Fix exception when parsing empty values in DefaultJobParametersConverter

Resolves #4505

Author: fmbenhassine

spring-batch-core/src/main/java/org/springframework/batch/core/converter/DefaultJobParametersConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -169,7 +169,11 @@ protected JobParameter<?> decode(String encodedJobParameter) {
 	}
 
 	private String parseValue(String encodedJobParameter) {
-		return StringUtils.commaDelimitedListToStringArray(encodedJobParameter)[0];
+		String[] tokens = StringUtils.commaDelimitedListToStringArray(encodedJobParameter);
+		if (tokens.length == 0) {
+			return "";
+		}
+		return tokens[0];
 	}
 
 	private Class<?> parseType(String encodedJobParameter) {

spring-batch-core/src/test/java/org/springframework/batch/core/converter/DefaultJobParametersConverterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,7 @@
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.batch.core.JobParameter;
 import org.springframework.batch.core.JobParameters;
 import org.springframework.batch.core.JobParametersBuilder;
 import org.springframework.util.StringUtils;
@@ -129,6 +130,22 @@ void testGetParametersWithBogusLong() {
 		}
 	}
 
+	@Test
+	void testGetParametersWithEmptyValue() {
+		// given
+		String[] args = new String[] { "parameter=" };
+
+		// when
+		JobParameters jobParameters = factory.getJobParameters(StringUtils.splitArrayElementsIntoProperties(args, "="));
+
+		// then
+		assertEquals(1, jobParameters.getParameters().size());
+		JobParameter<?> parameter = jobParameters.getParameters().get("parameter");
+		assertEquals("", parameter.getValue());
+		assertEquals(String.class, parameter.getType());
+		assertTrue(parameter.isIdentifying());
+	}
+
 	@Test
 	void testGetParametersWithDoubleValueDeclaredAsLong() {