SpEL throws exception when accessing property on nonexistent variable

[vampireslove]

    @Test
    public void testSpel(){
        String expression = "#name == 'joy' || #age > 10 || #ab.type == 1 || #a == 10";
        HashMap<String, Object> paramMap = new HashMap<>();
        paramMap.put("age", 8);
        StandardEvaluationContext context = new StandardEvaluationContext();
        context.setVariables(paramMap);
        ExpressionParser parser = new SpelExpressionParser();
        org.springframework.expression.Expression exp =  parser.parseExpression(expression);
        Object result = exp.getValue(context);
        System.out.println(result);
    }

I expect the result output to be false, but an exception is thrown. Can this situation be optimized, when encountering non-existent data, it should be judged as unsatisfied instead of throwing an exception?

ERROR:

Exception in thread "main" org.springframework.expression.spel.SpelEvaluationException: EL1007E: Property or field 'type' cannot be found on null
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:219)
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:106)
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:53)
	at org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:412)
	at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:93)
	at org.springframework.expression.spel.ast.OpEQ.getValueInternal(OpEQ.java:42)
	at org.springframework.expression.spel.ast.OpEQ.getValueInternal(OpEQ.java:32)
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:212)
	at org.springframework.expression.spel.ast.OpOr.getBooleanValue(OpOr.java:56)
	at org.springframework.expression.spel.ast.OpOr.getValueInternal(OpOr.java:51)
	at org.springframework.expression.spel.ast.OpOr.getValueInternal(OpOr.java:37)
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:114)
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:273)

[vampireslove]

org.springframework spring-expression 6.2.6

[sbrannen]

Hi @vampireslove,

Congratulations on submitting your first issue for the Spring Framework! 👍

The behavior you have encountered is expected.

Any attempt to access a property on a null reference (or a nonexistent variable, which is the case in your example) will result in a SpelEvaluationException.

However, you can make your expression return false if you use the null-safe navigation operator (?.) which evaluates to null for #ab?.type in your example.

@Test
void testSpel() {
	ExpressionParser parser = new SpelExpressionParser();
	StandardEvaluationContext context = new StandardEvaluationContext();
	context.setVariable("age", 8);

	String expression = "#name == 'joy' || #age > 10 || #ab?.type == 1 || #a == 10";
	Expression exp = parser.parseExpression(expression);

	assertThat(exp.getValue(context, Boolean.class)).isFalse();
}

The above modified version of your example passes.

In light of that, I am closing this as "works as designed".

[vampireslove]

@sbrannen Thank you very much for your answer! But #ab.type == 1 than #ab?. type == 1 is simpler 。 This is especially true in the case of multi-level expressions .