Spring in @NotNull, what is the difference between @NotEmpty and @NotBlank that?

Excerpt: https: //www.cnblogs.com/Terry-Wu/p/8134732.html

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Example:

String name = null;
@NotNull: false
@NotEmpty: false
@NotBlank: false

String name = "";
@NotNull: true
@NotEmpty: false
@NotBlank: false

String name = " ";
@NotNull: true
@NotEmpty: true
@NotBlank: false

String name = "Great answer!";
@NotNull: true
@NotEmpty: true
@NotBlank: true

　　

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Description of the three differences

@NotNull: // CharSequence, Collection, Map Array object and can not be null, but may be an empty set (size = 0).  
@NotEmpty: // CharSequence, Collection, Map and Array objects can not be null and size related objects greater than zero.  
@NotBlank: // String is not null and the length removed (trimmed length) after the two ends of the blank character is greater than 0.

　　

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Defined annotations (in version 4.1 in):

1, @ NotNull:

It is defined as follows:

@Constraint(validatedBy = {NotNullValidator.class})

This class has a method isValid is so defined:

public boolean isValid(Object object, ConstraintValidatorContext constraintValidatorContext) {  
 return object != null;    
} 

Object is not null on the line, the other is not guaranteed.

 

2、@NotEmpty：

It is defined as follows:

@NotNull    
@Size(min = 1)  　　

也就是说，@NotEmpty除了@NotNull之外还需要保证@Size(min=1)，这也是一个注解，这里规定最小长度等于1，也就是类似于集合非空。

　　

3、@NotBlank：

@NotNull    
@Constraint(validatedBy = {NotBlankValidator.class})  　

Similarly, in addition to @NotNull, there is defined a class, the class also has isValid method:

if ( charSequence == null ) {  //curious   
  return true;     
}     
return charSequence.toString().trim().length() > 0; 

　　

Interestingly, it returns true if the object is a null string when a method, but only if and when it returns false trimmed length of zero. Returns true even when the string is null when the method, but also contains @NotNull since @NotBlank, so @NotBlank claim string is not null.

　　

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