public interface Context extends MinimalContext
Handler invocation.
It provides:
request and responsenext() and insert(ratpack.handling.Handler...) family of methods)
A context is also a Registry of objects.
Arbitrary objects can be "pushed" into the context for use by downstream handlers.
There are some significant contextual objects that drive key infrastructure.
For example, error handling is based on informing the contextual ServerErrorHandler of exceptions.
The error handling strategy for an application can be changed by pushing a new implementation of this interface into the context that is used downstream.
See insert(Handler...) for more on how to do this.
There is also a set of default objects that are made available via the Ratpack infrastructure:
LaunchConfigFileSystemBinding that is the application LaunchConfig.getBaseDir()MimeTypes implementationServerErrorHandlerClientErrorHandlerFileRendererBindAddressPublicAddressRedirector| Modifier and Type | Method and Description |
|---|---|
void |
clientError(int statusCode)
Forwards the error to the
ClientErrorHandler in this service. |
ByContentHandler |
getByContent()
A buildable handler useful for performing content negotiation.
|
ByMethodHandler |
getByMethod()
A buildable handler for conditional processing based on the HTTP request method.
|
Context |
getContext()
Returns this.
|
DirectChannelAccess |
getDirectChannelAccess()
Provides direct access to the backing Netty channel.
|
Response |
getResponse()
The HTTP response.
|
void |
insert(Handler... handlers)
Inserts some handlers into the pipeline, then delegates to the first.
|
void |
insert(Registry registry,
Handler... handlers)
Inserts some handlers into the pipeline to execute with the given registry, then delegates to the first.
|
void |
lastModified(Date date,
Runnable runnable)
Convenience method for handling last-modified based HTTP caching.
|
void |
next()
Delegate handling to the next handler in line.
|
void |
next(Registry registry)
Invokes the next handler, after adding the given registry.
|
<T> T |
parse(Class<T> type)
Shorthand for no option parses.
|
<T> T |
parse(Parse<T> parse)
Parses the request body into an object.
|
void |
redirect(int code,
String location)
Sends a redirect response location URL and status code (which should be in the 3xx range).
|
void |
redirect(String location)
Sends a temporary redirect response (i.e.
|
void |
render(Object object)
Render the given object, using the rendering framework.
|
void |
respond(Handler handler)
Convenience method for delegating to a single handler.
|
<T> ResultAction<T> |
resultAction(Action<T> action)
Creates a result action that uses the contextual error handler if the result is failure.
|
void |
withErrorHandling(Runnable runnable)
Executes the given runnable in a try/catch, where exceptions are given to
MinimalContext.error(Exception). |
background, error, file, getAllPathTokens, getBackground, getBindAddress, getForeground, getPathTokens, getRequest, onCloseContext getContext()
getContext in interface MinimalContextResponse getResponse()
@NonBlocking void next()
The request and response of this object should not be accessed after this method is called.
@NonBlocking void next(Registry registry)
The given registry is appended to the existing. This means that it can shadow objects previously available.
import ratpack.handling.Handler;
import ratpack.handling.Handlers;
import ratpack.handling.Chain;
import ratpack.handling.ChainAction;
import ratpack.handling.Context;
import ratpack.launch.HandlerFactory;
import ratpack.launch.LaunchConfig;
import ratpack.launch.LaunchConfigBuilder;
import ratpack.func.Factory;
import static ratpack.registry.Registries.registry;
public interface SomeThing {}
public class SomeThingImpl implements SomeThing {}
public class UpstreamHandler implements Handler {
public void handle(Context context) {
context.next(registry(SomeThing.class, new SomeThingImpl()));
}
}
public class DownstreamHandler implements Handler {
public void handle(Context context) {
SomeThing someThing = context.get(SomeThing.class); // instance provided upstream
assert someThing instanceof SomeThingImpl;
// …
}
}
LaunchConfigBuilder.baseDir(new File("base")).build(new HandlerFactory() {
public Handler create(LaunchConfig launchConfig) {
return Handlers.chain(launchConfig, new ChainAction() {
public void execute(Chain chain) {
chain.handler(new UpstreamHandler());
chain.handler(new DownstreamHandler());
}
});
}
});
registry - The registry to make available for subsequent handlers.@NonBlocking void insert(Handler... handlers)
The request and response of this object should not be accessed after this method is called.
handlers - The handlers to insert.@NonBlocking void insert(Registry registry, Handler... handlers)
The given registry is only applicable to the inserted handlers.
