Grails 领域类用法

最新推荐文章于 2018-05-15 11:29:15 发布

转载最新推荐文章于 2018-05-15 11:29:15 发布 · 518 阅读

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1.addTo*

为领域类添加一对多或多对多的关系。

def fictBook = new Book(title:"IT")
def nonFictBook = new Book(title:"On Writing: A Memoir of the Craft")
def a = new Author(name:"Stephen King")
             .addToFiction(fictBook)       // 'fiction' is name of relationship property
             .addToNonFiction(nonFictBook) // 'nonFiction' is name of relationship property
             .save()

2.constraints

定义验证的约束。

class Book {
   String title
   Author author
   static constraints = {
        title(blank:false, nullable:false, size:5..150)	
        author(nullable:false)
   }	
}

3.count

统计数据库中领域类实例的个数。

def noOfBooks = Book.count()

4.countBy*

使用领域类的属性进行统计

class Book {
   Long id
   Long version
   String title
   Date releaseDate
   String author
}

def c = Book.countByTitle("The Shining")
c = Book.countByTitleAndAuthor("The Sum of All Fears", "Tom Clancy")
c = Book.countByReleaseDateBetween(firstDate, new Date())
c = Book.countByReleaseDateGreaterThanEquals(firstDate)
c = Book.countByTitleLike("%Hobbit%")
c = Book.countByTitleNotEqual("Harry Potter")
c = Book.countByReleaseDateIsNull()
c = Book.countByReleaseDateIsNotNull()

5.createCriteria

创建一个Grails的HibernateCriteriaBuilder，用于创建条件查询。

def c = Account.createCriteria()
def results = c.list {
	like("holderFirstName", "Fred%")
	and {
		between("balance", 500, 1000)
		eq("branch", "London")
	}
	maxResults(10)
	order("holderLastName", "desc")
}

6.delete

7.errors

Spring Errors接口的实例，可能包含数据绑定或验证的错误。

def user =  new User(params)
if(user.validate()) {
    // do something with user
}
else {
    user.errors.allErrors.each {
        println it
    }
}

8.discard

通知一次变更不进行持久化，等同于使用Hibernate的evict方法。只是为了防止Grails的自动持久化。

def b = Book.get(1)
b.title = "Blah"
b.discard() // changes won't be applied now

9.executeQuery

10.executeUpdate

11.exists

12.find

如果没有找到返回null。

// Dan brown's first book
Book.find("from Book as b where b.author='Dan Brown'")
// with a positional parameter
Book.find("from Book as b where b.author=?",['Dan Brown'])
// with a named parameter (since 0.5)
Book.find("from Book as b where b.author=:author",[author:'Dan Brown'])
// query by example
def b = new Book(author:"Dan Brown")
Book.find(b)

13.findAll

14.findAllBy*

15.findWhere

16.get

根据id获取领域类实例，找不到返回null

17.getAll

根据id集获取领域类实例。

18.hasErrors

如果在合法性验证、保存或数据绑定时发生错误返回true。

19.ident

20.list

21.listOrderBy

22.lock

主键使用uuid生成：

 static mapping = {
        version false
        //主键重新定义
        id generator:'uuid.hex',name:"uuid",colunm:"uuid"
    }

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