The Data Access Framework allows developers to retrieve different types of data without having dependencies on those types of data. It provides a single, unified data type that can be customized by individual implementing plug-ins to provide full functionality pertinent to each data type.
Writing a New Factory¶
Factories will most often be written in a dataplugin, but should always be written in a common plug-in. This will allow for clean dependencies from both CAVE and EDEX.
A new plug-in’s data access class must implement IDataFactory. For ease of use, abstract classes have been created to combine similar methods. Data factories do not have to implement both types of data (grid and geometry). They can if they choose, but if they choose not to, they should do the following:
throw new UnsupportedOutputTypeException(request.getDatatype(), "grid");
This lets the code know that grid type is not supported for this data factory. Depending on where the data is coming from, helpers have been written to make writing a new data type factory easier. For example, PluginDataObjects can use AbstractDataPluginFactory as a start and not have to create everything from scratch.
Each data type is allowed to implement retrieval in any manner that is felt necessary. The power of the framework means that the code retrieving data does not have to know anything of the underlying retrieval methods, only that it is getting data in a certain manner. To see some examples of ways to retrieve data, reference SatelliteGridFactory and RadarGridFactory.
Methods required for implementation:
public DataTime getAvailableTimes(IDataRequest request)
This method returns an array of DataTime objects corresponding to what times are available for the data being retrieved, based on the parameters and identifiers being passed in.
public DataTime getAvailableTimes(IDataRequest request, BinOffset binOffset)
This method returns available times as above, only with a bin offset applied.
Note: Both of the preceding methods can throw TimeAgnosticDataException exceptions if times do not apply to the data type.
public IGridData getGridData(IDataRequest request, DataTime…times)
This method returns IGridData objects (an array) based on the request and times to request for. There can be multiple times or a single time.
public IGridData getGridData(IDataRequest request, TimeRange range)
Similar to the preceding method, this returns IGridData objects based on a range of times.
public IGeometryData getGeometryData(IDataRequest request, DataTime times)
This method returns IGeometryData objects based on a request and times.
public IGeometryData getGeometryData(IDataRequest request, TimeRange range)
Like the preceding method, this method returns IGeometryData objects based on a range of times.
public String getAvailableLocationNames(IDataRequest request)
This method returns location names that match the request. If this does not apply to the data type, an IncompatibleRequestException should be thrown.
Registering the Factory with the Framework¶
The following needs to be added in a spring file in the plug-in that contains the new factory:
<bean id="radarGridFactory" class="com.raytheon.uf.common.dataplugin.radar.dataaccess.RadarGridFactory" /> <bean factory-bean="dataAccessRegistry" factorymethod="register"> <constructor-arg value="radar"/> <constructor-arg ref="radarGridFactory"/> </bean>
This takes the RadarGridFactory and registers it with the registry and allows it to be used any time the code makes a request for the data type “radar.”
Retrieving Data Using the Factory¶
For ease of use and more diverse use, there are multiple interfaces into the Data Access Layer. Currently, there is a Python implementation and a Java implementation, which have very similar method calls and work in a similar manner. Plug-ins that want to use the data access framework to retrieve data should include com.raytheon.uf.common.dataaccess as a Required Bundle in their MANIFEST.MF.
To retrieve data using the Python interface :
from awips.dataaccess import DataAccessLayer req = DataAccessLayer.newDataRequest() req.setDatatype("grid") req.setParameters("T") req.setLevels("2FHAG") req.addIdentifier("info.datasetId", "GFS40") times = DataAccessLayer.getAvailableTimes(req) data = DataAccessLayer.getGridData(req, times)
To retrieve data using the Java interface :
IDataRequest req = DataAccessLayer.newDataRequest(); req.setDatatype("grid"); req.setParameters("T"); req.setLevels("2FHAG"); req.addIdentifier("info.datasetId", "GFS40"); DataTime times = DataAccessLayer.getAvailableTimes(req) IData data = DataAccessLayer.getGridData(req, times);
This creates a new data request. Most often this is a DefaultDataRequest, but saves for future implentations as well.
This is the data type being retrieved. This can be found as the value that is registered when creating the new factory (See section above Registering the Factory with the Framework [radar in that case]).
This can differ depending on data type. It is most often used as a main difference between products.
This is often used to identify the same products on different mathematical angles, heights, levels, etc.
This differs based on data type, but is often used for more fine-tuned querying.
