{"id":16323,"date":"2014-12-10T18:14:44","date_gmt":"2014-12-10T12:44:44","guid":{"rendered":"https:\/\/tothenewco.pro\/blog\/?p=16323"},"modified":"2014-12-10T18:14:44","modified_gmt":"2014-12-10T12:44:44","slug":"defining-a-bean-by-calling-function-on-another-bean","status":"publish","type":"post","link":"https:\/\/tothenewco.pro\/blog\/defining-a-bean-by-calling-function-on-another-bean\/","title":{"rendered":"Defining a bean by calling function on another bean"},"content":{"rendered":"

In Grails, We can define custom beans in resources.groovy. A simple bean definition looks like<\/p>\n

[java]
\nmyClass(MyClass)
\n[\/java]<\/p>\n

Read more about them here<\/a>. <\/p>\n

Recently, I wanted to define a bean, where the bean’s constructor required me to call a method on another bean to be instantiated.<\/p>\n

To make it more clear, Let us consider a class A which has a method getApi() in it. Consider another class B, now to define class B as a spring bean we need to call getApi() method of class A (which itself is a spring bean) in the constructor of B.<\/p>\n

In code the dependency is like this<\/p>\n

[java]
\nA a = new A()
\nB b = new B(a.getApi())
\n[\/java]<\/p>\n

The only complication being both A and B needed to be spring defined singleton beans in resources.groovy.<\/p>\n

Lets see how we can solve this problem, In resources.groovy <\/p>\n

[java]
\na(A)
\nb(B) { beanDefinition ->
\n beanDefinition.constructorArgs = ["#{a.getApi()}"]
\n}<\/p>\n

[\/java]<\/p>\n

In the above code, we defined the constructor arguments for class B, as a list containing only 1 element, which is a method invoked on bean “a”. <\/p>\n

Now to use these 2 beans in a third class “C” is trivial, in resources.groovy just do<\/p>\n

[java]<\/p>\n

c(C) {
\n a = ref("a")
\n b = ref("b")
\n}
\n[\/java]<\/p>\n

~~Cheers~~<\/p>\n

Sachin Anand
\nsachin[at]intelligrape[dot]com
\n@babasachinanand<\/p>\n","protected":false},"excerpt":{"rendered":"

In Grails, We can define custom beans in resources.groovy. A simple bean definition looks like [java] myClass(MyClass) [\/java] Read more about them here. Recently, I wanted to define a bean, where the bean’s constructor required me to call a method on another bean to be instantiated. To make it more clear, Let us consider a […]<\/p>\n","protected":false},"author":14,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":24,"footnotes":""},"categories":[7],"tags":[1573,1569,1572,1570,1571,4841],"class_list":["post-16323","post","type-post","status-publish","format-standard","hentry","category-grails","tag-bean-dependency","tag-beans","tag-constructor","tag-resources","tag-resources-groovy","tag-spring"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t