如何动态忽略Jackson序列化中的属性

Question

我有一个具有多个@ManyToOne关联的实体.我使用spring-boot应用程序来公开REST API.目前我有多个REST API,返回整个实体的json响应,包括关联.

但我不想序列化所有REST API中的所有关联对象.例如

API-1应该返回父+ associationA对象API-2应该返回父+ associationA + associationB对象API-3应该返回父+ associationB + associationc + associationD

因此,在我的序列化过程中,我想忽略除了API-1的associationA之外的所有关联.对于API-2,我想忽略除A和B之外的其他关联

如何在Jackson序列化期间动态忽略这些属性.

注意:我有一个相同的类,我不想为每个API创建任何dto

任何建议都受到王者的赞赏.

Answer 1

我已经在Jackson中整理了三种方法来执行动态过滤.其中一个必须满足您的需求.

运用 @JsonView

你可以使用@JsonView:

public class Views {         
    interface Simple { }  
    interface Detailed extends Simple { }   
}

public class Foo {

    @JsonView(Views.Simple.class)
    private String name;

    @JsonView(Views.Detailed.class)
    private String details;

    // Getters and setters
}

@RequestMapping("/foo")
@JsonView(Views.Detailed.class)
public Foo getFoo() {
    Foo foo = new Foo();
    return foo;
}

或者,您可以动态设置视图MappingJacksonValue.

@RequestMapping("/foo")
public MappingJacksonValue getFoo() {
    Foo foo = new Foo();
    MappingJacksonValue result = new MappingJacksonValue(foo);
    result.setSerializationView(Views.Detailed.class);
    return result;
}

用一个 BeanSerializerModifier

您可以扩展BeanSerializerModifier然后覆盖该changeProperties()方法.它允许您根据需要添加,删除或替换任何序列化属性:

public class CustomSerializerModifier extends BeanSerializerModifier {

    @Override
    public List<BeanPropertyWriter> changeProperties(SerializationConfig config,
        BeanDescription beanDesc, List<BeanPropertyWriter> beanProperties) {

        // In this method you can add, remove or replace any of passed properties

        return beanProperties;
    }
}

然后将序列化程序注册为以下模块ObjectMapper:

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new SimpleModule() {

    @Override
    public void setupModule(SetupContext context) {
        super.setupModule(context);
        context.addBeanSerializerModifier(new CustomSerializerModifier());
    }
});

在这里和这里检查示例.

使用@JsonFilter一个SimpleBeanPropertyFilter

另一种方法涉及@JsonFilter:

@JsonFilter("customPropertyFilter")
public class Foo {

    private String name;
    private String details;

    // Getters and setters
}

根据您的需要扩展SimpleBeanPropertyFilter和覆盖该serializeAsField()方法:

public class CustomPropertyFilter extends SimpleBeanPropertyFilter {

    @Override
    public void serializeAsField(Object pojo, JsonGenerator jgen,
                                 SerializerProvider provider, 
                                 PropertyWriter writer) throws Exception {

        // Serialize a field
        // writer.serializeAsField(pojo, jgen, provider, writer);

        // Omit a field from serialization
        // writer.serializeAsOmittedField(pojo, jgen, provider);
    }
}

然后在您的注册中注册过滤器ObjectMapper:

FilterProvider filterProvider = new SimpleFilterProvider()
        .addFilter("customPropertyFilter", new CustomPropertyFilter());

ObjectMapper mapper = new ObjectMapper();
mapper.setFilterProvider(filterProvider);

如果你想让你的过滤器"全局",也就是说,要应用于所有bean,你可以创建一个混合类并使用以下方法对其进行注释@JsonFilter("customPropertyFilter"):

@JsonFilter("customPropertyFilter")
public class CustomPropertyFilterMixIn {

}

然后将混合类绑定到Object:

mapper.addMixIn(Object.class, CustomPropertyFilterMixIn.class);