Takes is a true object-oriented and immutable Java8 web development framework. Its key benefits, comparing to all others, include these four fundamental principles:
- Not a single
null
(why NULL is bad?) - Not a single
public
static
method (why they are bad?) - Not a single mutable class (why they are bad?)
- Not a single
instanceof
keyword, type casting, or reflection (why?)
Of course, there are no configuration files. Besides that, these are more traditional features, out of the box:
- Hit-refresh debugging
- XML+XSLT
- JSON
- RESTful
- Templates, incl. Apache Velocity
This is what is not supported and won't be supported:
These two web systems use Takes, and they are open source: wring.io (sources), jare.io (sources).
Watch these videos to learn more: An Immutable Object-Oriented Web Framework and Takes, Java Web Framework, Intro. This blog post may help you too.
- Quick Start
- Build and Run With Maven
- Build and Run With Gradle
- Unit Testing
- Integration Testing
- A Bigger Example
- Templates
- Static Resources
- Hit Refresh Debugging
- Request Methods (POST, PUT, HEAD, etc.)
- Request Parsing
- Form Processing
- Exception Handling
- Redirects
- RsJSON
- RsXembly
- GZIP Compression
- SSL Configuration
- Authentication
- Command Line Arguments
- Logging
- Directory Layout
- Optional dependencies
- Backward compatibility
- Version pattern for RESTful API
- How to contribute
- Got questions?
Create this App.java
file:
import org.takes.http.Exit;
import org.takes.http.FtBasic;
import org.takes.facets.fork.FkRegex;
import org.takes.facets.fork.TkFork;
public final class App {
public static void main(final String... args) throws Exception {
new FtBasic(
new TkFork(new FkRegex("/", "hello, world!")), 8080
).start(Exit.NEVER);
}
}
Then, download takes.jar
and compile your Java code:
$ javac -cp takes.jar App.java
Now, run it like this:
$ java -Dfile.encoding=UTF-8 -cp takes.jar:. App
Should work :)
This code starts a new HTTP server on port 8080 and renders a plain-text page on all requests at the root URI.
Important: Pay attention that UTF-8 encoding is set on the command line.
The entire framework relies on your default Java encoding, which is not
necessarily UTF-8 by default. To be sure, always set it on the command line
with file.encoding
Java argument. We decided not to hard-code "UTF-8" in
our code mostly because this would be against the entire idea of Java localization,
according to which a user always should have a choice of encoding and language
selection. We're using Charset.defaultCharset()
everywhere in the code.
If you're using Maven, this is how your pom.xml
should look like:
<project>
<dependencies>
<dependency>
<groupId>org.takes</groupId>
<artifactId>takes</artifactId>
</dependency>
</dependencies>
<profiles>
<profile>
<id>hit-refresh</id>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.3</version>
<executions>
<execution>
<id>start-server</id>
<phase>pre-integration-test</phase>
<goals>
<goal>java</goal>
</goals>
</execution>
</executions>
<configuration>
<mainClass>foo.App</mainClass> <!-- your main class -->
<cleanupDaemonThreads>false</cleanupDaemonThreads>
<arguments>
<argument>--port=${port}</argument>
</arguments>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
</project>
With this configuration you can run it from command line:
$ mvn clean integration-test -Phit-refresh -Dport=8080
Maven will start the server and you can see it at http://localhost:8080
.
Create a take with constructor accepting ServletContext
:
package com.myapp;
public final class TkApp implements Take {
private final ServletContext ctx;
public TkApp(final ServletContext context) {
this.ctx = context;
}
@Override
public Response act(final Request req) throws Exception {
return new RsText("Hello servlet!");
}
}
Add org.takes.servlet.SrvTake
to your web.xml
, don't forget to specify
take class as servlet init-param
:
<servlet>
<servlet-name>takes</servlet-name>
<servlet-class>org.takes.servlet.SrvTake</servlet-class>
<init-param>
<param-name>take</param-name>
<param-value>com.myapp.TkApp</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>takes</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
If you're using Gradle, this is how your build.gradle
should look like:
plugins {
id 'java'
id 'application'
}
repositories {
mavenCentral()
}
dependencies {
compile group: 'org.takes', name: 'takes', version: '1.11.3'
}
mainClassName='foo.App' //your main class
With this configuration you can run it from command line:
$ gradle run -Phit-refresh -Dport=8080
This is how you can unit test the app, using JUnit 4.x and Hamcrest:
public final class AppTest {
@Test
public void returnsHttpResponse() throws Exception {
MatcherAssert.assertThat(
new RsPrint(
new App().act(new RqFake("GET", "/"))
).printBody(),
Matchers.equalsTo("hello, world!")