Almost always, the registry should be a super set of the current registry.
handlers - The handlers to insertregistry - The registry for the inserted handlers@NonBlocking void respond(Handler handler)
Designed to be used in conjunction with the getByMethod() and getByContent() methods.
handler - The handler to invokeByContentHandler,
ByMethodHandlerByMethodHandler getByMethod()
ByContentHandler getByContent()
@NonBlocking void clientError(int statusCode) throws NotInRegistryException
ClientErrorHandler in this service.
The default configuration of Ratpack includes a ClientErrorHandler in all contexts.
A NotInRegistryException will only be thrown if a very custom service setup is being used.statusCode - The 4xx range status code that indicates the error typeNotInRegistryException - if no ClientErrorHandler can be found in the servicevoid withErrorHandling(Runnable runnable)
MinimalContext.error(Exception).
This can be used by handlers when they are jumping off thread. Exceptions raised on the thread that called the handler's handle will always be caught. If the handler “moves” to another thread, it should call this method no the new thread to ensure that any thrown exceptions are caught and forwarded appropriately.
runnable - The code to surround with error handling<T> ResultAction<T> resultAction(Action<T> action)
The given action is invoked if the result is successful.
T - The type of the successful result valueaction - The action to invoke on a successful result.Result<T>@NonBlocking void render(Object object)
The first Renderer, that is able to render the given object will be delegated to.
If the given argument is null, this method will have the same effect as clientError(404).
If no renderer can be found for the given type, a NoSuchRendererException will be given to MinimalContext.error(Exception).
If a renderer throws an exception during its execution it will be wrapped in a RendererException and given to MinimalContext.error(Exception).
Ratpack has built in support for rendering the following types:
Path (see FileRenderer)CharSequence (see CharSequenceRenderer)
See Renderer for more on how to contribute to the rendering framework.
object - The object to rendervoid redirect(String location) throws NotInRegistryException
location - the redirect location URLNotInRegistryException - if there is no Redirector in the current service but one is provided by defaultvoid redirect(int code,
String location)
throws NotInRegistryException
code - The status code of the redirectlocation - the redirect location URLNotInRegistryException - if there is no Redirector in the current service but one is provided by default@NonBlocking void lastModified(Date date, Runnable runnable)
The given date is the "last modified" value of the response. If the client sent an "If-Modified-Since" header that is of equal or greater value than date, a 304 will be returned to the client. Otherwise, the given runnable will be executed (it should send a response) and the "Last-Modified" header will be set by this method.
date - The effective last modified date of the responserunnable - The response sending action if the response needs to be sent<T> T parse(Parse<T> parse) throws NoSuchParserException, ParserException
How to parse the request is controlled by the given Parse object.
Parser resolution happens as follows:
parsers are retrieved from the context registry (i.e. getAll(Parser.class));getAll()) for compatibility with the given parse object and the current request content type;Parser.parse(Context, ratpack.http.TypedData, ratpack.parse.Parse) method is called, of which the return value is returned by this method;NoSuchParserException will be thrown.A parser is compatible if all of the following hold true:
Parser.getContentType() is exactly equal to getRequest().getBody().getContentType().getType()parse object is an instanceof its Parser.getParseType()Parser.getParsedType() is Class.isAssignableFrom(Class) the Parse.getType() of the parse object
If the request has no declared content type, text/plain will be assumed.
Ratpack core provides implicit parsers for the following parse and content types:
Form
import ratpack.handling.Handler;
import ratpack.handling.Context;
import ratpack.form.Form;
import static ratpack.parse.NoOptParse.to;
public class FormHandler implements Handler {
public void handle(Context context) {
Form form = context.parse(to(Form.class));
context.render(form.get("someFormParam"));
}
}
T - The type of object the request is parsed intoparse - The specification of how to parse the requestNoSuchParserException - if no suitable parser could be found in the registryParserException - if a suitable parser was found, but it threw an exception while parsingParser<T> T parse(Class<T> type) throws NoSuchParserException, ParserException
The code sample is functionally identical to the sample given for the parse(ratpack.parse.Parse) variant…
import ratpack.handling.Handler;
import ratpack.handling.Context;
import ratpack.form.Form;
public class FormHandler implements Handler {
public void handle(Context context) {
Form form = context.parse(Form.class);
context.render(form.get("someFormParam"));
}
}
That is, it is effectively a convenient wrapper around NoOptParse.to(Class).
T - the type to parse totype - the type to parse toNoSuchParserException - if no suitable parser could be found in the registryParserException - if a suitable parser was found, but it threw an exception while parsingDirectChannelAccess getDirectChannelAccess()
General only useful for low level extensions. Avoid if possible.