Learn How to Filter Response in Spring Rest

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With our category entity, most of the time we will just use the fields code, description, and entityId. And to return a response filtered like that we will need a class from jackson-databind jar. This dependency should already be added to your project from spring-boot-starter-web or spring-boot-data-rest.

And this is how we do it.

[open CategoryController class, filteredCategory method]
Examining this method, we can see that the category object is wrapped inside a categoryResource class. It does the same thing as our categoryResourceAssembler so yes it’s another alternative.

[open CategoryResource class]
Take note that we defined a JSON_Filter string constant here.

But really the main focus of this lecture is about the bean property filter which filters out all the fields of the category class except the ones we specified. And wrapping this class inside a MappingJacksonValue which we return as the response. This approach is really powerful as we can send the fields that we need in the request parameter as a set of strings. Here we can, change the filters into code only or maybe code and entityId. Note that this approach works for both single and list of entities.

Run the application

[run the postman test]

Finally, I’ll be presenting another approach to return an entity response and that is by using a JsonView.

[open CategoryView class]
Normally, in an application, we show a specific set of fields for a given role. For simplicity let’s just say that we have Public for a promoter and Internal for a supervisor. And yes all fields accessible through public must also be accessible through internal as it has higher authority.

The first thing to do is to associate the fields with a view. Let’s check the business entity.

[open BusinessEntity class]
Notice that both code and description are associated with the Public view.

To apply the filter to the rest response we need to annotate the endpoint with @JsonView.

[open CategoryController class, filteredView method]

Run the application.

[run the postman tests]


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