@JsonIgnore的源码说明

Posted 2020-08-13

@JsonIgnore不仅仅是在getter上有影响，也对setter方法有影响：

所在包：com.fasterxml.jackson.annotation;

源码：

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Marker annotation that indicates that the annotated method or field is to be//标记方法或字段
 * ignored by introspection-based//被标记的方法和字段不进行序列化和反序列化
 * serialization and deserialization functionality. That is, it should
 * not be consider a "getter", "setter" or "creator".//实际上就是：这个注解不能被认为是一个getter,setter或creator
 *<p>
 * In addition, starting with Jackson 1.9, if this is the only annotation//1.9版本如果仅加入此注解，将会导致整个属性被忽视
 * associated with a property, it will also cause the whole
 * property to be ignored: that is, if setter has this annotation and//如果在setter上注解，在getter上不注解，那么getter也会受影响（将不会被序列化）
 * getter has no annotations, getter is also effectively ignored.
 * It is still possible for different accessors to use different//不同的存取器可以用不同的注解
 * annotations; so if only "getter" is to be ignored, other accessors//如果仅是getter加了此注解，那么其他的存取器（setter或字段）
 * (setter or field) would need explicit annotation to prevent//需要明确地被注解以防止不被序列化(通常使用@JsonProperty来注解）
 * ignoral (usually {@link JsonProperty}).
 * <p>
 * For example, a "getter" method that would otherwise denote
 * a property (like, say, "getValue" to suggest property "value")
 * to serialize, would be ignored and no such property would
 * be output unless another annotation defines alternative method to use.
 *<p>
 * Before version 1.9, this annotation worked purely on method-by-method (or field-by-field)
 * basis; annotation on one method or field did not imply ignoring other methods
 * or fields. However, with version 1.9 and above, annotations associated
 * with various accessors (getter, setter, field, constructor parameter) of
 * a logical property are combined; meaning that annotations in one (say, setter)
 * can have effects on all of them (if getter or field has nothing indicating
 * otherwise).
 *<p>
 * Annotation is usually used just a like a marker annotation, that
 * is, without explicitly defining ‘value‘ argument (which defaults
 * to <code>true</code>): but argument can be explicitly defined.
 * This can be done to override an existing JsonIgnore by explicitly
 * defining one with ‘false‘ argument.
 *<p>
 * Annotation is similar to {@link javax.xml.bind.annotation.XmlTransient} 
 */
@Target({ElementType.ANNOTATION_TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotation
public @interface JsonIgnore
{
    /**
     * Optional argument that defines whether this annotation is active
     * or not. The only use for value ‘false‘ if for overriding purposes
     * (which is not needed often); most likely it is needed for use
     * with "mix-in annotations" (aka "annotation overrides").
     * For most cases, however, default value of "true" is just fine
     * and should be omitted.
     */
    boolean value() default true;
}

 

JsonIgnore可以标注在字段、方法上（1.9版本及以上），当注解@JsonIgnore时，会发生两件事：

①：不会被jackson解析；

②：字段或方法所属的类不会成为持久化类