Spring rest2ts generator

spring-rest2ts-generator generates TypeScript code based on Spring MVC REST controllers and data model for HTTP requests and responses.

spring-rest2ts-generator started from Spring MVC but we noticed that it is easy to support also JAX-RS annotations and such support has been added in version 1.2.4. For model conversion Jackson or Gson annotations could be used.

In version 1.4.0 there is added support for jackson-js library which allows to deserialize JSON to ES6 classes which gives possibility to use in the model types which are missing in the JSON like Date, Map, Set and in the code we can use intanceof operator on instances. Details are in the paragraph Jackon-js conversion listener

Features

From model classes there are generated TypeScript interfaces and from REST controllers full working Angular services based on Observable API or plain JavaScript services based on Promises API. The main idea is that Spring annotations describing REST endpoints have enough information to compose HTTP request and call REST endpoints so TypeScript code could be automatically generated. Code created by typescript generator reduces the amount of handwritten code on the frontend and gives type-safe API to the backend, changes in URL path are hidden, in case of REST endpoint refactoring, generated code will reflect these changes which will avoid compile-time error in the web app which reduces time on testing

Supported features:

• Java Beans convention for data model mapping
• FasterXML/Jackson annotations for data model mapping
• Custom type Mappings
• Java collections mapped into TS arrays
• Java Map mapped into TS object
• Java packages to module conversion
• Java enums mapped as TS enums or union types
• Inheritance mapping
• Name mappings
• Imports between generated TS modules
• Spring REST annotations based on which TS services are generated
• TS services for Angular framework
• TS services for ReactJS framework
• Java class filtering for TS code generation
• Java generic types mapped to TS generics : since ver 1.2.2
• Java interfaces implemented by model classes which contains getters and setter are mapped to TS interfaces to have common types to different TS model classes : since ver 1.2.2
• spring data support (Pageable & Page types) : since ver 1.2.2
• JAX-RS annotation support : since ver 1.2.4
• model converter which generates TypeScript classes aligned with angular2-jsonapi library
• model serializers extension which allows to configure custom JSON serializers/deserializers : since ver 1.2.6
• Gson serializer support since version 1.3.0
• jackson-js support since version 1.4.0
• Spring WebFlux types (Mono and Flux) support since version 1.5.0

Installation

To add a dependency on spring-rest2ts-generator using Maven, use the following:

<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-generator</artifactId>
    <version>1.5.1</version>
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-spring</artifactId>
    <version>1.5.1</version>
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-spring-data</artifactId>
    <version>1.5.1</version>
    <!-- only if spring data is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-jackson</artifactId>
    <version>1.5.1</version>
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-jax-rs</artifactId>
    <version>1.5.1</version>
    <!-- only if JAX-RS is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-angular2json-impl</artifactId>
    <version>1.5.1</version>
    <!-- only if angular2json is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-gson</artifactId>
    <version>1.5.1</version>
    <!-- only if Gson is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-jackson-js</artifactId>
    <version>1.5.1</version>
    <!-- only if jackson-js is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-webflux</artifactId>
    <version>1.5.1</version>
    <!-- only if webflux is used-->
</dependency>

Configuration

Due to greater flexibility typescript generator is configured by code, no configuration files are needed. This gives possibility to easily extend generator in places where it is needed Here is the simplest generator configurator:

    Rest2tsGenerator tsGenerator = new Rest2tsGenerator();
    
    // Java Classes filtering
    tsGenerator.setModelClassesCondition(new ExtendsJavaTypeFilter(BaseDTO.class));
    tsGenerator.setRestClassesCondition(new ExtendsJavaTypeFilter(BaseCtrl.class));
    
    // Java model classes converter setup
    JacksonObjectMapper jacksonObjectMapper = new JacksonObjectMapper();
    jacksonObjectMapper.setFieldsVisibility(JsonAutoDetect.Visibility.ANY);
    modelClassesConverter = new ModelClassesToTsInterfacesConverter(jacksonObjectMapper);
    tsGenerator.setModelClassesConverter(modelClassesConverter);
    
    // Spring REST controllers converter
    restClassesConverter = new SpringRestToTsConverter(new Angular4ImplementationGenerator());
    tsGenerator.setRestClassesConverter(restClassesConverter);
    
