我用find代替:
find("from domain d where d.id=? AND d.name=?",[params.id,params.name])
这给了我第一个匹配的结果.
现在我看到有findWhere()用于:
Book.findWhere(author: params.author,title: params.title)
还返回第一个匹配的结果集.
什么是基本区别以及何时使用.
先感谢您.
解决方法
是的,所以我创建了一个测试应用程序,创建了一个测试Domain类:
package test class Book { String title String author static constraints = { } }
在Bootstrap中添加了一些虚拟数据:
import test.* class BootStrap { def init = { servletContext -> new Book( title:'Book 1',author:'Tim' ).save() new Book( title:'Book 2',author:'Alice' ).save() new Book( title:'Book 3',author:'Bob' ).save() } def destroy = { } }
还有一个测试控制器:
package test import grails.converters.JSON class BookController { def test1() { Book b = Book.find( "from Book as b where b.author = ? and b.title = ?",[ 'Tim','Book 1' ] ) render b as JSON } def test2() { Book b = Book.findWhere( author:'Tim',title:'Book 1' ) render b as JSON } def test3() { Book b = Book.findByAuthorAndTitle( 'Tim','Book 1' ) render b as JSON } }
然后,通过添加打开休眠日志记录
trace 'org.hibernate.type' debug 'org.hibernate.sql'
到Config的log4j部分,并且:
logsql = true
到DataSource.groovy的dataSource部分.
然后,运行所有3种控制器方法.
找到执行:
select book0_.id as id0_,book0_.version as version0_,book0_.author as author0_,book0_.title as title0_ from book book0_ where book0_.author=? and book0_.title=? limit ?
findWhere执行:
select this_.id as id0_0_,this_.version as version0_0_,this_.author as author0_0_,this_.title as title0_0_ from book this_ where (this_.author=? and this_.title=?) limit ?
findByAuthorAndTitle给了我们:
select this_.id as id0_0_,this_.title as title0_0_ from book this_ where this_.author=? and this_.title=? limit ?
正如您所看到的,在这个简单的例子中,他们只是说出同样事情的3种方式