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HOWTO.md

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Overview

In this document, we're going to focus on how to encode and decode OpenLR locations on digital maps using modules in this package.

SetUp

We'll need to add the following dependencies to our pom.xml

Note: Replace ${openlr.version} with the version of the library you wish to use.

<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>encoder</artifactId>
 <version>${openlr.version}</version>
</dependency>
<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>decoder</artifactId>
 <version>${openlr.version}</version>
</dependency>
<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>map</artifactId>
 <version>${openlr.version}</version>
</dependency>
<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>data</artifactId>
 <version>${openlr.version}</version>
</dependency>
<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>binary</artifactId>
 <version>${openlr.version}</version>
</dependency>
<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>xml</artifactId>
 <version>${openlr.version}</version>
</dependency>
<dependency>
 <groupId>org.openlr</groupId>
 <artifactId>proto</artifactId>
 <version>${openlr.version}</version>
</dependency>

Map Implementation

Implement the following interfaces against the map you want to use

  • openlr.map.Line
  • openlr.map.Node
  • openlr.map.MapDatabase

Load Map

We are using the sqlite database for the remaining part of the document 

MapLoadParameter param = new DBFileNameParameter();
param.setValue("path/to/map");
OpenLRMapLoader loader = new SQLiteMapLoader();
MapDatabase map = loader.load(Arrays.asList(param));

Physical Format

Choose the physical format of the OpenLR location reference container
The following three formats are available in this package:

  • binary: openlr.binary
  • protobuf: openlr.proto
  • xml: openlr.xml

We are choosing binary format for the remaining part of the document

Encoder

The code snippet given below shows how to encode a line location on the map in OpenLR binary format.

you can find the default encoder properties file in openlr/encoder/src/main/resources/OpenLR-Encoder-Properties.xml

In the example given below we are encoding a line location with connected lines (1,2,3,4)

//Build the line location
List<Line>  testLocation = Arrays.asList(mapDatabaseAdapter.getLine(1),
                                         mapDatabaseAdapter.getLine(2),
                                         mapDatabaseAdapter.getLine(3),
                                         mapDatabaseAdapter.getLine(4));
Location location = LocationFactory.createLineLocation("Test location", testLocation, 0, 0);

//Initialize the physical format encoder
PhysicalEncoder physicalEncoder = new OpenLRBinaryEncoder();

//Build the encoder configurations
Configuration encoderConfig = OpenLRPropertiesReader.loadPropertiesFromFile(new File("OpenLR-Encoder-Properties.xml"));
OpenLREncoderParameter params = new OpenLREncoderParameter.Builder().with(map).with(encoderConfig)
                .with(Arrays.asList(physicalEncoder))
                .buildParameter();

//Initialize the onpenlr encoder
OpenLREncoder encoder = new openlr.encoder.OpenLREncoder();

//Encode the line location in openlr format
LocationReferenceHolder locationReferenceHolder = encoder.encodeLocation(params, location);

//Generate the binary for the openlr location referencing container
String locationReferenceBinary = ((ByteArray) physicalEncoder.encodeData(locationReferenceHolder.getRawLocationReferenceData()).getLocationReferenceData()).getBase64Data();

Decoder

The code snippet given below shows how to decode an OpenLR binary location reference on to a map.

you can find the default encoder properties file in openlr/decoder/src/main/resources/OpenLR-Decoder-Properties.xml

In the example given below we are decoding OpenLR location reference binary string

//base64 openlr binary string  to decode 
String openlr = "CwmQ9SVWJS2qBAD9/14tCQ==";

//Initialize the binary decoder and decode the binary string
OpenLRBinaryDecoder binaryDecoder = new OpenLRBinaryDecoder();
ByteArray byteArray = new ByteArray(Base64.getDecoder().decode(openlr));
LocationReferenceBinaryImpl locationReferenceBinary = new LocationReferenceBinaryImpl("Test location", byteArray);
RawLocationReference rawLocationReference = binaryDecoder.decodeData(locationReferenceBinary);

//Build the decoder configuration
Configuration decoderConfig = OpenLRPropertiesReader.loadPropertiesFromFile(new File(TestMapStubTest.class.getClassLoader().getResource("OpenLR-Decoder-Properties.xml").getFile()));
OpenLRDecoderParameter params = new OpenLRDecoderParameter.Builder().with(map).with(decoderConfig).buildParameter();

//Initialize the decoder
OpenLRDecoder decoder = new openlr.decoder.OpenLRDecoder();

//decode the location
Location location = decoder.decodeRaw(params, rawLocationReference);