    // set of java root packages for class scanning
    javaPackageSet = Collections.singleton("com.blueveery.springrest2ts.examples");
    tsGenerator.generate(javaPackageSet, Paths.get("../target/ts-code"));

Examples

Model classes:

public class BaseDTO {
    private int id;
    @JsonFormat(shape = JsonFormat.Shape.NUMBER)
    private Date updateTimeStamp;
}

public class OrderDTO extends BaseDTO {
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd-MM-yyyy hh:mm:ss")
    private LocalDateTime orderTimestamp;
}

Spring REST controller:

@Controller
@RequestMapping("api/order")
public class OrderCtrl {

    @PostMapping(consumes = {"application/json"}, produces = {"application/json"})
    @ResponseBody
    @ResponseStatus(HttpStatus.CREATED)
    public OrderDTO createOrder(@RequestBody OrderDTO entity) {
        return entity;
    }

    @RequestMapping(path = "/{id}", method = RequestMethod.GET, produces = {"application/json"})
    @ResponseBody
    public OrderDTO getOrder(@PathVariable int id) {
        return new OrderDTO();
    }

}

Output

Typescript model class:

export interface Base {
    id: number;
    updateTimeStamp: number;
}


export interface Order extends Base {
    /**
     *    pattern : dd-MM-yyyy hh:mm:ss
     */
    orderTimestamp: string;
}

Observable based service:

@Injectable()
export class OrderService {
    httpService: HttpClient;


    public constructor(httpService: HttpClient) {
        this.httpService = httpService;
    }

    public createOrder(entity: Order): Observable<Order> {
        let headers = new HttpHeaders().set('Content-type', 'application/json');
        return this.httpService.post<Order>('api/order', entity, {headers});
    }

    public getOrder(id: number): Observable<Order> {
        return this.httpService.get<Order>('api/order/' + id + '');
    }
    
}

Promise based service:

export class OrderService {
    baseURL: URL;


    public constructor(baseURL: URL = new URL(window.document.URL)) {
        this.baseURL = baseURL;
    }

    public createOrder(entity: Order): Promise<Order> {
        const url = new URL('/api/order', this.baseURL);

        return fetch(url.toString(), {
            method: 'POST',
            headers: {'Content-Type': 'application/json'},
            body: JSON.stringify(entity)
        }).then(res => res.json());
    }

    public getOrder(id: number): Promise<Order> {
        const url = new URL('/api/order/' + id + '', this.baseURL);

        return fetch(url.toString(), {method: 'GET'}).then(res => res.json());
    }

}

Module spring-rest2ts-examples contains few model classes and REST controllers, class TsCodeGenerationsTest and ExtendedTsCodeGenerationsTest contains few ready to run configuration examples (they are not unit tests, just examples), each example generates code to directory target/classes/test-webapp/src, its parent directory target/classes/test-webapp contains webpack and npm setup which is valid for all generator configurations apart from configurableTsModulesConverter which has different entry points due to changed module names. To compile generated TypeScript code just execute following commands in folder target/classes/test-webapp:

    npm install
    npm run build
    

or just review generated code in Your favourite IDE which supports TypeScript

Basic Configuration

Java Classes filtering

Generator needs two filters to select java classes for which TypeScript types will be generated, these filters allows to skip Java classes in given packages for which TypeScript generation is not needed. By default Rest2tsGenerator for model classes and rest controllers has RejectJavaTypeFilter which rejects all classes in a given java packages. Such filter could be used to skip generation for REST controllers when only Typescript types are needed for Java model classes. There are following filters which allows to build complex conditions:

• ExtendsJavaTypeFilter
• HasAnnotationJavaTypeFilter
• JavaTypePackageFilter
• ContainsSubStringJavaTypeFilter
• RegexpJavaTypeFilter
• RejectJavaTypeFilter
• OrFilterOperator
• AndFilterOperator
• NotJavaTypeFilter

Java model classes converter

Java classes which describe payload model are generated to TypeScript interfaces. Java collections are converted into JavaScript arrays, Java Map is converted into object where key has a string type and value is converted Typescript Type During model serialization to JSON, object mapper is applying some mappings(some of them are required for example in the JSON, Date type must be represented as string or number) based on some default configuration or dedicated annotations. Currently, Jackson Object mapper and Gson Object mapper are supported.

