chore(example): add example for basic inheritance support

jsonschema-examples/src/main/java/com/github/victools/jsonschema/examples/InheritanceRefExample.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2023 VicTools.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.github.victools.jsonschema.examples;
+
+import com.fasterxml.classmate.ResolvedType;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.github.victools.jsonschema.generator.CustomDefinition;
+import com.github.victools.jsonschema.generator.CustomDefinitionProviderV2;
+import com.github.victools.jsonschema.generator.Option;
+import com.github.victools.jsonschema.generator.OptionPreset;
+import com.github.victools.jsonschema.generator.SchemaGenerationContext;
+import com.github.victools.jsonschema.generator.SchemaGenerator;
+import com.github.victools.jsonschema.generator.SchemaGeneratorConfig;
+import com.github.victools.jsonschema.generator.SchemaGeneratorConfigBuilder;
+import com.github.victools.jsonschema.generator.SchemaKeyword;
+import com.github.victools.jsonschema.generator.SchemaVersion;
+import java.time.LocalDate;
+
+/**
+ * Example created in response to <a href="https://github.com/victools/jsonschema-generator/issues/407">#407</a>.
+ * <br>
+ * Reference separate definitions for common super types. Show-casing capabilities; but not recommended due to risk of infinite loop.
+ */
+public class InheritanceRefExample implements SchemaGenerationExampleInterface {
+
+    @Override
+    public ObjectNode generateSchema() {
+        SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_2020_12, OptionPreset.PLAIN_JSON)
+                .with(Option.DEFINITIONS_FOR_ALL_OBJECTS);
+        // ignore all fields declared in super types
+        configBuilder.forFields()
+                .withIgnoreCheck(field -> !field.getDeclaringType().equals(field.getDeclarationDetails().getSchemaTargetType()));
+        // reference super types explicitly
+        configBuilder.forTypesInGeneral()
+                // including SubtypeResolver would result in a StackOverflowError as the super reference is again replaced with it subtypes
+                //.withSubtypeResolver(new SubtypeLookUpExample.ClassGraphSubtypeResolver())
+                .withCustomDefinitionProvider(new ParentReferenceDefinitionProvider());
+        SchemaGeneratorConfig config = configBuilder.build();
+        return new SchemaGenerator(config).generateSchema(TestType.class);
+    }
+
+    static class ParentReferenceDefinitionProvider implements CustomDefinitionProviderV2 {
+        @Override
+        public CustomDefinition provideCustomSchemaDefinition(ResolvedType javaType, SchemaGenerationContext context) {
+            if (javaType.getErasedType().getSuperclass() == null || javaType.getErasedType().getSuperclass() == Object.class) {
+                return null;
+            }
+            ResolvedType superType = context.getTypeContext().resolve(javaType.getErasedType().getSuperclass());
+            // two options here:
+            // 1. providing "null" as second parameter = multiple hierarchy levels are respected
+            // 2. providing "this" as second parameter = only one hierarchy level is respected
+            ObjectNode superTypeReference = context.createStandardDefinitionReference(superType, null);
+            ObjectNode definition = context.createStandardDefinition(javaType, this);
+            definition.withArray(context.getKeyword(SchemaKeyword.TAG_ALLOF))
+                    .add(superTypeReference);
+            return new CustomDefinition(definition, CustomDefinition.DefinitionType.STANDARD, CustomDefinition.AttributeInclusion.YES);
+        }
+    }
+
+    static class TestType {
+        public Book favoriteBook;
+        public Poster favoritePoster;
+    }
+
+    static class Book extends PrintPublication {
+        public int pageCount;
+    }
+
+    static class Poster extends PrintPublication {
+        public boolean forMovie;
+    }
+
+    static class PrintPublication extends Publication {
+        public String author;
+        public String publisher;
+    }
+
+    static class Publication {
+        public LocalDate published;
+        public String title;
+    }
+}

jsonschema-examples/src/test/java/com/github/victools/jsonschema/examples/ExampleTest.java

@@ -36,6 +36,7 @@ public class ExampleTest {
             ExternalRefAnnotationExample.class,
             ExternalRefPackageExample.class,
             IfThenElseExample.class,
+            InheritanceRefExample.class,
             JacksonDescriptionAsTitleExample.class,
             JacksonSubtypeDefinitionExample.class,
             StrictTypeInfoExample.class,

jsonschema-examples/src/test/resources/com/github/victools/jsonschema/examples/InheritanceRefExample-result.json

@@ -0,0 +1,56 @@
+{
+    "$schema" : "https://json-schema.org/draft/2020-12/schema",
+    "$defs" : {
+        "Book" : {
+            "type" : "object",
+            "properties" : {
+                "pageCount" : {
+                    "type" : "integer"
+                }
+            },
+            "$ref" : "#/$defs/PrintPublication"
+        },
+        "Poster" : {
+            "type" : "object",
+            "properties" : {
+                "forMovie" : {
+                    "type" : "boolean"
+                }
+            },
+            "$ref" : "#/$defs/PrintPublication"
+        },
+        "PrintPublication" : {
+            "type" : "object",
+            "properties" : {
+                "author" : {
+                    "type" : "string"
+                },
+                "publisher" : {
+                    "type" : "string"
+                }
+            },
+            "$ref" : "#/$defs/Publication"
+        },
+        "Publication" : {
+            "type" : "object",
+            "properties" : {
+                "published" : {
+                    "type" : "string",
+                    "format" : "date"
+                },
+                "title" : {
+                    "type" : "string"
+                }
+            }
+        }
+    },
+    "type" : "object",
+    "properties" : {
+        "favoriteBook" : {
+            "$ref" : "#/$defs/Book"
+        },
+        "favoritePoster" : {
+            "$ref" : "#/$defs/Poster"
+        }
+    }
+}