Java 17: InaccessibleObjectException due to illegal reflective access when saving entities containing a BigDecimal

I’m currently trying to migrate a project from Java 11 to Java 17 and I’m not able to get any code running when saving an entity containing a BigDecimal object in ElasticSearch. When trying to do so, I run into the following exception:

java.lang.reflect.InaccessibleObjectException: Unable to make field private final java.math.BigInteger java.math.BigDecimal.intVal accessible: module java.base does not "opens java.math" to unnamed module @2758fe70
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
	at java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:178)
	at java.base/java.lang.reflect.Field.setAccessible(Field.java:172)
	at org.springframework.util.ReflectionUtils.makeAccessible(ReflectionUtils.java:787)
	at org.springframework.data.mapping.context.AbstractMappingContext$PersistentPropertyCreator.doWith(AbstractMappingContext.java:520)
	at org.springframework.util.ReflectionUtils.doWithFields(ReflectionUtils.java:710)
	at org.springframework.data.mapping.context.AbstractMappingContext.doAddPersistentEntity(AbstractMappingContext.java:401)
	at org.springframework.data.mapping.context.AbstractMappingContext.addPersistentEntity(AbstractMappingContext.java:365)
	at java.base/java.util.Collections$SingletonSet.forEach(Collections.java:4905)
	at org.springframework.data.mapping.context.AbstractMappingContext$PersistentPropertyCreator.createAndRegisterProperty(AbstractMappingContext.java:568)
	at org.springframework.data.mapping.context.AbstractMappingContext$PersistentPropertyCreator.doWith(AbstractMappingContext.java:526)
	at org.springframework.util.ReflectionUtils.doWithFields(ReflectionUtils.java:710)
	at org.springframework.data.mapping.context.AbstractMappingContext.doAddPersistentEntity(AbstractMappingContext.java:401)
	at org.springframework.data.mapping.context.AbstractMappingContext.addPersistentEntity(AbstractMappingContext.java:365)
	at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:258)
	at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:201)
	at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:87)
	at org.springframework.data.mapping.context.MappingContext.getRequiredPersistentEntity(MappingContext.java:73)
	at org.springframework.data.elasticsearch.core.AbstractElasticsearchTemplate.getRequiredPersistentEntity(AbstractElasticsearchTemplate.java:646)
	at org.springframework.data.elasticsearch.core.AbstractElasticsearchTemplate.getIndexCoordinatesFor(AbstractElasticsearchTemplate.java:583)
	at org.springframework.data.elasticsearch.core.AbstractElasticsearchTemplate.save(AbstractElasticsearchTemplate.java:180)
	at com.redacted.ComponentTest.saveBigDecimal(ComponentTest.java:84)

I created two tests to check where the problem may lie. The Integer test succeeds, yet the BigDecimal test fails with the above exception.

@Test
  public void saveBigDecimal() {
    elasticsearchRestTemplate.save(new BigDecimalWrapper());
  }

  @Test
  public void saveInteger() {
    elasticsearchRestTemplate.save(new IntegerWrapper());
  }

  @Document(indexName = "bigDecimal-wrapper")
  static class BigDecimalWrapper{
    BigDecimal one = BigDecimal.ONE;
    BigDecimal ten = BigDecimal.TEN;
    String someString = "yeah";
  }

  @Document(indexName = "integer-wrapper")
  static class IntegerWrapper{
    Integer one = 1;
    int ten = 10;
    String someString = "yeah";
  }

To run this I am using Java 17 with SpringBoot 2.5.8 containing Spring Data ElasticSearch 4.2.7. I’m happy to provide more details if necessary, please let me know.

[sothawo]

You need to derive your configuration class from AbstractElasticsearchConfiguration like it’s shown in the documentation.

This not only creates the client but also initializes the internal objects like ElasticsearchMapper or the registered conversions. Spring Data Elasticsearch has some internal conversions built in, one is for converting BigDecimal to Double and back. (Elasticsearch does not support BigDecimal types, see https://www.elastic.co/guide/en/elasticsearch/reference/7.16/number.html).

So your configuration class would be (the second bean you had is provided by the base class already):

@Configuration
@EnableElasticsearchRepositories(basePackages = ["com.example"])
class ElasticsearchConfig(private val elasticsearchProperties: ElasticsearchProperties) : AbstractElasticsearchConfiguration() {
	@Bean
	override fun elasticsearchClient(): RestHighLevelClient {

		val clientConfiguration: ClientConfiguration = ClientConfiguration.builder()
			.connectedTo(elasticsearchProperties.url)
			.withBasicAuth(elasticsearchProperties.username, elasticsearchProperties.password)
			.build()
		return RestClients.create(clientConfiguration)
			.rest()
	}
}

Besides that, I’d recommend to add @Field annotations to your entity, so that when the application starts and the index is created, a correct mapping is written to the index; otherwise the type to use will be subject to Elasticsearch autodetection:

@Document(indexName = "testmodel")
data class TestModel(

	@Id
	val id: String,

	@Field(type = FieldType.Text)
	val test: String,

	@Field(type = FieldType.Double)
	val testValue: BigDecimal,
)

[ameltonyan]

I have the same problem and extending from AbstractElasticsearchConfiguration class solves the problem. Thanks a lot.