Jackson Object mapper

JacksonObjectMapper allows to set fields, getters and setters visibility. Based on this Typescript interface fields are generated. Following Jackson annotations are supported :

• JsonTypeInfo - TS property is added if type info is serialized to property
• JsonAutoDetect - overrides default visibility
• JsonIgnoreType - properties which have type marked as ignored are skipped
• JsonIgnoreProperties - ignores listed properties
• JsonIgnore - ignores marked property
• JsonBackReference - ignores TS property
• JsonProperty - changes property name, based on access marks TS property as readonly
• JsonSetter - changes property name
• JsonGetter - changes property name
• JsonUnwrapped - add fields from property type to the current TS interface
• JsonValue
• JsonFormat - changes TS property type, add to TS comment pattern if given
• JacksonInject - marks TS property as readonly
• JsonRawValue - changes TS property type to any

Gson Object mapper

Following Gson annotations are supported:

• Expose - when used with exluder.excludeFieldsWithoutExposeAnnotation() only fields with this annotation are added to Typescript
• Since - when used with exluder..withVersion(...) only fields witch matches version are added to Typescript, there is also added comment to Typescript field
• Until - when used with exluder..withVersion(...) only fields witch matches version are added to Typescript, there is also added comment to Typescript field
• SerializedName - changes field name in Typescript type

Gson object mapper is configured by Gson excluder so it gives all possibilities to filter classes and fields given by gson excluder. Mapper can be also configured with FieldNamingStrategy to change fields names. In Gson there is a problem with @JsonAdapter which could changes completely how object looks after serialization. This problem could be divided in two cases:

• when complex type is changed into primitive one for Example Date into number, such case could be solved by Custom type mapping When custom type naming is defined Java class is not converted into typescript type
• when complex type is converted into Typescript type with some modifications, in that case do not define Custom type mapping, normal conversion will be applied and register Conversion Listener to modify class as it is required

Gson doesn't support natively polymorphic types, in such case in root class there is required an additional field which will be a type denominator, such field could be also added by Conversion Listener To use Gson Object mapper you need to pass it to modelClassesConverter in the configuration

Spring REST controllers converter

From REST classes there is generated working implementation in TypeScript which based on Spring annotations builds complete HTTP request. Such implementation depends also used JavaScript framework, there is different approach to HTTP calls in Angular and React so SpringRestToTsConverter requires instance of ImplementationGenerator. There are available two such implementation generators

• Angular4ImplementationGenerator - generates valid Angular services with methods which corresponds to REST endpoints, they have wrapped return type into Observable
• FetchBasedImplementationGenerator - generates valid plain JavaScript classes with methods which corresponds to REST endpoints, return types are mapped into Promise where it generic type attribute is endpoint return type

There are supported following Spring annotations:

• RequestMapping
• GetMapping
• PostMapping
• PutMapping
• DeleteMapping
• PatchMapping
• PathVariable
• RequestParam
• RequestBody

Support for spring data in Spring REST controllers - since ver 1.2.2

Parameters with type 'Pageable' from spring data, now are supported by adding extension to spring converter:

    restClassesConverter.getConversionExtensionList().add(new SpringDataRestConversionExtension());

Data from pageable are sent to server and server response with Page object which contains Pageable, fields which can be set on client side are not readonly, namely:

export interface Pageable {
    pageNumber: number;
    pageSize: number;
    sort?: Sort;
    readonly paged?: boolean;
    readonly offset?: number;
    readonly unpaged?: boolean;
}

before REST method call in Pageable object pageNumber and pageSize must be set and optionally sort. Others fields are calculated on the server and sent back to client in Page object

If parameter with type Pageable is marked with annotation @PageableDefault, parameter in TypeScript is optional

Spring WebFlux Support - since ver 1.5.0

To generate typescript code from reactive REST controllers, apart from other configuration required for controllers you need to use WebFluxConfigurator in the following way:

    WebFluxConfigurator.configure(tsGenerator);

