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Bindaas Modifiers

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Pradeeban Kathiravelu edited this page Aug 24, 2018 · 3 revisions

Overview

Bindaas Framework has a pluggable architecture that provides variety of interfaces for various classes of applications. Bindaas can be easily extended and customized by implementing these interfaces. In this article we shall learn how to write applications using the Modifier interface. There are three different types of Modifiers that Bindaas provides :

  1. Query Modifier (QM)
  2. Query Result Modifier (QRM)
  3. Submit Payload Modifier (SPM)

QM is associated with the Query Execution workflow. When a RESTful request is fired,HTTP GET, right before delegating control to a QueryHandler, the raw query is passed through a series of Query Modifiers, if declared by the Query Author at the time of creating the query API. These QMs are intended to "change" the query is some meaningful way before passing it downstream. A classic use-case of a QM would be performing access-control by looking at the query and the privileges of the user who invoked this API.

QRM is also associated with the Query Execution workflow, but instead of acting on the query it acts on the results of query execution. It is intended to augment or modify the results in some meaningful way before writing it over the wire. For example, the Image Download QRM written for the TCIA API use-case processes raw JSON produced by the upstream QueryHandler, looks-up physical filepaths of the images and packages them in a zip file while streaming it over the network. 

SPM is associated with the Submit API Execution workflow. Right before the data BLOB produced as a result of HTTP POST request is supplied to a Submit Handler, it is passed through a SPM, which is suppose to modify/preprocess it in some meaningful way. SPM could be used to process DICOM images, extract relevant DICOM tags and pass it on to the downstream database for storage. 

The source code for sample modifiers that are referenced in this section can be found in the Bindaas repository at : source/projects/demos/LoggingModifiers

 

IModifier Interface 

public interface IModifier {
    public JsonObject getDocumentation(); // documentation pertaining the Modifier (optional)
    public void validate() throws ModifierException; // any validation that needs to performed (optional)
    public String getDescriptiveName(); // descriptive name of the Modifier plugin. Used in the webconsole to identify this plugin (required)
}

IQueryModifier Interface 

public interface IQueryModifier extends IModifier {
    public String modifyQuery(String query , JsonObject dataSource , RequestContext requestContext, JsonObject modifierProperties) throws AbstractHttpCodeException;
    public Map<String,String> modiftQueryParameters(Map<String,String> queryParams , JsonObject dataSource , RequestContext requestContext , JsonObject modifierProperties) throws AbstractHttpCodeException;
}

String query : Query passed on to the QM before it passes to QueryHandler

JsonObject dataSource : Configuration object hosting values specified at the time of creating an instance of Data Provider

RequestContext requestContext : Context object representing the state of the request. Contains information about the user who invoked this API

JsonObject modifierProperties : Properties required to configure this QM

Map<String,String> queryParams : Runtime query parameters provided by the user

The method returns the query modified by the plugin.

IQueryResultModifier interface 

public interface IQueryResultModifier extends IModifier {
public QueryResult modifyQueryResult(QueryResult queryResult ,  JsonObject dataSource , RequestContext requestContext , JsonObject modifierProperties , Map<String,String> queryParams) throws AbstractHttpCodeException;
}

QueryResult queryResult : QueryResult object resulting from the query API execution

JsonObject dataSource : Configuration object hosting values specified at the time of creating an instance of Data Provider

RequestContext requestContext : Context object representing the state of the request. Contains information about the user who invoked this API

JsonObject modifierProperties : Properties required to configure this QRM

Map<String,String> queryParams : Query parameters provided with the URL

The method returns the modified QueryResult object.

ISubmitPayloadModifier interface 

public interface ISubmitPayloadModifier extends IModifier {
    public  InputStream transformPayload( InputStream data , SubmitEndpoint submitEndpoint , JsonObject modifierProperties, RequestContext requestContext) throws AbstractHttpCodeException;
    public  String transformPayload( String data , SubmitEndpoint submitEndpoint , JsonObject modifierProperties , RequestContext requestContext) throws AbstractHttpCodeException;
}

InputStream/String data : data to be processed by the SubmitHandler

SubmitEndpoint submitEndpoint : The instance of submitEndpoint associated with the request

RequestContext requestContext : Context object representing the state of the request. Contains information about the user who invoked this API

JsonObject modifierProperties : Properties required to configure this QRM

The method returns the modified data object.

More Information

Writing a Query Modifier

Writing a Query Result Modifier

Writing a Payload Modifier

Testing and distributing modifiers

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