[JAVA] Getting Started with Ratpack (4)-Routing & Static Content

Ratpack introductory series

1. Introduction to Ratpack (1) --What is Ratpack
2. Introduction to Ratpack (2) --Architecture
3. Introduction to Ratpack (3) --Hello world detailed explanation
4. Introduction to Ratpack (4) --Routing & Static Content
5. Introduction to Ratpack (5) --Json & Registry
6. Introduction to Ratpack (6) --Promise
7. Introduction to Ratpack (7) --Guice & Spring
8. Introduction to Ratpack (8) --Session
9. Introduction to Ratpack (9) --Thymeleaf

routing

As mentioned above, routing is done by writing a handler that maps to each path in the Chain class. The official documentation is in Chain's Javadoc, so please refer to that if you can't explain it here. ..

Each method for adding a Handler

The most basic method in Chain is ʻall (Handler), which indicates that all requests will be processed by this handler. Each of the other methods is actually just a convenience method with a "request acceptance condition" added to this method. Internally, each static utility method of Handlers processes by wrapping the passed Handler`.

Those that take Class <Handler> as arguments instead of the instance of Handler itself will use that class from the context's Registry. It doesn't seem to make much sense, but it works great when combined with a DI container such as Guice.

Below, I will explain the main methods (all are impossible due to the large amount).

chain.prefix( "hoge", innerChain -> {
    innerChain.get( "piyo", handler );  // /hoge/piyo
} );

In addition, Context provides convenience methods calledbyMethod ()and byContent, which allow you to describe branches ideologically.

//path"hoge"Branch with GET and POST when is requested
chain.path( "hoge", ctx -> {
    ctx.byMethod( m -> {
        m.get( iCtx -> iCtx.render( "get" ) );
        m.post( iCtx -> iCtx.render( "post" ) );
    } );
} );

// "hoge"Of the request`Accept`Branch by the value of the header
chain.path( "hoge", ctx -> ctx.byContent( accept -> {
    accept.json( iCtx -> iCtx.render("json") );
    accept.xml( iCtx -> iCtx.render( "xml" ) );
    accept.noMatch( iCtx -> iCtx.render( "no match" ) );
} ) );

By the way, the variable name is written in solid here, but it can also be described in the method chain.

Path literal

Literals such as regular expressions can be used for the character string specified in the path, and path parameters can also be set.

(Translated from Javadoc)

Path parameters can be obtained via the PathTokens class, which can be obtained withContext.getPathToken ().

chain.get( "hoge/:name", ctx -> ctx.render( "name: " + ctx.getPathTokens().get( "name" ) ) );
chain.get( "piyo/:id:\\d+", ctx -> ctx.render( "id: " + ctx.getPathTokens().asLong( "id" ) ) );

Behavior of Context

The Context class is a class that holds information on how a single request is called. As we saw in Hello world, Handler is a lambda expression that receives Context. Therefore, the flow of processing is Receive Context-> Perform various processing-> Call Context.render () to create a response It will be in the form of.

Query parameters

This is the part after ? Of the URL. You can get it as a map from getRequest (). GetQueryParams ().

Path parameter

As mentioned above, use getPathToken ().

FORM parameter

Form parameters sent from HTTP <form> tags etc. are obtained via the Form class using theparse ()method.

chain.path( "hoge", ctx -> ctx.parse( Form.class ).then( form -> {
    ctx.render( "Received: " + form.entrySet() );
} ) );

parse () will be described later.

Request body

You can get it from getRequest (). getBody (). It's important to note that the getBody () method returns the body's Promise, not the body's contents. How to use Promise will be explained in a future post.

header

Get it via the Headers class, which you can get fromheader (CharSequence)orgetRequest (). GetHeaders ().

cookie

You can get it with Request.getCookies ().

Returns a response

To set the response, get the Response class fromgetResponse ()and set it in that instance. The actual transmission is done with Context.render (Object) or Response.send ().

Status code

It can be specified by the status (int) method.

cookie

The Cookie class is created by calling thecookie ()method. There is no need to add the returned Cookie object to the set returned by thegetCookies ()method.

header

You can get a variable set of headers with Response.getHeaders (). Convenience methods such as contentType () are also available.

Context.redirect(String) 302 Generates a redirect and transitions to the specified path.

Context.clientError(int) It is used when you want to generate an error in the status code 400 series. For 404s, the convenience method notFound () is provided.

Context.render(Object) This is the most basic method that returns a response.

BaseDir

To serve static files, Ratpack provides a mechanism called BaseDir.

First, you need to set the BaseDir Path to ServerConfig. You can create the JDK Path normally, but there is aBaseDir.find ()method for loading resources from the class loader. There is also a convenience method called ServerConfigBuilder.findBaseDir (). find () looks for an empty file called .ratpack in the specified path. If found, it will serve static content using that path as an internal reference path. Next, we need to create a handler that serves the file from BaseDir. The Chain.files () method sends the contents of the file as a response when there is a request from the BaseDir set above to the URL resolved as a relative path.

This is a concrete example. Here, create a folder called public in the resource and set it to BaseDir.

Create the following as a resource. resources/public/.ratpack resources/public/index.html

Path baseDir = BaseDir.find( "public/.ratpack" );

ServerConfig config = ServerConfig.builder()
                                  .baseDir( baseDir )
                                  .development( true ).build();

Action<Chain> handlers = chain -> {
    chain.files();
};

RatpackServer.start( server -> server
        .serverConfig( config )
        .handlers( handlers ) );

Go to http: //localhost:5050/index.html and you should see the contents of the HTML file you created.

If you want to bind the file to your own path, pass Path to theContext.render ()method. You can use the Context.file () method to get the file from BaseDir.

Try changing the handler in the above example as follows:

Action<Chain> handlers = chain -> {
    chain.files();
    chain.get( "hoge", ctx -> ctx.render( ctx.file( "index.html" ) ) );
};

If you visit http: // localhost: 5050 / hoge, you will see the contents of ʻindex.html`.