如何告诉Jackson在序列化期间忽略值为null的字段？

Question

如何告诉Jackson在序列化期间忽略值为null的字段？

858

Jackson如何配置，以在序列化期间忽略某个字段的值，如果该字段的值为null。

例如：

public class SomeClass {
   // what jackson annotation causes jackson to skip over this value if it is null but will 
   // serialize it otherwise 
   private String someValue; 
}

- ams

22个回答

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- mekdev · Answer 1

0

Jackson 2.x+ 使用

mapper.getSerializationConfig().withSerializationInclusion(JsonInclude.Include.NON_NULL);

- mekdev

.withSerializationInclusion(JsonInclude.Include.NON_NULL) 而不是对吧？ - herau

谢谢指出，我会暂时不升级 :-( - ZiglioUK

@ruslan：可能是因为getSerializationConfig()的文档中写道：“请注意，由于实例是不可变的，因此您无法通过访问实例并调用方法来更改设置：这只会创建配置对象的新实例。” - Zero3

- atom88 · Answer 2

另外，您必须更改使用文档中描述的Map myVariable的方法以消除null值的方法：

From documentation:
com.fasterxml.jackson.annotation.JsonInclude

@JacksonAnnotation
@Target(value={ANNOTATION_TYPE, FIELD, METHOD, PARAMETER, TYPE})
@Retention(value=RUNTIME)
Annotation used to indicate when value of the annotated property (when used for a field, method or constructor parameter), or all properties of the annotated class, is to be serialized. Without annotation property values are always included, but by using this annotation one can specify simple exclusion rules to reduce amount of properties to write out.

*Note that the main inclusion criteria (one annotated with value) is checked on Java object level, for the annotated type, and NOT on JSON output -- so even with Include.NON_NULL it is possible that JSON null values are output, if object reference in question is not `null`. An example is java.util.concurrent.atomic.AtomicReference instance constructed to reference null value: such a value would be serialized as JSON null, and not filtered out.

To base inclusion on value of contained value(s), you will typically also need to specify content() annotation; for example, specifying only value as Include.NON_EMPTY for a {link java.util.Map} would exclude Maps with no values, but would include Maps with `null` values. To exclude Map with only `null` value, you would use both annotations like so:
public class Bean {
   @JsonInclude(value=Include.NON_EMPTY, content=Include.NON_NULL)
   public Map<String,String> entries;
}

Similarly you could Maps that only contain "empty" elements, or "non-default" values (see Include.NON_EMPTY and Include.NON_DEFAULT for more details).
In addition to `Map`s, `content` concept is also supported for referential types (like java.util.concurrent.atomic.AtomicReference). Note that `content` is NOT currently (as of Jackson 2.9) supported for arrays or java.util.Collections, but supported may be added in future versions.
Since:
2.0