Light Codegen

Why this generator

In the earlier days of light-platform, we only had a Restful framework, and we were leveraging swagger-codegen to generate our projects from Swagger 2.0 specifications. However, there are several issues that we could not resolve.

swagger-codegen does not support Java 8 and Java 11, so we have to fork it and customize it.
swagger-codegen does not give your flexibility to customize the project. For example, if Oracle Database is supported.
swagger-codegen can only support the swagger specification, and we later added GraphQL and Hybrid frameworks
swagger-codegen is very slow, and it takes several seconds to generate a project. Light-codegen needs several milli-seconds so that we can support code generation from the web.
swagger-codegen does not support external extension, which means you have to add your generator to the codebase to work.

Given all the drawbacks, we have decided to build our generator. light-codegen is built with Java 8/11 and uses the rocker template engine that compiles the templates to Java class to speed it up. It also uses our IoC service module to enable new generators to be added without touch the source code.

OpenAPI Lambda Generator

This generator is based on the OpenAPI 3.0 specification to generate one AWS Lamdbd function per endpoint. Also, it generates all the artifacts for the building and deploying with cloud formation YAML files. Input Model In light-rest-4j framework generator, the model that drives code generation is the OpenAPI 3.0 specification previously named Swagger specification. When editing it, it usually will be in YAML format with separate files for readability and flexibility. Read More »

Download vs Build light-codegen

Most users are using the Java command line to invoke light-codegen to generate projects locally. You can download the codegen-cli.jar from the release page or clone the light-codegen repository and build locally. The easiest way is to download the codegen-cli.jar from the release page. For each release, we upload the fat jar to the release page as an asset for users to download. Once the file is downloaded, put into a working directory like ~/tool or ~/networknt and run the command line from the same folder. Read More »

Dockerfile

Light-codegen generates a docker folder in the root of the target project, and this folder contains several Dockerfiles to build different Docker images. For 1.6.x Java 8 branch, we have a default Dockerfile based on the Alpine image and Dockerfile-RedHat based on the RedHat image for some enterprise customers. When we move to Java 11, we have added several more Dockerfiles. Dockerfile FROM openjdk:11.0.3-slim ADD /target/light-router.jar server.jar CMD ["/bin/sh","-c","java -Dlight-4j-config-dir=/config -Dlogback. Read More »

OpenAPI Kotlin Generator

This generator is based on the OpenAPI 3.0 specification, and it is a new specification that is supposed to replace the Swagger 2.0 specification. It has some significant changes to enhance the spec definition and simply validate with only JSON schema. In my opinion, it is much easier to use, and the implementation is much simpler then Swagger 2.0. OpenAPI adds a number of features as well. The only issue I can see is the entire toolchains around Swagger 2. Read More »

Hybrid Server

Hybrid server is a special project that is designed as a host server for services built on top of light-hybrid-4j framework. Every service is built as a small jar file with only the business logic handlers inside. Multiple jar files can be put into a docker volume to be loaded by a hybrid server instance running in docker container. In this way, the developer has nothing to do with the server at all they just need to focus on their domain business logic. Read More »

Hybrid Service

This is a generator that scaffolds hybrid services which is on top of light-hybrid-4j and light-4j frameworks. Hybrid framework contains a set of handlers to support RPC style of contract instead of Restful to eliminate the complex transformation between model and URI and vice verse. Currently we only support JSON RPC and binary RPC will be supported if there are requests. Another benefit of the hybrid framework is that services can be composed as a modular monolith and running within the same JVM in the beginning and then split them into several JVM later on if load is getting higher. Read More »

Eventuate Generator

Light-codegen provides a generator to generate the eventuate base API based on OpenAPI 3.0 specification. The eventuate based API is built based on light-eventuate-4j framework. light-eventuate-4j framework design eventuate microservice API based on CQRS (Command Query Responsibility Segregation) design pattern. The service specification defined for Eventuate based API code generator should include the service definition for both CQRS command side service and query side service. The command side service will publish the event to event store to change the state of the domain object or entire system. Read More »

Hybrid Generator

Graphql Generator

These days, GraphQL is getting popular and many companies have adopted it to build their API and github.com is one of them. In most cases, developer will write their schema code with their favorite language and then wire in the business logic into the resolvers. Recently there is a IDL defined by the community; although it is not a standard yet, there are a lot of big players that supprot it. Read More »

OpenAPI Generator

This generator is based on the OpenAPI 3.0 specification, and it is a very new specification that is supposed to replace Swagger 2.0 specification. It has some significant changes to enhance the spec definition and simply the validate with only JSON schema. In my opinion, it is much easier to use, and the implementation is much simpler than Swagger 2.0. Input Model In light-rest-4j framework generator, the model that drives code generation is the OpenAPI 3. Read More »

Swagger Generator

This generator is based on Swagger 2.0 specification and it is the most popular specification format for Restful API these days. Although it might be replaced soon with OpenAPI 3.0, this is still the main style in light-rest-4j framework. A lot of our customers are using it to build their restful APIs. In light-rest-4j, we use the specification to scaffold the project and we also use the specification during runtime for OAuth 2. Read More »

Multi Framework

Whether or not you are using the command line or the website to generate code, you can choose more than one framework at a time to combine the framework code together. Normally, you choose one to generate the backend service and another one to generate the front-end single page application based on Angular or React. For the command line tool, you can choose to generate the backend service first to a target directory and then run another command line to generate the front end application into the same target folder. Read More »

Customization

light-codegen is a generic code generator based Rocker template engine. It can be extended to support other frameworks or other languages. You just need to package the new generator along with template files into a jar and put the jar file into the classpath of light-codegen to make it work. In order for the light-codegen to find your new generator, you need to externalize service.yml to add your generator implementation into it. Read More »

Integration

Most users use the generator in Java command line, docker command line or script which can be easily integrated with any DevOps pipeline. For users who want to integrate the generator with the maven build, please refer to Integrate Code generation with maven build process For users who do not want to clone and build the generator locally, we provide a web service with UI so that you can generate project remotely and then download/build locally. Read More »

Best Practice

Before using light-codegen to scaffold a new project, a specification file must be designed and passed to light-codegen along with a config.json file. To make the generated code more meaningful, you need to put some design effort into the spec. Here are some of the best practices for RESTful Swagger 2.0 and OpenAPI 3.0 specifications. Swagger 2.0 Best Practices OpenAPI 3.0 Best Practices Read More »

With support for rocker hot reloading, light-codegen can load customized templates and render classes so that each organization can generate content specific to their own frameworks built on the top of light-4j frameworks. Usage To enable rocker hot reloading, extra classpath setting is needed. A script codegen-cli/codegen.sh is provided to help the code generation with hot reloading. MacOS Setting the directory of customized templates in codegen.sh, for example src/test/resources/externalTemplates/ Read More »