Trimness

Trimness aims to be an extensible tool to build a lightweight service for rendering templates (e.g. a simple reporting application). It's built on several open source projects. The fundamental ones are Trimou (mustache/handlebars-like templating engine), Weld (component model, extensibility) and Vert.x (web server, routing, event bus).

Available in the Maven Central Repository

<dependency>
  <groupId>org.trimou</groupId>
  <artifactId>trimness-core</artifactId>
  <version>${version.trimness}</version>
</dependency>

Get started

The best place to start is probably the simple example. Clone the repository, build the project and run the example shaded jar:

$ git clone [email protected]:trimou/trimness.git
$ mvn clean install
$ java -jar examples/simple/target/trimness-example-simple-shaded.jar

A simple UI with test form is located at localhost:8080/test. Insert commits-list.html in template id field and hit render button. You should get a link to a result - HTML page with list of last commits from this repository.

How does it work?

Trimness's business is to render templates. There are two ways to send a "render request".

1. HTTP endpoints
2. Vert.x event bus

HTTP endpoints

HTTP method	Path	Consumes	Description
POST	/render	application/json	Send sync/async render request
GET	/result/{resultId}	-	Get the result of a render request
DELETE	/result/{resultId}	-	Remove the result of a render request
GET	/result/link/{linkId}	-	Get the result for the specified link
GET	/monitor/health	-	Simple health-check resource
GET	/template/{id}	-	Attempt to find the template with the given id

Basics

Let's use curl to perform a very simple render request:

curl -X POST -H "Content-Type: application/json" -d '{ "templateContent" : "Hello {{model.name}}!", "model" : { "name" : "Foo"} }' http://localhost:8080/render

The reply should be Hello Foo!. Let's analyze the request payload. content property is used to specify the template for one-off rendering (TIP: it's much better to leverage the template providers and template cache - see below). model property holds the data used during rendering (TIP: model is not the only source of data - see model providers below).

Asynchronous render requests

By default, the request is synchronous which means that the client is waiting for the rendered output. If we change the payload to:

{ "templateContent" : "Hello {{model.name}}!", "model" : { "name" : "Foo"}, "async": true }

Then trimness replies immediately with something like:

{ "time" : "2017-05-19T11:25:50.393", "resultId" : "1495185748798", "timeout" : "2017-05-19T11:30:50.393"}

time is the current server time. timeout is the time after which the result might be removed automatically (it depends on the underlying result repository implementation). The resultId is used to pick up the result later:

curl http://localhost:8080/result/1495185748798

And the reply should be again Hello Foo!.

Result links

Sometimes it might be useful to specify a more memorable link that could be used instead of the result id:

{ "templateContent" : "Hello {{model.name}}!", "model" : { "name" : "Foo"}, "async": true, "linkId" : "foo-1" }

linkId is used to specify a link that could be also used to get the result:

curl http://localhost:8080/result/link/foo-1

Result metadata

We can also specify the result type:

curl http://localhost:8080/result/1495185748798?resultType=metadata

In this case, the reply would be:

{ "time" : "2017-05-19T11:25:50.393", "result" : { "id" : "1495185748798", "templateId" : "oneoff_1495201157642", "output" : "Hello Foo!", "status" : "SUCCESS" }}

Vert.x Event Bus

Vert.x message consumers are automatically registered for addresses listed below. The message/reply payload is always JSON and follows the contract used for HTTP endpoints (where possible).

Address	Description
org.trimou.trimness.render	Sync/async render request
org.trimou.trimness.result	Get the result of a render request
org.trimou.trimness.result.remove	Remove the result of a render request
org.trimou.trimness.result.link	Get the result for the specified link

Extension points

Template provider

The template provider is responsible for looking up and loading contents of the templates. There might be several template providers installed. Providers with higher priority are queried first. There are two built-in template providers available. FileSystemTemplateProvider which loads templates from the local filesystem. And ClassPathTemplateProvider which loads templates from the class path.

Model provider

Provides data models for templates. The model can be used in templates - the result set via ModelRequest#complete(Object) is accessible under the namespace key (defined by getNamespace()). If a model request is not processed within TrimnessKey#MODEL_INIT_TIMEOUT the potential result is ignored afterwards. A simple example is the GithubModelProvider. This model provider fetches info about repository commits using api.github.com which is later used in the template. There is one built-in model provider - GlobalJsonModelProvider which attempts to read a JSON file from the class path or the filesystem and if it exists and can be read, then provide all the data found to all templates.

Result repository

This component is used to store the results of render requests. A valid repository with the highest priority is used. By default, InMemoryResultRepository is used. If org.trimou.trimness.resultDir property is set and represents a valid directory path then FileSystemResultRepository is used instead. This repository is slower but results survive application restart.

Configuration

Trimness can be configured through system properties, environment variables and trimness.properties file. The built-in options are listed in an enum: https://github.com/trimou/trimness/blob/master/core/src/main/java/org/trimou/trimness/config/TrimnessKey.java.

Packaging and deployment

Trimness is not meant to be deployed to a container (such as Java EE). Instead, add trimness-core.jar and its dependencies to the class path of your application or use maven-shade-plugin to build a fat jar, see for example: https://github.com/trimou/trimness/blob/master/examples/simple/pom.xml#L25.