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Find @JsonSetter(nulls = Nulls.AS_EMPTY) on empty collection fields

org.openrewrite.java.jackson.FindJsonSetterNullsAsEmptyCollections

Find Map and Collection fields that carry @JsonSetter(nulls = Nulls.AS_EMPTY), are initialized with an empty collection, and are no longer hidden by @JsonIgnore on the field or its getter, or by a class level @JsonIgnoreProperties. In rewrite-jackson 1.17.0 through 1.28.0 the Jackson 2 to 3 migration replaced @JsonIgnore with @JsonSetter(nulls = Nulls.AS_EMPTY) on exactly these fields, which starts serializing properties that were deliberately hidden wherever the field is otherwise visible, such as through a getter. Run this recipe to audit repositories migrated with those versions; every match that should stay out of the JSON output needs @JsonIgnore restored, which the addJsonIgnore option does for you.

Tags​

Recipe source​

GitHub: FindJsonSetterNullsAsEmptyCollections.java, Issue Tracker, Code Genome Project

This recipe is available under the Apache License Version 2.0.

Options​

TypeNameDescriptionExample
BooleanaddJsonIgnoreOptional. Add @JsonIgnore back to every match instead of only marking it, removing the @JsonSetter(nulls = Nulls.AS_EMPTY) that replaced it where nulls is its only argument. Only enable this once you have confirmed that none of the matches should be serialized. Defaults to false.

Example​

Parameters​
ParameterValue
addJsonIgnorenull
Before​
import com.fasterxml.jackson.annotation.JsonSetter;
import com.fasterxml.jackson.annotation.Nulls;
import java.util.LinkedHashMap;
import java.util.Map;

class Model {
    @JsonSetter(nulls = Nulls.AS_EMPTY)
    private Map<String, Object> additionalProperties = new LinkedHashMap<>();

    public Map<String, Object> getAdditionalProperties() {
        return additionalProperties;
    }
}
After​
import com.fasterxml.jackson.annotation.JsonSetter;
import com.fasterxml.jackson.annotation.Nulls;
import java.util.LinkedHashMap;
import java.util.Map;

class Model {
    /*~~(Verify this field should be serialized; `@JsonIgnore` may have been removed here)~~>*/@JsonSetter(nulls = Nulls.AS_EMPTY)
    private Map<String, Object> additionalProperties = new LinkedHashMap<>();

    public Map<String, Object> getAdditionalProperties() {
        return additionalProperties;
    }
}

Usage​

This recipe has no required configuration options. It can be activated by adding a dependency on `org.openrewrite.recipe:rewrite-jackson` in your build file or by running a shell command (in which case no build changes are needed):

OpenRewrite artifacts are distributed through the Code Genome Project repository (https://artifacts.codegenomeproject.org/maven), which requires authentication. Sign in to the Code Genome Project to create a download token, then in the snippets below replace USERNAME with the email or username you signed in with and TOKEN with that token. See the quickstart guide for details.

  1. Add the following to your build.gradle file:
    build.gradle
    plugins {
        id("org.openrewrite.rewrite") version("latest.release")
    }

    rewrite {
        activeRecipe("org.openrewrite.java.jackson.FindJsonSetterNullsAsEmptyCollections")
        setExportDatatables(true)
    }

    repositories {
        mavenCentral()
        maven {
            url = "https://artifacts.codegenomeproject.org/maven"
            credentials {
                username = "USERNAME"
                password = "TOKEN"
            }
        }
    }

    dependencies {
        rewrite("org.openrewrite.recipe:rewrite-jackson:1.28.4")
    }
  2. Run gradle rewriteRun to run the recipe.

See how this recipe works across multiple open-source repositories​

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Data Tables​

Source files that had results​

org.openrewrite.table.SourcesFileResults

Source files that were modified by the recipe run.

Column NameDescription
Source path before the runThe source path of the file before the run. null when a source file was created during the run.
Source path after the runA recipe may modify the source path. This is the path after the run. null when a source file was deleted during the run.
Parent of the recipe that made changesIn a hierarchical recipe, the parent of the recipe that made a change. Empty if this is the root of a hierarchy or if the recipe is not hierarchical at all.
Recipe that made changesThe specific recipe that made a change.
Estimated time savingAn estimated effort that a developer to fix manually instead of using this recipe, in unit of seconds.
CycleThe recipe cycle in which the change was made.