);
}
}
You can create a fake request with form parameters like this:
new RqForm.Fake(
new RqFake(),
"foo", "value-1",
"bar", "value-2"
)
Here is how you can test the entire server via HTTP, using JUnit and jcabi-http for making HTTP requests:
public final class AppITCase {
@Test
public void returnsTextPageOnHttpRequest() throws Exception {
new FtRemote(new App()).exec(
new FtRemote.Script() {
@Override
public void exec(final URI home) throws IOException {
new JdkRequest(home)
.fetch()
.as(RestResponse.class)
.assertStatus(HttpURLConnection.HTTP_OK)
.assertBody(Matchers.equalTo("hello, world!"));
}
}
);
}
}
More complex integration testing examples you can find in one of the open source projects that are using Take, for example: rultor.com.
Let's make it a bit more sophisticated:
public final class App {
public static void main(final String... args) {
new FtBasic(
new TkFork(
new FkRegex("/robots\\.txt", ""),
new FkRegex("/", new TkIndex())
),
8080
).start(Exit.NEVER);
}
}
The FtBasic
is accepting new incoming sockets on port 8080,
parses them according to HTTP 1.1 specification and creates instances
of class Request
. Then, it gives requests to the instance of TkFork
(tk
stands for "take") and expects it to return an instance of Take
back.
As you probably understood already, the first regular expression that matches
returns a take. TkIndex
is our custom class,
let's see how it looks:
public final class TkIndex implements Take {
@Override
public Response act(final Request req) {
return new RsHtml("<html>Hello, world!</html>");
}
}
It is immutable and must implement a single method act()
, which is returning
an instance of Response
. So far so good, but this class doesn't have an access
to an HTTP request. Here is how we solve this:
new TkFork(
new FkRegex(
"/file/(?<path>[^/]+)",
new TkRegex() {
@Override
public Response act(final RqRegex request) throws Exception {
final File file = new File(
request.matcher().group("path")
);
return new RsHTML(
FileUtils.readFileToString(file, Charsets.UTF_8)
);
}
}
)
)
We're using TkRegex
instead of Take
, in order to deal with
RqRegex
instead of a more generic Request
. RqRegex
gives an instance
of Matcher
used by FkRegex
for pattern matching.
Here is a more complex and verbose example:
public final class App {
public static void main(final String... args) {
new FtBasic(
new TkFork(
new FkRegex("/robots.txt", ""),
new FkRegex("/", new TkIndex()),
new FkRegex(
"/xsl/.*",
new TkWithType(new TkClasspath(), "text/xsl")
),
new FkRegex("/account", new TkAccount(users)),
new FkRegex("/balance/(?<user>[a-z]+)", new TkBalance())
)
).start(Exit.NEVER);
}
}
Essential part of Bigger Example is
Front interface.
It's encapsulates server's back-end
and used to start an instance, which will accept requests and return results.
FtBasic
, which is a basic front, implements that interface - you've
seen it's usage in above mentioned example.
There are other useful implementations of this interface:
- The FtRemote class allows you to provide script, that will be executed against given front. You can see how it's used in integration tests.
- The FtCli class allows you to start your application with command line arguments. More details in Command Line Arguments.
- The FtSecure class allows you to start your application with SSL. More details in SSL Configuration.
