1.@NotNull：不能為null，但可以為empty，(""," ","? ")

2.@NotEmpty：不能為null，而且長度必須大于0，(" ","? ")

3.@NotBlank：只能作用在String上，不能為null，而且調(diào)用trim()后，長度必須大于0

("test")? ? 即：必須有實際字符

@NotNull: The CharSequence, Collection, Map or Array object is not null,

but can be empty.

@NotEmpty: The CharSequence, Collection, Map or Array object is not null

and size > 0.

@NotBlank: The string is not null and the trimmed length is greater than

zero.

4.examples:

1.String name = null;

@NotNull: false

@NotEmpty:false

@NotBlank:false

2.String name = "";

@NotNull:true

@NotEmpty: false

@NotBlank: false

3.String name = " ";

@NotNull: true

@NotEmpty: true

@NotBlank: false

4.String name = "Great answer!";

@NotNull: true

@NotEmpty:true

@NotBlank:true

*參考鏈接：

http://stackoverflow.com/questions/17137307/in-hibernate-validator-4-1-what-is-the-difference-between-notnull-notempty