关于domain

domain是Grails的中心，因此，有必要对他多加关注。

1. 属性的类型必须定义

Grails是有Groovy实现的，依据Groovy的语法，以下代码是完全正确的，但是Grails整合了Hibernate和Spring，使用了GORM反射机制实现实体间的映射，所以在定义域类时不要使用def关键字来定义属性，务必明确定义属性类型。

在默认情况下，String映射到数据库中的字段类型是VARCHAR（Date映射到数据库中的字段类型是datetiR_86_11845@E），如果通过类变量conTraints定义了String的长度范围，且长度过长，映射到数据库中的字段类型会变为TEXT，十分智能。

class User <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> def <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d def re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d def address def <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er } 

class User <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> //有效 <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng address <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er } 

2.domain中属性的约束

domain中属性的约束条件在上一篇中都已经涉及了，只需要将其在consTraints中加以定义，就能实现。

class User <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> static cons<a href="http://code.js-code.com/tag/Trai/" target="_blank" class="keywords">Trai</a>nts = <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d(blank: <a href="http://code.js-code.com/tag/fal/" target="_blank" class="keywords">fal</a>s<a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E)</a> re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d(blank: <a href="http://code.js-code.com/tag/fal/" target="_blank" class="keywords">fal</a>se,validator: <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a>val,obj -> if (obj.<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">!=</a> val) <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> return "Re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d is not right" }}) } <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng address <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er } 

3. 调整界面上字段显示顺序

要跳转domain中的属性在界面上的显示顺序，只要在consTraints的闭包中调整期位置即可。

class User <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> static cons<a href="http://code.js-code.com/tag/Trai/" target="_blank" class="keywords">Trai</a>nts = <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er() address() <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d(blank: <a href="http://code.js-code.com/tag/fal/" target="_blank" class="keywords">fal</a>s<a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E)</a> re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d(blank: <a href="http://code.js-code.com/tag/fal/" target="_blank" class="keywords">fal</a>se,obj -> if (obj.<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">!=</a> val) <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> return "Re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d is not right" }}) } <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng address <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er } 

4. 重写toString()方法

重写toString()方法，对于得到我们需要的值，以及在GORM映射时显示都有很重要的作用。在重写中需要注意：toString的返回值不能定义为def类型，也不能使用闭包的方式重写，因为他重写的是java的Object类

class User <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> static cons<a href="http://code.js-code.com/tag/Trai/" target="_blank" class="keywords">Trai</a>nts = <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er() address() <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d(blank: <a href="http://code.js-code.com/tag/fal/" target="_blank" class="keywords">fal</a>s<a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E)</a> re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d(blank: <a href="http://code.js-code.com/tag/fal/" target="_blank" class="keywords">fal</a>se,obj -> if (obj.<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">!=</a> val) <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> return "Re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d is not right" }}) } <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng re<a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a>d <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng address <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng to<a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng() <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> "$<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a><a href="http://code.js-code.com/tag/passwor/" target="_blank" class="keywords">passwor</a><a href="http://code.js-code.com/tag/D/" target="_blank" class="keywords">D}</a>" + "," + "$<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a>address}" + "," + "$<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a><a href="http://code.js-code.com/tag/gend/" target="_blank" class="keywords">gend</a>er}" } }