在springboot中发送响应时，我们是否有任何注释来验证响应属性/字段不是null？

Question

Below is the 'Student' response class with getter and setter, I am setting the values with the help of setter, with the help of null checks in codes, it can be done but do we have any annotations for that?

 Class Student
    {
     String name;
     String rollno;
     String collegeName;
    
     //Getter and setter
   }

Answer 1

There are two ways to perform validation: Implement your own utility class for validation of objects and validate objects prior passing to some method or use @Valid annotation on your objects you are going pass to the method:

public void saveStudent(@Valid Student student);

In your Student class required String fields must be annotated with @NotBlank or NotNull for other types.

Don't forget to add required dependencies for validation such as:

<dependency>
    <groupId>org.hibernate.validator</groupId>
    <artifactId>hibernate-validator-annotation-processor</artifactId>
    <version>6.0.2.Final</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

Answer 2

This is what you can do with your response class:

@Data
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
public class ResponseClass implements Serializable {

}

This is will not include null and unknown fields in your response json.

Answer 3

You can try to use @NonNull annotation from Lombok ( link )

Assume your class is:

@Getter
@Setter
@AllArgsConstructor
public class Student {

    @NonNull private String name;
    @NonNull private String rollno;
    @NonNull private String collegeName;
}

And here is the test:

@Test
void CreateStudent() {
    Assertions.assertThrows(NullPointerException.class, () -> new Student("John", "42", null));
}

update

In your case (no custom constructors, only default), yo should add @NonNull annotation to your setter:

public void setName(@NonNull String name) {
    this.name = name;
}

And here is the test:

@Test
void CreateStudent() {
    Student student = new Student();
    Assertions.assertThrows(NullPointerException.class, () -> student.setName(null));
}