Beside injecting a simple value (using the value attribute) and a reference to other bean (using the ref attribute). We can also inject collections properties into a bean.
Spring provides four ways to inject collections. There are <list> and <set> that can be used to inject arrays or any implementation of java.util.Collection. The <map> that can be used to inject property of type java.util.Map. And the <props> can be used to inject property of type java.util.Properties.
Here is a table that summarize the collection configuration support in Spring.
| Collection Element | Description |
|---|---|
<list> |
Wiring a list of values, where the values might have duplicates. |
<set> |
Wiring a set of values, where the values can not have duplicates. |
<map> |
Wiring a key-value pairs collection, where the key and value can be any type |
<props> |
Wiring a key-value pairs property, where the key and value are both type of String |
You can see the following example on how to use each type of this collection configuration: