Is it possible to specify a schema for the writing part of Jackson with springboot.
For instance:
I have two pojo classes.
class A {
int a;
B b;
public A() { }
// Getter and Setter
}
class B {
double d;
String s;
public B() { }
// Getter and Setter
}
And I have a service
public SomeClass {
@RequestMapping(path = "/mapping", method = RequestMethod.POST)
public A recupererPESRetourDepuisPlateformeBLES()
return callToSomeMethodThatReturnsA();
}
}
Is there a way to specify that for the return type I want:
the attribute a and b of my object A and the attribute s of the object B.
I want the client to somehow send what we want to the server and the server parses the schema required and returns only it.
I know about @JsonIgnore and @JsonProperty.
I also know GraphQL but I want to stay with Jackson.
Update 1
Example:
I have instantiated in Java such a structure (here represented in JSON to simplify)
"A" {
"a": 12,
"b": {
"d": 23.362,
"s": "Hello world"
}
}
After my request, I want the server to send to the client:
"A" {
"a": 12,
"b": {
"s": "Hello world"
}
}
I don't know what kind of data my client can send to my server to specify the schema of data I want as output. This is part of the question.
CodePudding user response：
Spring boot dynamic filtering concept should help in this case. Modify the return type of the method recupererPESRetourDepuisPlateformeBLES() to MappingJacksonValue . Here are the code changes needed to be made:
import com.fasterxml.jackson.databind.ser.FilterProvider;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
public SomeClass {
@RequestMapping(path = "/mapping", method = RequestMethod.POST)
public MappingJacksonValue recupererPESRetourDepuisPlateformeBLES()
SimpleBeanPropertyFilter propertyFilter = SimpleBeanPropertyFilter.filterOutAllExcept("s");
FilterProvider filterProvider = new SimpleFilterProvider().addFilter("dynamicFilter", propertyFilter);
B b = new B();
b.setD(1d);
b.setS("someString");
A a = new A();
a.setA(1);
a.setB(b);
MappingJacksonValue value = new MappingJacksonValue(a);
value.setFilters(filterProvider);
return value;
}
}
Annotate the target Response class with @JsonFilter like below
import com.fasterxml.jackson.annotation.JsonFilter;
@JsonFilter("dynamicFilter")
public class B {
double d;
String s;
public B() {
}
}
Hope. This should solve the problem.
CodePudding user response：
I assume that you want to be able to do deep filtering ( be able to filter based on properties of classes A and B). To achieve that you can use following filter:
package com.example.demo.filter;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonStreamContext;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair;
import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
import com.fasterxml.jackson.databind.ser.PropertyFilter;
import com.fasterxml.jackson.databind.ser.PropertyWriter;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.fasterxml.jackson.module.jaxb.JaxbAnnotationIntrospector;
import java.util.Set;
/**
* Sample filtering fields durring json marshalling.
*/
public class JSON {
private static final String DEFAULT_FILTER = "__default";
private static final String DOT = ".";
private static final ObjectMapper MAPPER = new ObjectMapper().setAnnotationIntrospector(
new AnnotationIntrospectorPair(
new FilteringAnnotationInpector(), new JaxbAnnotationIntrospector(TypeFactory.defaultInstance())
)
);
public static String asString(Object object, Set<String> fields) {
PropertyFilter filter = filter(fields);
SimpleFilterProvider provider = new SimpleFilterProvider();
provider.addFilter(DEFAULT_FILTER, filter);
try {
return MAPPER.writer(provider).writeValueAsString(object);
} catch (JsonProcessingException ex) {
throw new RuntimeException("failed to marshall", ex);
}
}
private static PropertyFilter filter(Set<String> fields) {
PropertyFilter filter;
if (fields.size() > 0) {
filter = new DeepFieldFilter(fields);
} else {
filter = SimpleBeanPropertyFilter.serializeAll();
}
return filter;
}
private static class FilteringAnnotationInpector extends JacksonAnnotationIntrospector {
private static final long serialVersionUID = -8722016441050379430L;
@Override
public String findFilterId(Annotated a) {
return DEFAULT_FILTER;
}
}
private static class DeepFieldFilter extends SimpleBeanPropertyFilter {
private final Set<String> includes;
private DeepFieldFilter(Set<String> includes) {
this.includes = includes;
}
private String createPath(PropertyWriter writer, JsonGenerator jgen) {
StringBuilder path = new StringBuilder();
path.append(writer.getName());
JsonStreamContext sc = jgen.getOutputContext();
if (sc != null) {
sc = sc.getParent();
}
while (sc != null) {
if (sc.getCurrentName() != null) {
if (path.length() > 0) {
path.insert(0, DOT);
}
path.insert(0, sc.getCurrentName());
}
sc = sc.getParent();
}
return path.toString();
}
@Override
public void serializeAsField(Object pojo, JsonGenerator gen, SerializerProvider provider, PropertyWriter writer)
throws Exception {
String path = createPath(writer, gen);
if (includes.contains(path)) {
writer.serializeAsField(pojo, gen, provider);
} else {
writer.serializeAsOmittedField(pojo, gen, provider);
}
}
}
}
Here is complete example how to use this.
So, for example, if you want to return only property "a" of object A, first you will create controller method like this:
@GetMapping("/test")
public String test(@RequestBody Set<String> filterFields) {
B b = new B();
b.setD(23);
b.setS("b test");
A a = new A();
a.setA(1);
a.setB(b);
return JSON.asString(a, filterFields);
}
And if you send request like this:
The output should be {"a":1}
If you want to display property b of A class, with field s, you will send request like this:
And the output shoud be {"b":{"s":"b test"}}
As far as I can see, there is no other way to achieve what you want (using just Jackson).