Back interface is the back-end that is responsible for IO operations on TCP network level. There are various useful implementations of that interface:
- The BkBasic class is a basic
implementation of the
Back
interface. It is responsible for accepting the request fromSocket
, converting the socket's input to the Request, dispatching it to the provided Take instance, getting the result and printing it to the socket's output until all the request is fulfilled. - The BkParallel class is
a decorator of the
Back
interface, that is responsible for running the back-end in parallel threads. You can specify the number of threads or try to use the default number, which depends on available processors number in JVM. - The BkSafe class is a decorator
of the
Back
interface, that is responsible for running the back-end in a safe mode. That means that it will ignore exception thrown from originalBack
. - The BkTimeable class is a
decorator of the
Back
interface, that is responsible for running the back-end for specified maximum lifetime in milliseconds. It is constantly checking if the thread with originalback
exceeds provided limit and if so - it's interrupts the thread of thatback
. - The BkWrap class is a convenient
wrap over the original
Back
instance. It's just delegates theaccept
to thatBack
and might be useful if you want to add your own decorators of theBack
interface. This class is used inBkParallel
andBkSafe
as a parent class.
Now let's see how we can render something more complex than a plain text.
First, XML+XSLT is a recommended mechanism of HTML rendering. Even though it may be
too complex, give it a try, you won't regret. Here is how we render a simple XML
page that is transformed to HTML5 on-fly (more about RsXembly
read below):
public final class TkAccount implements Take {
private final Users users;
public TkAccount(final Users users) {
this.users = users;
}
@Override
public Response act(final Request req) {
final User user = this.users.find(new RqCookies(req).get("user"));
return new RsLogin(
new RsXslt(
new RsXembly(
new XeStylesheet("/xsl/account.xsl"),
new XeAppend("page", user)
)
),
user
);
}
}
This is how that User
class may look like:
public final class User implements XeSource {
private final String name;
private final int balance;
@Override
public Iterable<Directive> toXembly() {
return new Directives().add("user")
.add("name").set(this.name).up()
.add("balance").set(Integer.toString(this.balance));
}
}
Here is how RsLogin
may look like:
public final class RsLogin extends RsWrap {
public RsLogin(final Response response, final User user) {
super(
new RsWithCookie(
response, "user", user.toString()
)
);
}
}
Let's say, you want to use Velocity:
public final class TkHelloWorld implements Take {
@Override
public Response act(final Request req) {
return new RsVelocity(
"hi, ${user.name}! You've got ${user.balance}",
new RsVelocity.Pair("user", new User())
);
}
}
You will need this extra dependency in classpath:
<dependency>
<groupId>org.apache.velocity</groupId>
<artifactId>velocity-engine-core</artifactId>
<scope>runtime</scope>
</dependency>
For Gradle users:
dependencies {
...
runtime group: 'org.apache.velocity', name: 'velocity-engine-core', version: 'x.xx'//put the version here
...
}
Very often you need to serve static resources to your web users, like CSS stylesheets, images, JavaScript files, etc. There are a few supplementary classes for that:
new TkFork(
new FkRegex("/css/.+", new TkWithType(new TkClasspath(), "text/css")),
new FkRegex("/data/.+", new TkFiles(new File("/usr/local/data"))
)
Class TkClasspath
take static part of the request URI and finds a resource with this name in classpath.
TkFiles
just looks by file name in the directory configured.
TkWithType
sets content type of all responses coming out of the decorated take.
It is a very convenient feature. Once you start the app you want to be able to modify its static resources (CSS, JS, XSL, etc), refresh the page in a browser and immediately see the result. You don't want to re-compile the entire project and restart it. Here is what you need to do to your sources in order to enable that feature:
new TkFork(
new FkRegex(
"/css/.+",
new TkWithType(
new TkFork(
new FkHitRefresh(
"./src/main/resources/foo/scss/**", // what sources to watch
"mvn sass:compile", // what to run when sources are modified
new TkFiles("./target/css")
)
new FkFixed(new TkClasspath())
),
"text/css"
)
)
)
This FkHitRefresh
fork is a decorator of take. Once it sees
X-Take-Refresh
header in the request, it realizes that the server is running in
"hit-refresh" mode and passes the request to the encapsulated take. Before it
passes the request it tries to understand whether any of the resources
are older than compiled files. If they are older, it tries
to run compilation tool to build them again.
Here is an example:
new TkFork(
new FkRegex(
"/user",
new TkFork(
new FkMethods("GET", new TkGetUser()),
new FkMethods("POST,PUT", new TkPostUser()),
new FkMethods("DELETE", new TkDeleteUser())
)
)
)
Here is how you can parse an instance of Request
:
Href href = new RqHref.Base(request).href();
URI uri = href.uri();
Iterable<String> values = href.param("key");
For a more complex parsing try to use Apache Http Client or something similar.