With such configuration Mono type is unpacked and type parameter for Mono is used as return type: Mono<Product> is converted to Product Flux type is converted into array where item type is taken from Flux type parameter: Flux<Product> is converted to Product[]

JaX-RS REST controllers converter - since ver 1.2.4

Since version 1.2.4 there is provided JaxRsRestToTsConverter which converts JAX-RS controllers into TypeScript services. It supports following JAX-RS annotations:

• @GET
• @POST
• @PUT
• @DELETE
• @PATCH
• @Path
• @Produces
• @Consumes
• @PathParam
• @DefaultValue

JaxRsRestToTsConverter converter can be used with existing implementation generators Angular4ImplementationGenerator and FetchBasedImplementationGenerator so code could be generated for Angular as well as for frameworks where Promises are used. JaxRsRestToTsConverter usage example:

    ClassNameMapper classNameMapper = new SubstringClassNameMapper("ResourceImpl", "Service");
    JaxRsRestToTsConverter jaxRsRestToTsConverter = new JaxRsRestToTsConverter(new Angular4ImplementationGenerator(), classNameMapper);
    tsGenerator.setRestClassesConverter(jaxRsRestToTsConverter);

Class JaxRsGenerationTest contains examples how to generate TypeScript code from JAX-RS REST endpoints

Jackon-js conversion listener - since ver 1.4.0

jackson-js library which allows to deserialize JSON to ES6 classes which gives possibility to use in the model types, which are missing in the JSON like Date, Map, Set. In the code we can also use intanceof operator on instances. This conversion is based on the following classes:

• ModelClassesToTsClassesConverter which converts Java classes to Typescript classes
• JacksonAnnotationsConversionToJacksonJs it is conversion listener which extends conversion made by ModelClassesToTsClassesConverter and adds jackson-js decorators based on the Java types and Jackson annotations
• JacksonJsModelSerializerExtension adds in REST services calls to objectMapper to serialize/deserialize objects

Class com/blueveery/springrest2ts/examples/test/JacksonJSTest has example how to configure generator for code generation compatible with jackon-js library. Current conversion supports following decorators:

• @JsonTypeInfo, @JsonSubTypes, @JsonTypeName to allows jackosn-js deserialize polymorphic collections and fields
• @JsonClassType and @JsonProperty() on fields with proper metadata which allows jackosn-js library to deserialize JSON to ES6 class instances

Inheritance support

Type name conversion is supported for following settings on The Java side:

• JsonTypeInfo.Id.NAME in that case there is required implementation of typeIdResolver which gets on input current class and inheritance root class and produces class name
• JsonTypeInfo.Id.CLASS for decorators @JsonSubTypes, @JsonTypeName there is used full Java class name
• JsonTypeInfo.Id.MINIMAL_CLASS for decorators @JsonSubTypes, @JsonTypeName there is used minimal Java class name

For Java JsonTypeInfo.include() following settings how to include in the JSON type info are supported:

• PROPERTY & EXISTING_PROPERTY mapped to PROPERTY
• WRAPPER_OBJECT mapped to WRAPPER_OBJECT
• WRAPPER_ARRAY mapped to WRAPPER_ARRAY

Classes in one inheritance hierarchy must be mapped to the same TS module because derived types are used on the top level class in JacksonJs decorators, which will cause circular dependencies between modules but the same problem will be at the backend with packages.

Custom type mapping for class hierarchy

Having possibility to map JSON to real ES6 class instances, tsGenerator has new mapping customTypeMappingForClassHierarchy which allows to map Java class and all derived classes to specified TypeScript class. It makes sens mainly for collections. If we want to say that all fields which has type Set or type which implements this interface should be mapped to JS Set we can add following mappings:

        tsGenerator.getCustomTypeMappingForClassHierarchy().put(Map.class, TypeMapper.tsMap);
        tsGenerator.getCustomTypeMappingForClassHierarchy().put(Collection.class, TypeMapper.tsArrayCollection);
        tsGenerator.getCustomTypeMappingForClassHierarchy().put(Set.class, TypeMapper.tsSet);
        tsGenerator.getCustomTypeMappingForClassHierarchy().put(Date.class, TypeMapper.tsDate);

Settings above will map all Java

• maps to JS Map
• collection to JS Array class
• sets to JS Set
• date and inherited types to JS Date in case where Java inheritance trees overlaps like for Collection and Set the nearest Java type is selected so in this case HashSet will be mapped to JS Set not to Array

JS Date is supported if it is serialized to number, the same is for Enums. To add support for other JacksonJS decorators, users could create own conversion listener and add it together with JacksonAnnotationsConversionToJacksonJs to model converter. In JacksonAnnotationsConversionToJacksonJs we tried to add only the most basic JacksonJs decorators.

