Groovy Grails: Little joys
Originally published .
I’m working on a Groovy Grails project and I’ve just written a controller that takes a post from a form with only a partial representation of the object. Full representation of the object in the form is easy just do this:
myObj.properties = params
myObj.save()
The properties save to the Database without much fuss and if the data is invalid we’ll toss back to the edit view with a bucket of error messages. But, what if I only wanted to update one field in my object from a form… or sub form… or Ajax call?
…take a look at this little slice of groovy:
public class testObj {
Long a
Long b
String c
}
def t = new testObj(a:0,b:1,c:"foo");
t.properties.each({
println it
});
def params = ['a':1,'b':2]
println "-----------"
params.keySet().each({
println it + "->" + params[it]
t[it] = params[it]
})
println "-----------"
t.properties.each({
println it
});
The output looks like this:
metaClass=groovy.lang.MetaClassImpl@157c2bd[class testObj]
class=class testObj
b=1
c=foo
a=0
-----------
a->1
b->2
-----------
metaClass=groovy.lang.MetaClassImpl@157c2bd[class testObj]
class=class testObj
b=2
c=foo
a=1
What just happened? We mapped the values from a Map object onto the fields of an object with out knowing what the fields in the Java object were. Without introspection.
I presume this works with a POJO and if it does I’m going to go have a party tonight because I think web form processing, ETL, and a whole mess of other ORM type activities just got a helluva lot easier in Java land.
Aren’t you happy?