feature: add GSON module

jsonschema-generator-parent/pom.xml

@@ -165,6 +165,7 @@
         <version.swagger-2>2.2.5</version.swagger-2>
         <!-- maven plugin runtime dependencies -->
         <version.classgraph>4.8.149</version.classgraph>
+        <version.gson>2.11.0</version.gson>
     </properties>
 
     <dependencyManagement>
@@ -211,6 +212,11 @@
                 <artifactId>classgraph</artifactId>
                 <version>${version.classgraph}</version>
             </dependency>
+            <dependency>
+                <groupId>com.google.code.gson</groupId>
+                <artifactId>gson</artifactId>
+                <version>${version.gson}</version>
+            </dependency>
         </dependencies>
     </dependencyManagement>
     <dependencies>

jsonschema-module-gson/README.md

@@ -0,0 +1,64 @@
+# Java JSON Schema Generation – Module Gson
+[![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.github.victools/jsonschema-module-jackson/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.github.victools/jsonschema-module-jackson)
+
+Module for the [jsonschema-generator](../jsonschema-generator) – deriving JSON Schema attributes from `gson` annotations.
+
+## Features
+1. Override a field's/method's property name as per `@SerializedName` annotations.
+2. Ignore fields/methods that are marked with a `@Expose` annotation.
+
+----
+
+## Documentation
+JavaDoc is being used throughout the codebase, offering contextual information in your respective IDE or being available online through services like [javadoc.io](https://www.javadoc.io/doc/com.github.victools/jsonschema-module-jackson).
+
+Additional documentation can be found in the [Project Wiki](https://github.com/victools/jsonschema-generator/wiki).
+
+----
+
+## Usage
+### Dependency (Maven)
+```xml
+<dependency>
+    <groupId>com.github.victools</groupId>
+    <artifactId>jsonschema-module-gson</artifactId>
+    <version>[4.21.0,5.0.0)</version>
+</dependency>
+```
+
+Since version `4.7`, the release versions of the main generator library and this module are aligned.
+It is recommended to use identical versions for both dependencies to ensure compatibility.
+
+### Code
+#### Passing into SchemaGeneratorConfigBuilder.with(Module)
+```java
+import com.github.victools.jsonschema.generator.SchemaGeneratorConfigBuilder;
+import com.github.victools.jsonschema.generator.SchemaVersion;
+import com.github.victools.jsonschema.module.gson.GsonModule;
+```
+```java
+GsonModule module = new GsonModule();
+SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_2019_09)
+    .with(module);
+```
+
+#### Complete Example
+```java
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.victools.jsonschema.generator.OptionPreset;
+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.module.gson.GsonModule;
+```
+```java
+GsonModule module = new GsonModule();
+SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_2019_09, OptionPreset.PLAIN_JSON)
+    .with(module);
+SchemaGeneratorConfig config = configBuilder.build();
+SchemaGenerator generator = new SchemaGenerator(config);
+JsonNode jsonSchema = generator.generateSchema(YourClass.class);
+
+System.out.println(jsonSchema.toString());
+```

jsonschema-module-gson/pom.xml

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.github.victools</groupId>
+        <artifactId>jsonschema-generator-parent</artifactId>
+        <version>4.35.0</version>
+        <relativePath>../jsonschema-generator-parent/pom.xml</relativePath>
+    </parent>
+    <artifactId>jsonschema-module-gson</artifactId>
+
+    <name>Java JSON Schema Generator Module – GSON</name>
+    <description>Module for the jsonschema-generator – deriving JSON Schema attributes from GSON annotations</description>
+    <url>https://github.com/victools/jsonschema-generator</url>
+
+    <properties>
+        <java.module.name>com.github.victools.jsonschema.module.gson</java.module.name>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.github.victools</groupId>
+            <artifactId>jsonschema-generator</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <artifactId>maven-source-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <artifactId>maven-javadoc-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <groupId>org.moditect</groupId>
+                <artifactId>moditect-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

