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

In version 1.2.4 we also added support for angular2-jsonapi which is a lightweight Angular2+ adapter for JSON API

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 diffrent 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

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>1.2.5</version>
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-spring</artifactId>
    <version>1.2.5</version>
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-spring-data</artifactId>
    <version>1.2.5</version>
    <!-- only if spring data is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-jackson</artifactId>
    <version>1.2.5</version>
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-jax-rs</artifactId>
    <version>1.2.5</version>
    <!-- only if JAX-RS is used-->
</dependency>
<dependency>
    <groupId>com.blue-veery</groupId>
    <artifactId>spring-rest2ts-angular2json-impl</artifactId>
    <version>1.2.5</version>
    <!-- only if angular2json 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
• NotFilterOperator

Java model classes converter

Java classes which describe payload model are generated to TypeScript interfaces. During model serialization to JSON, object mapper is applying some mappings(some of them are required for example in JSON, Date type must be represented as string or number) based on some default configuration or dedicated annotations. Currently Jackson Object mapper is supported. JacksonObjectMapper allows to set fields, getters and setters visibility. Based on this Typescript interface fields are generated. There are supported following Jackson annotations :

• 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

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

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

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

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>1.2.5</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 contains 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)

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