Problem of selector access with the JsonPropertyAccessor

Question

I encouter a problem while accessing a JsonNode with org.springframework.expression.spel.standard.SpelExpressionParser into a Spring Boot 2.2.4 service. I can describe the issue with the example below:

Given the Json as root object in a StandardEvaluationContext :

{"property":[{"name":"value1"},{"name":"value2"}]}

the spring expression language value with selector below returns value1 with no problem:

property.^[name != null].name

but this selector below returns null instead of value1:

property.^[name == 'value1'].name

any idea ?

EDIT:

here's a main method class example:

import java.util.List;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.integration.json.JsonPropertyAccessor;

public class TestJsonAccessor {

    public static void main(String[] args) throws JsonMappingException, JsonProcessingException {
        StandardEvaluationContext context = new StandardEvaluationContext();
        context.setPropertyAccessors(List.of(new JsonPropertyAccessor()));
        context.setRootObject(new ObjectMapper().readTree("{\"property\":[{\"name\":\"value1\"},{\"name\":\"value2\"}]}"));

        SpelExpressionParser parser = new SpelExpressionParser();

        System.out.println(parser.parseExpression("property.^[name != null].name").getValue(context));
        System.out.println(parser.parseExpression("property.^[name == 'value1'].name").getValue(context));
    }
}

in the console that prints :

value1
Exception in thread "main" org.springframework.expression.spel.SpelEvaluationException: EL1007E: Property or field 'name' cannot be found on null
    at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:213)
    at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:104)
    at org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:51)
    at org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:406)
    at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:92)
    at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:112)
    at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:272)
    at TestJsonAccessor.main(TestJsonAccessor.java:20)

Answer 1

The problem is here: name == 'value1'. That name is not a plain text to compare - it is a ToStringFriendlyJsonNode and to make it working expected with that equal operator you need to make it as string. Therefore like this:

property.^[name.toString() == 'value1'].name

There is another much longer way to reach the goal:

property.^[name.getTarget().asText() == 'value1'].name

The point of the JsonPropertyAccessor it to make a final result end-user friendly. In the middle it is still some JSON object we need to deal with.