java - 两种 EL 语法有什么区别？

Question

我想让表单字段在 JSP 表单中稳定，所以我使用:

${param.fieldName}

我试过这样做:

${param["fieldame"]}

并且也有效!

有人能告诉我有什么区别吗？

Answer 1

来自 Expression Language Specification Version 2.2 Maintenance Release :

1.6 Operators [] and .

expr-a.identifier-b is equivalent to expr-a["identifier-b"]; that is, the identifier identifier-b is used to construct a literal whose value is the identifier, and then the [] operator is used with that value.