name. The value should be single quoted for non-numeric types. The format for the value of type date is ‘YYYY-MM-DD’.

Logical Expressions

  • A logical expression in HQL does one of the following:
    • joins two or more conditions to form a complex query
    • alters the logic of the conditions
  • Supported logical expressions with examples are listed below
  • Order of execution of conditions can be controlled using parenthesis. Eg: (empId=4 AND zip=02127 ) OR (city like 'New York%' OR birthdate between '1991-01-01' and '1999-12-31' )
Logical ExpressionResultsExamples
AND/andResult set satisfying both conditionsempId>5 AND firstname like ‘A%’
OR/orResult set satisfying either of the conditionsempId=5 OR deptId=1
NOT/notResult set satisfying negation of the conditionsNOT ( firstname like ‘A%’ AND empId=4)

For further reference to HQL query http://docs.jboss.org/hibernate/orm/4.3/manual/en-US/html/ch16.html

Last updated on 11/27/2019 by Swetha Kundaram
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