Here is an example:
public final class TkSavePhoto implements Take {
@Override
public Response act(final Request req) {
final String name = new RqForm(req).param("name");
return new RsWithStatus(HttpURLConnection.HTTP_NO_CONTENT);
}
}
By default, TkFork
lets all exceptions bubble up. If one of your take
crashes, a user will see a default error page. Here is how you can configure
this behavior:
public final class App {
public static void main(final String... args) {
new FtBasic(
new TkFallback(
new TkFork(
new FkRegex("/robots\\.txt", ""),
new FkRegex("/", new TkIndex())
),
new FbChain(
new FbStatus(404, new RsText("sorry, page is absent")),
new FbStatus(405, new RsText("this method is not allowed here")),
new Fallback() {
@Override
public Iterator<Response> route(final RqFallback req) {
return Collections.<Response>singleton(
new RsHTML("oops, something went terribly wrong!")
).iterator();
}
}
)
),
8080
).start(Exit.NEVER);
}
}
TkFallback
decorates an instance of Take and catches all exceptions any of
its take may throw. Once it's thrown, an instance of FbChain
will
find the most suitable fallback and will fetch a response from there.
Sometimes it's very useful to return a redirect response (30x
status code),
either by a normal return
or by throwing an exception. This example
illustrates both methods:
public final class TkPostMessage implements Take {
@Override
public Response act(final Request req) {
final String body = new RqPrint(req).printBody();
if (body.isEmpty()) {
throw new RsForward(
new RsFlash("message can't be empty")
);
}
// save the message to the database
return new RsForward(
new RsFlash(
"thanks, the message was posted"
),
"/"
);
}
}
Then, you should decorate the entire TkFork
with this TkForward
and TkFlash
:
public final class App {
public static void main(final String... args) {
new FtBasic(
new TkFlash(
new TkForward(
new TkFork(new FkRegex("/", new TkPostMessage())
)
),
8080
).start(Exit.NEVER);
}
}
Here is how we can deal with JSON:
public final class TkBalance extends TkFixed {
@Override
public Response act(final RqRegex request) {
return new RsJSON(
new User(request.matcher().group("user")))
);
}
}
This is the method to add to User
:
public final class User implements XeSource, RsJSON.Source {
@Override
public JsonObject toJSON() {
return Json.createObjectBuilder()
.add("balance", this.balance)
.build();
}
}
Here is how you generate an XML page using Xembly:
Response response = new RsXembly(
new XeAppend("page"),
new XeDirectives("XPATH '/page'", this.user)
)
This is a complete example, with all possible options:
Response response = new RsXembly(
new XeStylesheet("/xsl/account.xsl"), // add processing instruction
new XeAppend(
"page", // create a DOM document with "page" root element
new XeMillis(false), // add "millis" attribute to the root, with current time
user, // add user to the root element
new XeSource() {
@Override
public Iterable<Directive> toXembly() {
return new Directives().add("status").set("alive");
}
},
new XeMillis(true), // replace "millis" attribute with take building time
),
)
This is the output that will be produced:
<?xml version='1.0'?>
<?xsl-stylesheet href='/xsl/account.xsl'?>
<page>
<millis>5648</millis>
<user>
<name>Jeff Lebowski</name>
<balance>123</balance>
</user>
<status>alive</status>
</page>
To avoid duplication of all this scaffolding in every page, you can create your own class, which will be used in every page, for example:
Response response = new RsXembly(
new XeFoo(user)
)
This is how this XeFoo
class would look like:
public final class XeFoo extends XeWrap {
public XeFoo(final String stylesheet, final XeSource... sources) {
super(
new XeAppend(
"page",
new XeMillis(false),
new XeStylesheet(stylesheet),
new XeChain(sources),
new XeSource() {
@Override
public Iterable<Directive> toXembly() {
return new Directives().add("status").set("alive");
}
},
new XeMillis(true)
)
);
}
}
You will need this extra dependency in classpath:
<dependency>
<groupId>com.jcabi.incubator</groupId>
<artifactId>xembly</artifactId>
</dependency>
More about this mechanism in this blog post: XML Data and XSL Views in Takes Framework.
