NullPointerException while using MongoTemplate in Spring boot - mongodb

Question

I have a collection named 'statusbynumbers' and I define the entity like this:
#Document(collection="statusbynumbers")
#Data
#AllArgsConstructor
#NoArgsConstructor
public class StatusByNumbersEntity {
#Id
private String id;
#Field("number")
private String number;
#Field("level")
private String
#Field("yat")
private double yat;
}
the key 'yat' is a double type in the db. But in my business logic, in some cases, 'yat' can be null. Then when I uses MongoTemplate.find() method, java.lang.NullPointerException: null was caused. The MongoTemplate.find() used in my code shown as below:
public class ReportsServiceImpl implements ReportsService {
#Resource
private MongoTemplate ReportsMongoTemplate;
#Override
public List<StatusByNumbersEntity> getNumbersByFilterLevel(String filterLevel) {
List<Integer> filterLevelList = FilterLevelModel.buildFilterLevel(filterLevel);
Criteria criteria = Criteria.where("level").in(filterLevelList);
Query query = new Query(criteria);
// java.lang.NullPointerException: null caused by the following code
List<StatusByNumbersEntity> numList = ReportsMongoTemplate.find(query,StatusByNumbersEntity.class);
...
}
The detailed error log shown as below
2017-10-10 02:47:06.475 ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is
java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
at sun.invoke.util.ValueConversions.unboxDouble(ValueConversions.java:139)
at com.test.application.entities.reports.numbersEntity_Accessor_22t0xt.setProperty(Unknown Source)
at org.springframework.data.mapping.model.ConvertingPropertyAccessor.setProperty(ConvertingPropertyAccessor.java:58)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:291)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter$1.doWithPersistentProperty(MappingMongoConverter.java:279)
at org.springframework.data.mapping.model.BasicPersistentEntity.doWithProperties(BasicPersistentEntity.java:330)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:279)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:239)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:199)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:195)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:85)
at org.springframework.data.mongodb.core.MongoTemplate$ReadDbObjectCallback.doWith(MongoTemplate.java:2324)
at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:1969)
at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1787)
at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1770)
at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:644)
at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:635)
How can i use the MongoTemplate.find() method even if the key "yat" can be null instead of double type to avoid this NullPointerException?

Answer 1

It's because you used a primitive type variable(double with lowercase 'd') for a nullable field.
You can't set null value for primitive data types(trows NullPointerException)
Replace 'double' with 'Double'
#Field("yat")
private Double yat;
Remember that you can't cast a null value to primitive data types either.
for when you had setters and getters replace the primitive type with non-primitive equivalent in them as well.
more details:
https://www.w3schools.com/java/java_data_types.asp