jsonschema-module-gson/src/main/java/com/github/victools/jsonschema/module/gson/GsonModule.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2019 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.module.gson;
+import com.github.victools.jsonschema.generator.Module;
+import com.github.victools.jsonschema.generator.SchemaGeneratorConfigBuilder;
+import com.google.gson.annotations.Expose;
+import com.google.gson.annotations.SerializedName;
+import java.util.Optional;
+
+/**
+ * Module for setting up schema generation aspects based on {@code gson-annotations}.
+ * <ul>
+ * <li>Apply alternative property names defined in {@link SerializedName} annotations.</li>
+ * <li>Exclude properties that are deemed to be ignored per the use of {@link Expose}.</li>
+ * </ul>
+ */
+public class GsonModule implements Module {
+
+    /**
+     * Constructor, without any additional options.
+     *
+     * @see GsonModule
+     */
+    public GsonModule() {
+    }
+
+    @Override
+    public void applyToConfigBuilder(SchemaGeneratorConfigBuilder builder) {
+        //if the field should be included yes/no based on GSON Expose declaration
+        builder.forFields().withIgnoreCheck(field -> {
+            Expose annotation = field.getAnnotationConsideringFieldAndGetter(Expose.class);
+            return annotation != null && !annotation.serialize();
+        });
+
+        //Take the property name from the GSON SerializedName declaration
+        builder.forFields().withPropertyNameOverrideResolver(
+                field -> Optional.ofNullable(field.getAnnotationConsideringFieldAndGetter(SerializedName.class))
+                        .map(SerializedName::value).orElse(null));
+    }
+}

jsonschema-module-gson/src/test/java/com/github/victools/jsonschema/module/gson/IntegrationTest.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2020 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.module.gson;
+
+import com.fasterxml.jackson.annotation.JsonClassDescription;
+import com.fasterxml.jackson.annotation.JsonIdentityInfo;
+import com.fasterxml.jackson.annotation.JsonIdentityReference;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonPropertyDescription;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonUnwrapped;
+import com.fasterxml.jackson.annotation.JsonValue;
+import com.fasterxml.jackson.annotation.ObjectIdGenerators;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.victools.jsonschema.generator.Option;
+import com.github.victools.jsonschema.generator.OptionPreset;
+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 java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Scanner;
+
+import com.google.gson.annotations.SerializedName;
+import org.junit.jupiter.api.Test;
+import org.skyscreamer.jsonassert.JSONAssert;
+import org.skyscreamer.jsonassert.JSONCompareMode;
+
+/**
+ * Integration test of this module being used in a real SchemaGenerator instance.
+ */
+public class IntegrationTest {
+
+    @Test
+    public void testIntegration() throws Exception {
+        GsonModule module = new GsonModule();
+        SchemaGeneratorConfig config = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_7, OptionPreset.PLAIN_JSON)
+                .with(Option.DEFINITIONS_FOR_MEMBER_SUPERTYPES, Option.NULLABLE_ARRAY_ITEMS_ALLOWED)
+                .with(Option.NONSTATIC_NONVOID_NONGETTER_METHODS, Option.FIELDS_DERIVED_FROM_ARGUMENTFREE_METHODS)
+                .with(module)
+                .build();
+        SchemaGenerator generator = new SchemaGenerator(config);
+        JsonNode result = generator.generateSchema(TestClass.class);
+
+        String rawJsonSchema = result.toString();
+        System.out.println(rawJsonSchema);
+        JSONAssert.assertEquals('\n' + rawJsonSchema + '\n',
+                loadResource("integration-test-result.json"), rawJsonSchema, JSONCompareMode.STRICT);
+    }
+
+    private static String loadResource(String resourcePath) throws IOException {
+        StringBuilder stringBuilder = new StringBuilder();
+        try (InputStream inputStream = IntegrationTest.class
+                .getResourceAsStream(resourcePath);
+                Scanner scanner = new Scanner(inputStream, StandardCharsets.UTF_8.name())) {
+            while (scanner.hasNext()) {
+                stringBuilder.append(scanner.nextLine()).append('\n');
+            }
+        }
+        return stringBuilder.toString();
+    }
+
+    static class TestClass {
+
+        @SerializedName(value = "field_with_overridden_name")
+        public boolean originalFieldName;
+
+        public TestEnum enumValueHandledByStandardOption;
+
+    }
+
+    enum TestEnum {
+        A, B, C
+    }
+
+}

jsonschema-module-gson/src/test/resources/com/github/victools/jsonschema/module/gson/integration-test-result.json

@@ -0,0 +1,17 @@
+{
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "type": "object",
+    "properties": {
+        "enumValueHandledByStandardOption": {
+            "type": "string",
+            "enum": [
+                "A",
+                "B",
+                "C"
+            ]
+        },
+        "field_with_overridden_name": {
+            "type": "boolean"
+        }
+    }
+}

jsonschema-module-gson/src/test/resources/logback.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="warn">
+        <appender-ref ref="console"/>
+    </root>
+</configuration>

pom.xml

@@ -19,6 +19,7 @@
                 <module>jsonschema-generator-bom</module>
                 <module>jsonschema-generator-parent</module>
                 <module>jsonschema-generator</module>
+                <module>jsonschema-module-gson</module>
                 <module>jsonschema-module-jackson</module>
                 <module>jsonschema-module-jakarta-validation</module>
                 <module>jsonschema-module-javax-validation</module>