Why spring bean can support not only String[] but also String

Question

This is Spring bean source.

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Bean {
    @AliasFor("name")
    String[] value() default {};

    @AliasFor("value")
    String[] name() default {};

    Autowire autowire() default Autowire.NO;

    String initMethod() default "";

    String destroyMethod() default AbstractBeanDefinition.INFER_METHOD;

I had noticed that String[] value() default {};. It means that we have to use String Array. But I use the code below, passed a String there, It still works, please tell me why.

@Bean("user")
public UserBean get() {
    return new UserBean();
}

akuma8 · Answer 1 · 2017-10-26T10:51:26.707

2

In an array you can put 0 or several values, it's up to you. That simply means that you can give 0 or several aliases to your bean.

@Bean(value={"user","otherUser","..."})
public UserBean get() {
  return new UserBean();
}

EDIT Why "user" is accepted even if it's not an array?

So, in Java you can declare a String object like this :

String value = "value1"; //this is a String
String user = "user"; // this is another String
String str = ""; //this is an empty string

Note that they are defined with "", so "user" is a String.

Now in this case whe have an array of String, that means we have an object which is a container of String.

String[] values=new String[]{};//this is an array of String, an object where we can put many Strings.

As "user" is a String, you can put it int the array values, something like this :

values[0]="user";

When you declare you bean like this :

@Bean("user")
public UserBean get() {
  return new UserBean();
}

In reality, you put the String "user" in the array of strings returned by the method :

String[] value() default {};

That why "user" is accepted because it's simply a String

edited Oct 26 '17 at 10:51

answered Oct 24 '17 at 07:38

akuma8

4,160
5
46
82

But in `@Bean("user")`, `"user"` is not a array. Can java support it? – Smith Cruise Oct 24 '17 at 08:02
1

I think you misunderstood what is an array in Java. Check here : https://alvinalexander.com/java/java-string-array-reference-java-5-for-loop-syntax – akuma8 Oct 24 '17 at 08:07
Did you see why `"user"` is accepted in this case or not? – akuma8 Oct 24 '17 at 12:15
sorry, I still don't understand it. Could you help me? – Smith Cruise Oct 26 '17 at 00:12
Please check the edit, I tryed to explain why `"user"` is accepted. – akuma8 Oct 26 '17 at 10:52

score 0 · Answer 2 · answered Oct 24 '17 at 08:10

0

This is the same concepts of the main method in Java.

public static void main(String[] args)

You can call your main method passing no parameters, one, two or how many you want.

answered Oct 24 '17 at 08:10

Serr

303
1
10

Why spring bean can support not only String[] but also String

2 Answers2