How to use JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS

[farsunset]

The enum JsonParser.Feature.ALLOW_UNQUOTED_CONTROL_CHARS is Deprecated in version jackson-core 2.10.0. I see to use JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS. but i can't find api to use this. can who show a case use ObjectMapper? thanks

[cowtowncoder]

Usage can be done in 3 ways:

1. When constructing JsonFactory (needs new builder() approach)
2. When constructing JsonMapper (subtype of ObjectMapper, needs new builder() approach)
3. When creating ObjectReader instances

In first 2 of these, approach requires something like:

JsonFactory f = JsonFactory.builder().enable(... feature).build();
// or
JsonMapper m = JsonMapper.builder().enable(... feature).build();
// or, since `ObjectMapper` is base type, you can just use that
ObjectMapper m = JsonMapper.builder().enable(... feature).build();

Third approach might be easiest as you can use existing ObjectMapper:

ObjectReader r = mapper.readerFor(MyType.class).with(... feature...);
MyType value = r.readValue(source);

[farsunset]

it is very helpful. thanks

[amreladawy]

Actually, JsonMapper m = JsonMapper.builder().enable(... feature).build(); did not work. the enable method expects a JsonParser.Feature while JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS isJsonReadFeature.

I tried this JsonMapper m = JsonMapper.builder().enable(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.mappedFeature()).build();. but it has no effect. I had to revert back to the deprecated feature.

[cowtowncoder]

@amreladawy I can not reproduce this: works for me with Jackson 2.10.4, using either one of below:

        ObjectMapper MAPPER = new JsonMapper();
        Map<?, ?> result = MAPPER.readerFor(Map.class)
                .with(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS)
                .readValue(JSON);
        assertEquals(1, result.size());

        // and new mapper should work
        ObjectMapper mapper2 = JsonMapper.builder()
                .enable(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS)
                .build();
        result = mapper2.readerFor(Map.class)
                .readValue(JSON);

but if you can reproduce it with at test, specific Jackson version, please file an issue for jackson-databind.

[amreladawy]

@cowtowncoder Thanks for coming back to me on this closed issue. Here is the code

import com.fasterxml.jackson.core.json.JsonReadFeature
import com.fasterxml.jackson.databind.DeserializationFeature
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule
import org.glassfish.jersey.client.proxy.WebResourceFactory
import javax.ws.rs.client.ClientBuilder
import javax.ws.rs.ext.ContextResolver

inline fun <reified T> getApi(url: String): T = try {
        WebResourceFactory.newResource(T::class.java, ClientBuilder.newClient()
        .register(
            ContextResolver {
                ObjectMapper()
                    .enable(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.mappedFeature())
                    .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
                    .registerModule(Jdk8Module()).registerModule(ParameterNamesModule())
            }
        ).target(url))
} catch (e: Exception) {
    e.printStackTrace()
}

This is kotlin, but should not make any difference. I am using jakson 2.11.0

Here is the signature of the enable method.

    /**
     * Method for enabling specified {@link com.fasterxml.jackson.core.JsonParser.Feature}s
     * for parser instances this object mapper creates.
     *<p>
     * Note that this is equivalent to directly calling same method on {@link #getFactory}.
     *<p>
     * WARNING: since this method directly modifies state of underlying {@link JsonFactory},
     * it will change observed configuration by {@link ObjectReader}s as well -- to avoid
     * this, use {@link ObjectReader#with(JsonParser.Feature)} instead.
     *
     * @since 2.5
     */
    public ObjectMapper enable(JsonParser.Feature... features) {
        for (JsonParser.Feature f : features) {
            _jsonFactory.enable(f);
        }
        return this;
      }

There is not signature that accepts JsonReadFeature or FormatFeature

By the way, the above code worked and was able to activate the feature.

[cowtowncoder]

@amreladawy seems like you were trying to find ObjectMapper.enable(JsonReadFeature) which does not exist (correct).
What exists is JsonMapper.builder().enable(JsonReadFeature) (or ObjectReader.with(JsonReadFeature) ).
This is a bit confusing since your earlier example DID use builder approach (added in 2.10).

Deprecated variant does still work with 2.x for backwards-compatibility reasons and will not be removed until 3.0. So that is fine. It is deprecated as 3.0 will remove direct mutability of ObjectMapper (and lower level JsonFactory), so goal is to help developers migrate to new mechanism over time.

[amreladawy]

Thanks for your help on that.

[amittal1]

I think everyone figured it out already but just adding something which bugged me for a while before finally getting the solution. I didn't want to create to custom Mapper but continue using my application.properties file. If you are using spring-boot version 1.5.18 and using the application.properties file, then you can simply add one line in your application.properties file:
spring.jackson.parser.allow-unquoted-control-chars=true

No need to create custom Mapper or anything. This resolved my issue.

[cowtowncoder]

@amittal1 thank you for sharing this!

[zipper01]

I think everyone figured it out already but just adding something which bugged me for a while before finally getting the solution. I didn't want to create to custom Mapper but continue using my application.properties file. If you are using spring-boot version 1.5.18 and using the application.properties file, then you can simply add one line in your application.properties file:
spring.jackson.parser.allow-unquoted-control-chars=true

No need to create custom Mapper or anything. This resolved my issue.

Why you asume everyone is using spring?

[adamu]

I was having problems with using this via Jackson2ObjectMapperBuilderCustomizer and Jackson2ObjectMapperBuilder.featuresToEnable.

featuresToEnable accepts Objects, so replacing JsonParser.Feature.ALLOW_NON_NUMERIC_NUMBERS with JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS compiles, but fails at runtime with

org.springframework.beans.FatalBeanException: Unknown feature class: com.fasterxml.jackson.core.json.JsonReadFeature

I'm not sure why, but I worked around with JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.mappedFeature(), which uses the same value, but avoids the deprecation warning.

[channyeintun]

@amittal1 Thank you for sharing. :D

[He-Pin]

I'm not sure why it works when parsing the name-selector.json` in jsonpath-standard/jsonpath-compliance-test-suite#94