We must add that `jackson-js` is not actively supported at this moment, but it is the best library for this purpose which we were able to find. Maybe if there will be interested in this solution we will find contributor which will keep this library up to date. Having classes and decorators at the TypeScript side will open possibilities for integration with many others libraries, feedback if this is desired direction is welcome.

Java model classes to angular2-json-api converter - since ver 1.2.4

angular2-jsonapi is an TypeScript library which converts in web application incoming JSON into classes and classes into JSON. Given advantage is that TypeScript interfaces doesn't exists in runtime in opposite to classes but to use classes, conversion is required which is done by angular2-jsonapi library, to enable this conversions some TypeScript decorators are required on generated TypeScript model classes. There is provided java model classes converter ModelClassesToTsAngular2JsonApiConverter which adds following TypeScript decorators

• JsonApiModelConfig - class level decorator
• Attribute - set for simple fields
• HasMany - set for collections
• BelongsTo - set for fields with type which is model class

First TypeScript class in the inheritance root has set base class to TypeScript JsonApiModel as it is required by angular2-jsonapi library

JsonApiModelConfig decorator has parameter type which is type name, this field is generated from TypeScript class name (name.toLowerCase()+"s") or is taken from Java annotation JsonApiModelConfig. To customize type name, Java model class must be annotated with JsonApiModelConfig annotation which is provided by module

    <dependency>
        <groupId>com.blue-veery</groupId>
        <artifactId>spring-rest2ts-angular2json-api</artifactId>
        <version>1.5.1</version>
    </dependency>

which needs to be included in Java project. Simple configuration:

//set model class converter
    JacksonObjectMapper jacksonObjectMapper = new JacksonObjectMapper();
    jacksonObjectMapper.setFieldsVisibility(JsonAutoDetect.Visibility.ANY);
    ModelClassesToTsAngular2JsonApiConverter modelClassesConverter = new ModelClassesToTsAngular2JsonApiConverter(jacksonObjectMapper);
    tsGenerator.setModelClassesConverter(modelClassesConverter);

ModelClassesToTsAngular2JsonApiConverter has also ability to generate model variable which is a mapping from type name to TypeScript class, this mapping is required by angular2-jsonapi configuration object. To have such config generated, generator configuration needs to create such variable,

    ModelClassesToTsAngular2JsonApiConverter modelClassesConverter = new ModelClassesToTsAngular2JsonApiConverter(jacksonObjectMapper);
    //models variable is optional, if not set it will not be generated, module selection is up to user decision
    JavaPackageToTsModuleConverter javaPackageToTsModuleConverter = tsGenerator.getJavaPackageToTsModuleConverter();
    //there is selected TypeScript module where there will be generated class for ManufacturerDTO.class
    TSModule tsModuleForModelsVariable = javaPackageToTsModuleConverter.getTsModule(ManufacturerDTO.class);
    JavaPackageToTsModuleConverter javaPackageToTsModuleConverter = tsGenerator.getJavaPackageToTsModuleConverter();
    TSModule tsModuleForModelsVariable = javaPackageToTsModuleConverter.getTsModule(ManufacturerDTO.class);
    modelClassesConverter.createModelsVariable("models", tsModuleForModelsVariable);
    tsGenerator.setModelClassesConverter(modelClassesConverter);

Configuration examples are in class Angular2JsonApiTest

This converter is an experimental version, generated code could contain some inconsistencies since we weren't able to find rules how to apply angular2-jsonapi decorators to fields, only examples, base on which incorrect conclusions could be made!

