我在使用grails中获得多对多关系时遇到了一些问题.以下是否有任何明显错误：
class Person {
static hasMany = [friends: Person]
static mappedBy = [friends: 'friends']
String name
List friends = []
String toString() {
return this.name
}
}
class BootStrap {
def init = { servletContext ->
Person bob = new Person(name: 'bob').save()
Person jaq = new Person(name: 'jaq').save()
jaq.friends << bob
println "Bob's friends: ${bob.friends}"
println "Jaq's friends: ${jaq.friends}"
}
}
我希望Bob与Jaq成为朋友,反之亦然,但我在启动时得到以下输出：
Running Grails application.. Bob's friends: [] Jaq's friends: [Bob]
(我使用的是Grails 1.2.0)
解决方法
这似乎有效：
class Person {
static hasMany = [ friends: Person ]
static mappedBy = [ friends: 'friends' ]
String name
String toString() {
name
}
}
然后在BootStrap中：
class BootStrap {
def init = { servletContext ->
Person bob = new Person(name: 'bob').save()
Person jaq = new Person(name: 'jaq').save()
jaq.addToFriends( bob )
println "Bob's friends: ${bob.friends}"
println "Jaq's friends: ${jaq.friends}"
}
}
我得到以下内容：
Running Grails application.. Bob's friends: [jaq] Jaq's friends: [bob]