chore: add example for target type override (#452)

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

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2024 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.FieldScope;
+import com.github.victools.jsonschema.generator.MemberScope;
+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.SchemaVersion;
+import com.github.victools.jsonschema.generator.SubtypeResolver;
+import com.github.victools.jsonschema.generator.TypeContext;
+import com.github.victools.jsonschema.module.jakarta.validation.JakartaValidationModule;
+import io.github.classgraph.ClassGraph;
+import io.github.classgraph.ClassInfoList;
+import io.github.classgraph.ScanResult;
+import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.Size;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Example created in response to <a href="https://github.com/victools/jsonschema-generator/discussions/451">#451</a>.
+ * <br/>
+ * Demonstrating target type overrides to represent a {@code byte[]} as {@code string} with particular content encoding.
+ */
+public class TargetTypeOverrideExample implements SchemaGenerationExampleInterface {
+
+    @Override
+    public ObjectNode generateSchema() {
+        SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_2020_12, OptionPreset.PLAIN_JSON);
+        configBuilder.with(new JakartaValidationModule());
+        configBuilder.forFields()
+                .withTargetTypeOverridesResolver(this::treatByteArrayAsString)
+                .withInstanceAttributeOverride(this::addContentEncodingForByteArray);
+        SchemaGeneratorConfig config = configBuilder.build();
+        SchemaGenerator generator = new SchemaGenerator(config);
+        return generator.generateSchema(Example.class);
+    }
+
+    private List<ResolvedType> treatByteArrayAsString(MemberScope<?, ?> scope) {
+        ResolvedType type = scope.getType();
+        if (type != null && type.getErasedType().equals(byte[].class)) {
+            return Collections.singletonList(scope.getContext().resolve(String.class));
+        }
+        return null;
+    }
+
+    private void addContentEncodingForByteArray(ObjectNode schema, MemberScope<?, ?> scope, SchemaGenerationContext context) {
+        ResolvedType declaredType = scope.getDeclaredType();
+        if (declaredType != null && declaredType.getErasedType().equals(byte[].class)) {
+            schema.put("contentEncoding", "base64");
+        }
+    }
+
+    static class Example {
+        @NotNull
+        @Size(min = 1, max = 100)
+        public String someText;
+        @NotNull
+        @Size(min = 1, max = 10485760)
+        public byte[] byteArray;
+    }
+}

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

@@ -41,6 +41,7 @@ public class ExampleTest {
             JacksonSubtypeDefinitionExample.class,
             StrictTypeInfoExample.class,
             SubtypeLookUpExample.class,
+            TargetTypeOverrideExample.class,
             ValidationErrorMessageExample.class
     })
     public void testExample(Class<? extends SchemaGenerationExampleInterface> exampleType) throws Exception {

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

@@ -0,0 +1,17 @@
+{
+    "$schema" : "https://json-schema.org/draft/2020-12/schema",
+    "type" : "object",
+    "properties" : {
+        "byteArray" : {
+            "type" : "string",
+            "minLength" : 1,
+            "maxLength" : 10485760,
+            "contentEncoding" : "base64"
+        },
+        "someText" : {
+            "type" : "string",
+            "minLength" : 1,
+            "maxLength" : 100
+        }
+    }
+}