Response content conversion

• If REST endpoint produces JSON generated service method returns Observable or Promise<<Mapped java type>>
• If REST endpoint doesn't produce response it should return response code 204(no content) generated service method returns Observable or Promise<void>
• If REST endpoint returns java primitive types like string, numbers or booleans there is made conversion to proper JavaScript type, for such REST endpoint required content type is text.

Final step in generator configuration

Generator takes as input set of java packages which should be scanned for java classes and output path where TypesScript modules will be generated. There are required only root packages in case if following packages are present:

• com.blueveery.springrest2ts.examples.models
• com.blueveery.springrest2ts.examples.ctrls it is is enough to list package com.blueveery.springrest2ts.examples.ctrls. Generator discovers also nested classes, if model classes or REST controllers are using such classes, adequate TypeScript classes/interfaces will be generated

Advanced configuration

Modules converters

Modules converter defines, in which TypeScript module, should be placed generated TypeScript type for given Java class There are two types of modules converters:

• TsModuleCreatorConverter
• ConfigurableTsModulesConverter

TsModuleCreatorConverter

By default generator is using TsModuleCreatorConverter, this converter takes a few last subpackages from java package and joins them using hyphen. For java package com.blueveery.springrest2ts.examples.ctrls it will create TS module examples-ctrls if this converter is configured to use last two subpackages. This converter will create module for any found java class.

    TsModuleCreatorConverter moduleConverter = new TsModuleCreatorConverter(3); // use three last subpackges
    tsGenerator.setJavaPackageToTsModuleConverter(moduleConverter); 

Imports between generated types are using path from root so in tsconfig.json, in the web project, in which generated code is used, baseUrl must be defined as it is in examples.

ConfigurableTsModulesConverter

ConfigurableTsModulesConverter takes as an input maping from java packages to typeScript module which allows to specify name of each generated module. This generator optionally as an input takes also TsModuleCreatorConverter to generate modules for packages which are missing in the mapping

    HashMap<String, TSModule> packagesMap = new HashMap<>();
    packagesMap.put("com.blueveery.springrest2ts.examples.model", new TSModule("model", Paths.get("app/sdk/model"), false));
    TSModule servicesModule = new TSModule("services", Paths.get("app/sdk/services"), false);
    packagesMap.put("com.blueveery.springrest2ts.examples.ctrls.core", servicesModule);
    packagesMap.put("com.blueveery.springrest2ts.examples.ctrls", servicesModule);
    ConfigurableTsModulesConverter moduleConverter = new ConfigurableTsModulesConverter(packagesMap);
    tsGenerator.setJavaPackageToTsModuleConverter(moduleConverter);

Enums converters

Java enums could be serialized as strings or ordinals. If they are serialized to strings in TypesScript union of enum values could be used, if enums are serialized to ordinals TypesScript enums could be generated. To handle this there are provided two enums converters

• JavaEnumToTsUnionConverter
• JavaEnumToTsEnumConverter

and configured in code:

    tsGenerator.setEnumConverter(new JavaEnumToTsUnionConverter());

or

    tsGenerator.setEnumConverter(new JavaEnumToTsEnumConverter());

Type names mapping

Between Java and TypeScript there are different naming conventions for example model classes could end with postfix "DTO" which could be unwanted in generated Typescript model, REST controllers could have "Ctrl" postfix where generated Angular services should have postfix "Service". To handle this situation type name mappers are provided. Currently there is only one implementation SubstringClassNameMapper but any one could crete new one by implementing interface 'ClassNameMapper' Each class converter is using name mapper so they can be defined for enum, model and REST classes

    modelClassesConverter.setClassNameMapper(new SubstringClassNameMapper("DTO", ""));
    restClassesConverter.setClassNameMapper(new SubstringClassNameMapper("Ctrl", "Service"));

Custom type mapping

During serialization some types are converted by default, such conversion does not depends on any annotations to learn how convert types. For example UUID could be converted to string, Date to number or string/array of numbers. To handle such situation generator has map of custom mapping which allows to define such new mappings:

    tsGenerator.getCustomTypeMapping().put(UUID.class, TypeMapper.tsString);
    tsGenerator.getCustomTypeMapping().put(BigInteger.class, TypeMapper.tsNumber);
    tsGenerator.getCustomTypeMapping().put(LocalDateTime.class, TypeMapper.tsNumber);
    tsGenerator.getCustomTypeMapping().put(LocalDate.class, new TSArray(TypeMapper.tsNumber));

