play framework2學習之旅Actions, Controllers and Results

Actions, Controllers and Results

What is an Action?

Most of the requests received by a Play application are handled by an Action.

An action is basically a Java method that processes the request parameters, and produces a result to be sent to the client.

public static Result index() {
  return ok("Got request " + request() + "!");
}

An action returns a play.mvc.Result value, representing the HTTP response to send to the web client. In this example ok constructs a 200 OK response containing atext/plain response body.

我的認識：客戶端-->發起請求（此請求帶有一定的參數）--->由action方法接受並處理請求參數--->將處理結果以play.mvc.Result形式返回

Controllers

A controller is nothing more than a class extending play.mvc.Controller that groups several action methods.

The simplest syntax for defining an action is astaticmethod with no parameters thatreturns a Result value:

public static Result index() {
  return ok("It works!");
}

An action method can also have parameters:

public static Result index(String name) {
  return ok("Hello" + name);
}

These parameters will be resolved by the Router and will be filled with values from the request URL. The parameter values can be extracted from either the URL path or the URL query string.

我的認識：controllers就是一個繼承自play.mvc.Controller的類，起一箇中介作用，它就是action的容身之處，不過要注意所有的方法都是靜態的！

Results

Let’s start with simple results: an HTTP result with a status code, a set of HTTP headers and a body to be sent to the web client.

These results are defined by play.mvc.Result, and the play.mvc.Results class provides several helpers to produce standard HTTP results, such as the ok method we used in the previous section:

public static Result index() {
  return ok("Hello world!");
}

Here are several examples that create various results:

Result ok = ok("Hello world!");
Result notFound = notFound();
Result pageNotFound = notFound("<h1>Page not found</h1>").as("text/html");
Result badRequest = badRequest(views.html.form.render(formWithErrors));
Result oops = internalServerError("Oops");
Result anyStatus = status(488, "Strange response type");

All of these helpers can be found in the play.mvc.Results class.

我的認識：只要記住最後一句話即可，所有的這些都可以在play.mvc.Results class中查到，到時候查API即可！

Redirects are simple results too

Redirecting the browser to a new URL is just another kind of simple result. However, these result types don’t have a response body.

There are several helpers available to create redirect results:

public static Result index() {
  return redirect("/user/home");
}

The default is to use a 303 SEE_OTHER response type, but you can also specify a more specific status code:

public static Result index() {
  return temporaryRedirect("/user/home");
}

關於重定向，只要記住這兩個方法即可，但要記得default是temporaryRedirect;

public static Result temporaryRedirect(java.lang.String url)