Freemarker Built-ins for strings

 https://freemarker.apache.org/docs/ref_builtins_string.html

fieldItem_index = 0

因為通常pk會放在第一個欄位
可以用這種比較笨的方式判斷

    <#if fieldItem_index = 0>
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    </#if>

ref:
https://freemarker.apache.org/docs/ref_directive_list.html#ref_list_accessing_state

output ${expression} in Freemarker

 https://stackoverflow.com/questions/5207613/how-to-output-expression-in-freemarker-without-it-being-interpreted 

This should print ${person.name}:

${r"${person.name}"}

From the freemarker docs