Both methods return a similar set of data and can be manipulated by their respective languages. See DataAccessLayer.py and DataAccessLayer.java for more methods that can be called to retrieve data and different parts of the data. Because each data type has different parameters, levels, and identifiers, it is best to see the actual data type for the available options. If it is undocumented, then the best way to identify what parameters are to be used is to reference the code.
In support of Hazard Services Raytheon Technical Services is building a generic data access framework that can be called via JAVA or Python. The data access framework code can be found within the AWIPS Baseline in
As of 2016, plugins have been written for grid, radar, satellite, Hydro (SHEF), point data (METAR, SYNOP, Profiler, ACARS, AIREP, PIREP), maps data, and other data types. The Factories for each can be found in the following packages (you may need to look at the development baseline to see these):
com.raytheon.uf.common.dataplugin.grid.dataaccess com.raytheon.uf.common.dataplugin.radar.dataaccess com.raytheon.uf.common.dataplugin.satellite.dataaccess com.raytheon.uf.common.dataplugin.binlightning.dataaccess com.raytheon.uf.common.dataplugin.sfc.dataaccess com.raytheon.uf.common.dataplugin.sfcobs.dataaccess com.raytheon.uf.common.dataplugin.acars.dataaccess com.raytheon.uf.common.dataplugin.ffmp.dataaccess com.raytheon.uf.common.dataplugin.bufrua.dataaccess com.raytheon.uf.common.dataplugin.profiler.dataaccess com.raytheon.uf.common.dataplugin.moddelsounding.dataaccess com.raytheon.uf.common.dataplugin.ldadmesonet.dataaccess com.raytheon.uf.common.dataplugin.binlightning.dataaccess com.raytheon.uf.common.dataplugin.gfe.dataaccess com.raytheon.uf.common.hydro.dataaccess com.raytheon.uf.common.pointdata.dataaccess com.raytheon.uf.common.dataplugin.maps.dataaccess
Additional data types may be added in the future. To determine what datatypes are supported display the “type hierarchy” associated with the classes
The following content was taken from the design review document which is attached and modified slightly.
The Data Access Framework is designed to provide a consistent interface for requesting and using geospatial data within CAVE or EDEX. Examples of geospatial data are grids, satellite, radar, metars, maps, river gage heights, FFMP basin data, airmets, etc. To allow for convenient use of geospatial data, the framework will support two types of requests: grids and geometries (points, polygons, etc). The framework will also hide implementation details of specific data types from users, making it easier to use data without worrying about how the data objects are structured or retrieved.
A suggested mapping of some current data types to one of the two supported data requests is listed below. This list is not definitive and can be expanded. If a developer can dream up an interpretation of the data in the other supported request type, that support can be added.
Map (states, counties, zones, etc)
Hydro DB (IHFS)
The framework is designed around the concept of each data type plugin contributing the necessary code for the framework to support its data. For example, the satellite plugin provides a factory class for interacting with the framework and registers itself as being compatible with the Data Access Framework. This concept is similar to how EDEX in AWIPS expects a plugin developer to provide a decoder class and record class and register them, but then automatically manages the rest of the ingest process including routing, storing, and alerting on new data. This style of plugin architecture effectively enables the framework to expand its capabilities to more data types without having to alter the framework code itself. This will enable software developers to incrementally add support for more data types as time allows, and allow the framework to expand to new data types as they become available.
The Data Access Framework will not break any existing functionality or APIs, and there are no plans to retrofit existing cosde to use the new API at this time. Ideally code will be retrofitted in the future to improve ease of maintainability. The plugin pecific code that hooks into the framework will make use of existing APIs such as IDataStore and IServerRequest to complete the requests.
The Data Access Framework can be understood as three parts:
How users of the framework retrieve and use the data
How plugin developers contribute support for new data types
How the framework works when it receives a request
How users of the framework retrieve and use the data¶
When a user of the framework wishes to request data, they must instantiate a request object and set some of the values on that request. Two request interfaces will be supported, for detailed methods see section “Detailed Code” below.
IGridRequest extends IDataRequest
IGeometryRequest extends IDataRequest
For the request interfaces, default implementations of DefaultGridRequest and DefaultGeometryRequest will be provided to handle most cases. However, the use of interfaces allows for custom special cases in the future. If necessary, the developer of a plugin can write their own custom request implementation to handle a special case.
After the request object has been prepared, the user will pass it to the Data Access Layer to receive a data object in return. See the “Detailed Code” section below for detailed methods of the Data Access Layer. The Data Access Layer will return one of two data interfaces.
