Revise how to obtain the example value

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -25,10 +25,7 @@
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.Operation;
 import io.swagger.v3.oas.models.headers.Header;
-import io.swagger.v3.oas.models.media.ArraySchema;
-import io.swagger.v3.oas.models.media.ComposedSchema;
-import io.swagger.v3.oas.models.media.Schema;
-import io.swagger.v3.oas.models.media.StringSchema;
+import io.swagger.v3.oas.models.media.*;
 import io.swagger.v3.oas.models.parameters.CookieParameter;
 import io.swagger.v3.oas.models.parameters.HeaderParameter;
 import io.swagger.v3.oas.models.parameters.Parameter;
@@ -1083,6 +1080,50 @@ public void setParameterExampleValue(CodegenParameter codegenParameter) {
 
     }
 
+    /**
+     * Return the example value of the parameter.
+     *
+     * @param codegenParameter Codegen parameter
+     * @param parameter Parameter
+     */
+    public void setParameterExampleValue(CodegenParameter codegenParameter, Parameter parameter) {
+        if (parameter.getExample() != null) {
+            codegenParameter.example = parameter.getExample().toString();
+            return;
+        }
+
+        Schema schema = parameter.getSchema();
+        if (schema != null && schema.getExample() != null) {
+            codegenParameter.example = schema.getExample().toString();
+            return;
+        }
+
+        setParameterExampleValue(codegenParameter);
+    }
+
+    /**
+     * Return the example value of the parameter.
+     *
+     * @param codegenParameter Codegen parameter
+     * @param requestBody Request body
+     */
+    public void setParameterExampleValue(CodegenParameter codegenParameter, RequestBody requestBody) {
+        Content content = requestBody.getContent();
+
+        if (content.size() > 1) {
+            // @see ModelUtils.getSchemaFromContent()
+            LOGGER.warn("Multiple MediaTypes found, using only the first one");
+        }
+
+        MediaType mediaType = content.values().iterator().next();
+        if (mediaType.getExample() != null) {
+            codegenParameter.example = mediaType.getExample().toString();
+            return;
+        }
+
+        setParameterExampleValue(codegenParameter);
+    }
+
     /**
      * Return the example value of the property
      *
@@ -2719,7 +2760,7 @@ public CodegenParameter fromParameter(Parameter parameter, Set<String> imports)
 
         // set the parameter excample value
         // should be overridden by lang codegen
-        setParameterExampleValue(codegenParameter);
+        setParameterExampleValue(codegenParameter, parameter);
 
         postProcessParameter(codegenParameter);
         LOGGER.debug("debugging codegenParameter return: " + codegenParameter);
@@ -4328,7 +4369,7 @@ public CodegenParameter fromRequestBody(RequestBody body, Map<String, Schema> sc
 
         // set the parameter's example value
         // should be overridden by lang codegen
-        setParameterExampleValue(codegenParameter);
+        setParameterExampleValue(codegenParameter, body);
 
         return codegenParameter;
     }

modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java

@@ -233,6 +233,54 @@ public void updateCodegenPropertyEnum() {
         Assert.assertEquals(testedEnumVar.getOrDefault("isString", ""), false);
     }
 
+    @Test
+    public void testExample1() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/examples.yaml", null, new ParseOptions()).getOpenAPI();
+        final DefaultCodegen codegen = new DefaultCodegen();
+
+        Operation operation = openAPI.getPaths().get("/example1").getGet();
+        CodegenParameter codegenParameter = CodegenModelFactory.newInstance(CodegenModelType.PARAMETER);
+        codegen.setParameterExampleValue(codegenParameter, operation.getParameters().get(0));
+
+        Assert.assertEquals(codegenParameter.example, "example1 value");
+    }
+
+    @Test
+    public void testExample2() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/examples.yaml", null, new ParseOptions()).getOpenAPI();
+        final DefaultCodegen codegen = new DefaultCodegen();
+
+        Operation operation = openAPI.getPaths().get("/example2").getGet();
+        CodegenParameter codegenParameter = CodegenModelFactory.newInstance(CodegenModelType.PARAMETER);
+        codegen.setParameterExampleValue(codegenParameter, operation.getParameters().get(0));
+
+        Assert.assertEquals(codegenParameter.example, "example2 value");
+    }
+
+    @Test
+    public void testExample3() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/examples.yaml", null, new ParseOptions()).getOpenAPI();
+        final DefaultCodegen codegen = new DefaultCodegen();
+
+        Operation operation = openAPI.getPaths().get("/example3").getGet();
+        CodegenParameter codegenParameter = CodegenModelFactory.newInstance(CodegenModelType.PARAMETER);
+        codegen.setParameterExampleValue(codegenParameter, operation.getParameters().get(0));
+
+        Assert.assertEquals(codegenParameter.example, "example3: parameter value");
+    }
+
+    @Test
+    public void testExample4() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/examples.yaml", null, new ParseOptions()).getOpenAPI();
+        final DefaultCodegen codegen = new DefaultCodegen();
+
+        Operation operation = openAPI.getPaths().get("/example4").getGet();
+        CodegenParameter codegenParameter = CodegenModelFactory.newInstance(CodegenModelType.PARAMETER);
+        codegen.setParameterExampleValue(codegenParameter, operation.getRequestBody());
+
+        Assert.assertEquals(codegenParameter.example, "example4 value");
+    }
+
     private CodegenProperty codegenPropertyWithArrayOfIntegerValues() {
         CodegenProperty array = new CodegenProperty();
         final CodegenProperty items = new CodegenProperty();

modules/openapi-generator/src/test/resources/3_0/examples.yaml

@@ -0,0 +1,63 @@
+openapi: 3.0.0
+servers:
+  - url: 'http://petstore.swagger.io/v2'
+info:
+  version: 1.0.0
+  title: OpenAPI Petstore
+  license:
+    name: Apache-2.0
+    url: 'http://www.apache.org/licenses/LICENSE-2.0.html'
+paths:
+  /example1:
+    get:
+      operationId: example1Get
+      parameters:
+        - name: parameter
+          in: query
+          example: 'example1 value'
+          schema:
+            type: string
+      responses:
+        '200':
+          description: successful operation
+  /example2:
+    get:
+      operationId: example2Get
+      parameters:
+        - name: parameter
+          in: query
+          schema:
+            type: string
+            example: 'example2 value'
+      responses:
+        '200':
+          description: successful operation
+  /example3:
+    get:
+      operationId: example3Get
+      parameters:
+        - name: parameter
+          in: query
+          example: 'example3: parameter value'
+          schema:
+            type: string
+            example: 'example3: schema value'
+      responses:
+        '200':
+          description: successful operation
+  /example4:
+    get:
+      operationId: example4Get
+      requestBody:
+        content:
+          application/x-www-form-urlencoded:
+            schema:
+              type: object
+              properties:
+                name:
+                  type: string
+            example: 'example4 value'
+      responses:
+        '200':
+          description: successful operation
+