Refactored the parsing of 'pandas_categorical' attribute

NOTICE.txt

@@ -1,4 +1,5 @@
 JPMML-LightGBM includes third-party dependencies that are released under the Apache License, Version 2.0:
+  * Gson - https://github.com/google/gson
   * Guava - https://github.com/google/guava
   * JCommander - http://jcommander.org
 

pmml-lightgbm/pom.xml

@@ -39,6 +39,11 @@
 			<scope>provided</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>com.google.code.gson</groupId>
+			<artifactId>gson</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>
@@ -65,28 +70,8 @@
 				<artifactId>maven-javadoc-plugin</artifactId>
 				<configuration>
 					<javadocVersion>1.8</javadocVersion>
-					<sourcepath>${basedir}/src/main/java</sourcepath>
 				</configuration>
 			</plugin>
-			<plugin>
-				<groupId>org.codehaus.mojo</groupId>
-				<artifactId>javacc-maven-plugin</artifactId>
-				<version>3.0.1</version>
-				<executions>
-					<execution>
-						<goals>
-							<goal>javacc</goal>
-						</goals>
-					</execution>
-				</executions>
-				<dependencies>
-					<dependency>
-						<groupId>net.java.dev.javacc</groupId>
-						<artifactId>javacc</artifactId>
-						<version>7.0.13</version>
-					</dependency>
-				</dependencies>
-			</plugin>
 		</plugins>
 	</build>
 </project>

pmml-lightgbm/src/main/java/org/jpmml/lightgbm/GBDT.java

@@ -68,7 +68,7 @@ public class GBDT {
 
 	private Map<String, String> feature_importances = Collections.emptyMap();
 
-	private List<List<Object>> pandas_categorical = Collections.emptyList();
+	private List<List<?>> pandas_categorical = Collections.emptyList();
 
 
 	public void load(List<Section> sections){
@@ -611,7 +611,7 @@ private Map<String, String> loadFeatureSection(Section section){
 		return result;
 	}
 
-	private List<List<Object>> loadPandasCategorical(Section section){
+	private List<List<?>> loadPandasCategorical(Section section){
 		String id = section.id();
 
 		try {

pmml-lightgbm/src/main/java/org/jpmml/lightgbm/PandasCategoricalParser.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2023 Villu Ruusmann
+ *
+ * This file is part of JPMML-LightGBM
+ *
+ * JPMML-LightGBM is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * JPMML-LightGBM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with JPMML-LightGBM.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.jpmml.lightgbm;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParser;
+import com.google.gson.ToNumberPolicy;
+
+public class PandasCategoricalParser {
+
+	private String string = null;
+
+
+	public PandasCategoricalParser(String string){
+		setString(string);
+	}
+
+	public List<List<?>> parsePandasCategorical(){
+		String string = getString();
+
+		if(!string.startsWith(PandasCategoricalParser.PREFIX)){
+			throw new IllegalArgumentException(string);
+		}
+
+		string = string.substring(PandasCategoricalParser.PREFIX.length());
+
+		JsonElement element = JsonParser.parseString(string);
+
+		Gson gson = new GsonBuilder()
+		    .setObjectToNumberStrategy(ToNumberPolicy.LONG_OR_DOUBLE)
+		    .create();
+
+		List<List<?>> result = gson.fromJson(element, ListOfLists.class);
+		if(result == null){
+			result = Collections.emptyList();
+		}
+
+		return result;
+	}
+
+	public String getString(){
+		return this.string;
+	}
+
+	private void setString(String string){
+		this.string = string;
+	}
+
+	static
+	private class ListOfLists extends ArrayList<List<?>> {
+	}
+
+	private static final String PREFIX = "pandas_categorical:";
+}

pmml-lightgbm/src/test/java/org/jpmml/lightgbm/PandasCategoricalParserTest.java

@@ -22,8 +22,6 @@
 import java.util.Collections;
 import java.util.List;
 
-import org.jpmml.lightgbm.PandasCategoricalParser;
-import org.jpmml.lightgbm.ParseException;
 import org.junit.Test;
 
 import static org.junit.Assert.assertEquals;
@@ -32,17 +30,17 @@ public class PandasCategoricalParserTest {
 
 	@Test
 	public void parse() throws Exception {
-		List<List<Object>> pandasCategories = parsePandasCategorical("null");
+		List<List<?>> pandasCategories = parsePandasCategorical("null");
 
 		assertEquals(Collections.emptyList(), pandasCategories);
 
 		pandasCategories = parsePandasCategorical("[[\"null\", \"A\", \"B, B\", \"C, [C], C\"], [-2, -1, 0, 1, 2], [-2.0, -1.0, 0.0, 1.0, 2.0], [false, true]]");
 
-		assertEquals(Arrays.asList(Arrays.asList("null", "A", "B, B", "C, [C], C"), Arrays.asList(-2, -1, 0, 1, 2), Arrays.asList(-2d, -1d, 0d, 1d, 2d), Arrays.asList(Boolean.FALSE, Boolean.TRUE)), pandasCategories);
+		assertEquals(Arrays.asList(Arrays.asList("null", "A", "B, B", "C, [C], C"), Arrays.asList(-2L, -1L, 0L, 1L, 2L), Arrays.asList(-2d, -1d, 0d, 1d, 2d), Arrays.asList(Boolean.FALSE, Boolean.TRUE)), pandasCategories);
 	}
 
 	static
-	private List<List<Object>> parsePandasCategorical(String value) throws ParseException {
+	private List<List<?>> parsePandasCategorical(String value){
 		PandasCategoricalParser parser = new PandasCategoricalParser("pandas_categorical:" + value);
 
 		return parser.parsePandasCategorical();

pom.xml

@@ -84,6 +84,12 @@
 				<version>1.72</version>
 			</dependency>
 
+			<dependency>
+				<groupId>com.google.code.gson</groupId>
+				<artifactId>gson</artifactId>
+				<version>[2.8.1, 2.10.1]</version>
+			</dependency>
+
 			<dependency>
 				<groupId>junit</groupId>
 				<artifactId>junit</artifactId>