IGridData extends IData
IGeometryData extends IData
For the data interfaces, the use of interfaces effectively hides the implementation details of specific data types from the user of the framework. For example, the user receives an IGridData and knows the data time, grid geometry, parameter, and level, but does not know that the data is actually a GFEGridData vs D2DGridData vs SatelliteGridData. This enables users of the framework to write generic code that can support multiple data types.
For python users of the framework, the interfaces will be very similar with a few key distinctions. Geometries will be represented by python geometries from the open source Shapely project. For grids, the python IGridData will have a method for requesting the raw data as a numpy array, and the Data Access Layer will have methods for requesting the latitude coordinates and the longitude coordinates of grids as numpy arrays. The python requests and data objects will be pure python and not JEP PyJObjects that wrap Java objects. A future goal of the Data Access Framework is to provide support to python local apps and therefore enable requests of data outside of CAVE and EDEX to go through the same familiar interfaces. This goal is out of scope for this project but by making the request and returned data objects pure python it will not be a huge undertaking to add this support in the future.
How plugin developers contribute support for new datatypes¶
When a developer wishes to add support for another data type to the framework, they must implement one or both of the factory interfaces within a common plugin. Two factory interfaces will be supported, for detailed methods see below.
IGridFactory extends IDataFactory
IGeometryFactory extends IDataFactory
For some data types, it may be desired to add support for both types of requests. For example, the developer of grid data may want to provide support for both grid requests and geometry requests. In this case the developer would write two separate classes where one implements IGridFactory and the other implements IGeometryFactory. Furthermore, factories could be stacked on top of one another by having factory implementations call into the Data Access Layer.
For example, a custom factory keyed to “derived” could be written for derived parameters, and the implementation of that factory may then call into the Data Access Layer to retrieve “grid” data. In this example the raw data would be retrieved through the GridDataFactory while the derived factory then applies the calculations before returning the data.
Implementations do not need to support all methods on the interfaces or all values on the request objects. For example, a developer writing the MapGeometryFactory does not need to support getAvailableTimes() because map data such as US counties is time agnostic. In this case the method should throw UnsupportedOperationException and the javadoc will indicate this.
Another example would be the developer writing ObsGeometryFactory can ignore the Level field of the IDataRequest as there are not different levels of metar data, it is all at the surface. It is up to the factory writer to determine which methods and fields to support and which to ignore, but the factory writer should always code the factory with the user requesting data in mind. If a user of the framework could reasonably expect certain behavior from the framework based on the request, the factory writer should implement support for that behavior.
Abstract factories will be provided and can be extended to reduce the amount of code a factory developer has to write to complete some common actions that will be used by multiple factories. The factory should be capable of working within either CAVE or EDEX, therefore all of its server specific actions (e.g. database queries) should go through the Request/Handler API by using IServerRequests. CAVE can then send the IServerRequests to EDEX with ThriftClient while EDEX can use the ServerRequestRouter to process the IServerRequests, making the code compatible regardless of which JVM it is running inside.
Once the factory code is written, it must be registered with the framework as an available factory. This will be done through spring xml in a common plugin, with the xml file inside the res/spring folder of the plugin. Registering the factory will identify the datatype name that must match what users would use as the datatype on the IDataRequest, e.g. the word “satellite”. Registering the factory also indicates to the framework what request types are supported, i.e. grid vs geometry or both.
An example of the spring xml for a satellite factory is provided below:
<bean id="satelliteFactory" class="com.raytheon.uf.common.dataplugin.satellite.SatelliteFactory" /> <bean id="satelliteFactoryRegistered" factory-bean="dataFactoryRegistry" factory-method="register"> <constructor-arg value="satellite" /> <constructor-arg value="com.raytheon.uf.common.dataaccess.grid.IGridRequest" /> <constructor-arg value="satelliteFactory" /> </bean>
How the framework works when it receives a request¶
IDataRequest requires a datatype to be set on every request. The framework will have a registry of existing factories for each data type (grid and geometry). When the Data Access Layer methods are called, it will first lookup in the registry for the factory that corresponds to the datatype on the IDataRequest. If no corresponding factory is found, it will throw an exception with a useful error message that indicates there is no current support for that datatype request. If a factory is found, it will delegate the processing of the request to the factory. The factory will receive the request and process it, returning the result back to the Data Access Layer which then returns it to the caller.
By going through the Data Access Layer, the user is able to retrieve the data and use it without understanding which factory was used, how the factory retrieved the data, or what implementation of data was returned. This effectively frees the framework and users of the framework from any dependencies on any particular data types. Since these dependencies are avoided, the specific IDataFactory and IData implementations can be altered in the future if necessary and the code making use of the framework will not need to be changed as long as the interfaces continue to be met.