Class TypeMapper has static fields for all base TypeScript types, and for other cases types could be created using TS model like for array of numbers new TSArray(TypeMapper.tsNumber)

Model serializers extensions : since ver 1.2.6

Since ver 1.2.6 there is a possibility to use a custom JSON serializers/deserializers in generated code. By default, there is used StandardJsonSerializerExtension which is generating code based on standard JavaScript JSON object (JSON.stringify & JSON.parse). Json5ModelSerializerExtension extension allows to use JSON5 serializer. Following code snippet is showing how to configure generator:

    ImplementationGenerator implementationGenerator = new Angular4ImplementationGenerator();
    implementationGenerator.setSerializationExtension(new Json5ModelSerializerExtension());
    restClassesConverter = new SpringRestToTsConverter(implementationGenerator);
    tsGenerator.setRestClassesConverter(restClassesConverter);

    tsGenerator.generate(javaPackageSet, OUTPUT_DIR_PATH);

To provide own JSON serializers/deserializers extension, user should implement ModelSerializerExtension interface

Nullable types

TypeScript has s great feature to warn about cases where value could be null. To use it TS compiler option must be set strictNullChecks and proper fields in model set as nullable or proper parameters in methods which make REST calls. Generators support this by marking TS fields based on information taken from corresponding java classes. Generator is using NullableTypesStrategy with default implementation DefaultNullableTypesStrategy which marks types as nullable if

• field or method parameter type is wrapped in Java java.util.Optional
• field or method parameter is marked with annotation javax.annotation.Nullable
• field or method parameter has type which is Java wrapper for primitive types

Marks mean that field type is union of original field type and null;

DefaultNullableTypesStrategy has settings which allows to configure which of above option use, by default all they are used

    DefaultNullableTypesStrategy nullableTypesStrategy = new DefaultNullableTypesStrategy();
    nullableTypesStrategy.setUsePrimitiveTypesWrappers(false);
    tsGenerator.setNullableTypesStrategy(nullableTypesStrategy);

Conversion Listeners

Each converter( enum, model classes, rest classes) allows for registering conversion listeners, such listeners give possibility to extend conversion with new functionality. Now there is one, such listener provided SwaggerConversionListener which adds comments to TypeScript types based on swagger 2.0 io.swagger.oas.annotations.Operation annotation

    restClassesConverter.getConversionListener().getConversionListenerSet().add(new SwaggerConversionListener());

TypeScript code formatting

Generated TypeScript code is not formatted. Code formatting from project to project could have totally different requirements and it is suggested to use dedicated formatting library for this purpose like:

• prettier.io
• typescript-formatter

Java compiler setup

Java compiler by default optimizes methods parameters names, to have readable parameters names in Typescript at least for REST controllers modules this optimization should be switched off

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <compilerArgs>
                    <compilerArg>-parameters</compilerArg>
                </compilerArgs>
            </configuration>
        </plugin>

Some special cases

Model class getter and setter types differs

In most cases such situation is just a bug but there could be a situations in which this is required to handle TypeScript field as an union of getter and setter type, in this order. Special case of this situation is when getter or setter is missing. For missing setter field in TypeScript it is marked as readonly. For missing getter (for example we send password but do not read them from server) TypeScript field is union of undefined | <setter type> because after read from server such fields will have value of undefined

Java REST controllers overloaded methods

Java allows for overloaded methods what is not supported by TypeScript/JavaScript. To solve this problems if overloaded methods are met in REST controller, generated method names in TypeScript are changed by appending in first round HTTP methods to TypeScript method name if they differ, if not URL path is appended splitted on / and joined with _

Angular compilation issue for ambient modules d.ts

Angular for modules with typings, reports an error : Module not found: Error: Can't resolve <module path> We think that it is reported bug: angular/angular-cli#4874 tsc compilation for generated modules works fine. To overcome this problem generator by default, generates only normal modules *.ts. To generate ambient modules following option must be set:

Rest2tsGenerator.generateAmbientModules = true; 

Unsupported mappings, coming soon...

• multipart mapping RequestPart