java - Spring Expression Language - List 上的 Size 属性

Question

我正在尝试使用 Spring EL 在 List 上使用 size 属性，这会抛出无法找到大小的异常。

@Cacheable(value = "cache", unless = "#result.size > 0")
public List<Results> getResult();

异常(exception):

org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 8): Field or property 'size' cannot be found on object of type 'java.util.ArrayList'
        at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:217)
        at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:85)
        at org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:43)
        at org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:346)
        at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:84)

Answer 1

size 解析为不存在的 List#getSize()。尝试使用 size() 如下:

@Cacheable(value = "cache", unless = "#result.size() > 0")
public List<Results> getResult();