Essentially, the Data Access Framework is a service that provides data in a consistent way, with the service capabilities being expanded by plugin developers who write support for more data types. Note that the framework itself is useless without plugins contributing and registering IDataFactories. Once the framework is coded, developers will need to be tasked to add the factories necessary to support the needed data types.
Requests and returned data interfaces will exist in both Java and Python. The Java interfaces are listed below and the Python interfaces will match the Java interfaces except where noted. Factories will only be written in Java.
void setDatatype(String datatype) - the datatype name and also the key to which factory will be used. Frequently pluginName such as radar, satellite, gfe, ffmp, etc
void addIdentifier(String key, Object value) - an identifier the factory can use to determine which data to return, e.g. for grib data key “modelName” and value “GFS40”
void setParameters(String… params)
void setLevels(Level… levels)
Levels will be represented as Strings
IGridRequest extends IDataRequest
void setStorageRequest(Request request) - a datastorage request that allows for slab, line, and point requests for faster performance and less data retrieval
No support for storage requests
IGeometryRequest extends IDataRequest
void setEnvelope(Envelope env) - a bounding box envelope to limit the data that is searched through and returned. Not all factories may support this.
setLocationNames(String… locationNames) - a convenience of requesting data by names such as ICAOs, airports, stationIDs, etc
Envelope methods will use a shapely.geometry.Polygon instead of Envelopes (shapely has no concept of envelopes and considers them as rectangular polygons)
Object getAttribute(String key) - getAttribute provides a way to get at attributes of the data that the interface does not provide, allowing the user to get more info about the data without adding dependencies on the specific data type plugin
DataTime getDataTime() - some data may return null (e.g. maps)
Level getLevel() - some data may return null
Levels will be represented by Strings
IGridData extends IData
Unit getUnit() - some data may return null
DataDestination populateData(DataDestination destination) - How the user gets the raw data by passing in a DataDestination such as FloatArrayWrapper or ByteBufferWrapper. This allows the user to specify the way the raw data of the grid should be structured in memory.
DataDestination populateData(DataDestination destination, Unit unit) - Same as the above method but also attempts to convert the raw data to the specified unit when populating the DataDestination.
Units will be represented by Strings
populateData() methods will not exist, instead there will be a getRawData() method that returns a numpy array in the native type of the data
IGeometryData extends IData
Set getParameters() - Gets the list of parameters included in this data
String getString(String param) - Gets the value of the parameter as a String
Number getNumber(String param) - Gets the value of the parameter as a Number
Unit getUnit(String param) - Gets the unit of the parameter, may be null
Type getType(String param) - Returns an enum of the raw type of the parameter, such as Float, Int, or String
String getLocationName() - Returns the location name of the piece of data, typically to correlate if the request was made with locationNames. May be null.
Geometry will be shapely.geometry.Geometry
getNumber() will return the python native number of the data
Units will be represented by Strings
getType() will return the python type object
DataAccessLayer (in implementation, these methods delegate processing to factories)
DataTime getAvailableTimes(IDataRequest request)
DataTime getAvailableTimes(IDataRequest request, BinOffset binOffset)
IData getData(IDataRequest request, DataTime… times)
IData getData(IDataRequest request, TimeRange timeRange)
GridGeometry2D getGridGeometry(IGridRequest request)
String getAvailableLocationNames(IGeometryRequest request)
No support for BinOffset
getGridGeometry(IGridRequest) will be replaced by getLatCoords(IGridRequest) and getLonCoords(IGridRequest) that will return numpy arrays of the lat or lon of every grid cell
Factory Interfaces (Java only)¶
DataTime getAvailableTimes(R request) - queries the database and returns the times that match the request. Some factories may not support this (e.g. maps).
DataTime getAvailableTimes(R request, BinOffset binOffset) - queries the database with a bin offset and returns the times that match the request. Some factories may not support this.
D getData(R request, DataTime… times) - Gets the data that matches the request at the specified times.
D getData(R request, TimeRange timeRange) - Gets the data that matches the request and is within the time range.
IGridDataFactory extends IDataFactory
GridGeometry2D getGeometry(IGridRequest request) - Returns the grid geometry of the data that matches the request BEFORE making the request. Useful for then making slab or line requests for subsets of the data. Does not support moving grids, but moving grids don’t make subset requests either.
IGeometryDataFactory extends IDataFactory
getAvailableLocationNames(IGeometryRequest request) - Convenience method to retrieve available location names that match a request. Not all factories may support this.