format date in codegen (#20516)

Author: Zemke

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

@@ -31,6 +31,7 @@
 import io.swagger.v3.oas.models.parameters.RequestBody;
 import io.swagger.v3.oas.models.servers.Server;
 import io.swagger.v3.parser.util.SchemaTypeUtil;
+import java.text.SimpleDateFormat;
 import lombok.Getter;
 import lombok.Setter;
 import org.apache.commons.io.FilenameUtils;
@@ -71,6 +72,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractJavaCodegen.class);
     private static final String ARTIFACT_VERSION_DEFAULT_VALUE = "1.0.0";
+    private static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd", Locale.ROOT);
 
     public static final String DEFAULT_LIBRARY = "<default>";
     public static final String DATE_LIBRARY = "dateLibrary";
@@ -1638,6 +1640,9 @@ public void setParameterExampleValue(CodegenParameter p) {
     @Override
     public String toExampleValue(Schema p) {
         if (p.getExample() != null) {
+            if (p.getExample() instanceof Date) {
+                return DATE_FORMAT.format(p.getExample());
+            }
             return escapeText(p.getExample().toString());
         } else {
             return null;

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

@@ -965,4 +965,11 @@ public void removeAnnotationsTest() {
         Assert.assertEquals(codegen.removeAnnotations("List<@Valid Pet>"), "List<Pet>");
     }
 
+    @Test(description = "test generated example values for string properties")
+    public void testGeneratedExampleValues() {
+        final OpenAPI openAPI = FLATTENED_SPEC.get("3_0/spring/date-time-parameter-types-for-testing");
+        codegen.setOpenAPI(openAPI);
+        DateSchema dateSchema = (DateSchema) openAPI.getPaths().get("/thingy/{date}").getPost().getParameters().get(0).getSchema();
+        Assert.assertTrue(codegen.escapeQuotationMark(codegen.toExampleValue(dateSchema)).matches("2021-01-01"));
+    }
 }