fix string compare in haskell generator (#18410)

Author: wing328

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

@@ -333,13 +333,14 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
 
     /**
      * Internal method to set the generateToSchema parameter.
-     *
+     * <p>
      * Basically we're generating ToSchema instances (generically) for all schemas.
      * However, if any of the contained datatypes doesn't have the ToSchema instance,
      * we cannot generate it for its "ancestor" type.
      * This is the case with the "Data.Aeson.Value" type: it doesn't (and cannot) have
      * a Swagger-compatible ToSchema instance. So we have to detect its presence "downstream"
      * the current schema, and if we find it we just don't generate any ToSchema instance.
+     *
      * @param model
      */
     private void setGenerateToSchema(CodegenModel model) {
@@ -356,7 +357,7 @@ private void setGenerateToSchema(CodegenModel model) {
 
         List<CodegenModel> children = model.getChildren();
         if (children != null) {
-            for(CodegenModel child : children) {
+            for (CodegenModel child : children) {
                 setGenerateToSchema(child);
             }
         }
@@ -512,7 +513,7 @@ public CodegenOperation fromOperation(String resourcePath, String httpMethod, Op
         // Query parameters appended to routes
         for (CodegenParameter param : op.queryParams) {
             String paramType = param.dataType;
-            if (param.contentType == "application/json") {
+            if ("application/json".equals(param.contentType)) {
                 if (param.isArray) {
                     paramType = "[JSONQueryParam " + paramType.substring(1, paramType.length() - 1) + "]";
                 } else {
@@ -554,7 +555,7 @@ public CodegenOperation fromOperation(String resourcePath, String httpMethod, Op
             path.add("Header \"" + param.baseName + "\" " + param.dataType);
 
             String paramType = param.dataType;
-            if (param.contentType == "application/json") {
+            if ("application/json".equals(param.contentType)) {
                 if (param.isArray) {
                     paramType = "(JSONQueryParam " + paramType.substring(1, paramType.length() - 1) + ")";
                 } else {
@@ -721,5 +722,7 @@ public void postProcessFile(File file, String fileType) {
     }
 
     @Override
-    public GeneratorLanguage generatorLanguage() { return GeneratorLanguage.HASKELL; }
+    public GeneratorLanguage generatorLanguage() {
+        return GeneratorLanguage.HASKELL;
+    }
 }