Here is how we drop a cookie to the user:
public final class TkIndex implements Take {
@Override
public Response act(final Request req) {
return new RsWithCookie("auth", "John Doe");
}
}
An HTTP response will contain this header, which will place
a auth
cookie into the user's browser:
HTTP/1.1 200 OK
Set-Cookie: auth="John Doe"
This is how you read cookies from a request:
public final class TkIndex implements Take {
@Override
public Response act(final Request req) {
// the list may be empty
final Iterable<String> cookies = new RqCookies(req).cookie("my-cookie");
}
}
If you want to compress all your responses with GZIP, wrap your take in
TkGzip
:
new TkGzip(take)
Now, each request that contains Accept-Encoding
request header with gzip
compression method inside will receive a GZIP-compressed response. Also,
you can compress an individual response, using RsGzip
decorator.
Say, you want to return different content based on Accept
header
of the request (a.k.a. content negotiation):
public final class TkIndex implements Take {
@Override
public Response act(final Request req) {
return new RsFork(
req,
new FkTypes("text/*", new RsText("it's a text"))
new FkTypes("application/json", new RsJSON("{\"a\":1}"))
new FkTypes("image/png", /* something else */)
);
}
}
First of all, setup your keystore settings, for example
final String file = this.getClass().getResource("/org/takes/http/keystore").getFile();
final String password = "abc123";
System.setProperty("javax.net.ssl.keyStore", file);
System.setProperty("javax.net.ssl.keyStorePassword", password);
System.setProperty("javax.net.ssl.trustStore", file);
System.setProperty("javax.net.ssl.trustStorePassword", password);
Then simple create exemplar of class FtSecure with socket factory
final ServerSocket skt = SSLServerSocketFactory.getDefault().createServerSocket(0);
new FtRemote(
new FtSecure(new BkBasic(new TkFixed("hello, world")), skt),
skt,
true
);
Here is an example of login via Facebook:
new TkAuth(
new TkFork(
new FkRegex("/", new TkHTML("hello, check <a href='/acc'>account</a>")),
new FkRegex("/acc", new TkSecure(new TkAccount()))
),
new PsChain(
new PsCookie(
new CcSafe(new CcHex(new CcXOR(new CcCompact(), "secret-code")))
),
new PsByFlag(
new PsByFlag.Pair(
PsFacebook.class.getSimpleName(),
new PsFacebook("facebook-app-id", "facebook-secret")
),
new PsByFlag.Pair(
PsLogout.class.getSimpleName(),
new PsLogout()
)
)
)
)
Then, you need to show a login link to the user, which he or she can click and get to the Facebook OAuth authentication page. Here is how you do this with XeResponse:
new RsXembly(
new XeStylesheet("/xsl/index.xsl"),
new XeAppend(
"page",
new XeFacebookLink(req, "facebook-app-id"),
// ... other xembly sources
)
)
The link will be add to the XML page like this:
<page>
<links>
<link rel="take:facebook" href="https://www.facebook.com/dialog/oauth..."/>
</links>
</page>
Similar mechanism can be used for PsGithub
, PsGoogle
, PsLinkedin
, PsTwitter
, etc.
This is how you get currently logged in user:
public final class TkAccount implements Take {
@Override
public Response act(final Request req) {
final Identity identity = new RqAuth(req).identity();
if (this.identity.equals(Identity.ANONYMOUS)) {
// returns "urn:facebook:1234567" for a user logged in via Facebook
this.identity().urn();
}
}
}
More about it in this blog post: How Cookie-Based Authentication Works in the Takes Framework
There is a convenient class FtCLI
that parses command line arguments and
starts the necessary Front
accordingly.
There are a few command line arguments that should be passed to
FtCLI
constructor:
--port=1234 Tells the server to listen to TCP port 1234
--lifetime=5000 The server will die in five seconds (useful for integration testing)
--hit-refresh Run the server in hit-refresh mode
--daemon Runs the server in Java daemon thread (for integration testing)
--threads=30 Processes incoming HTTP requests in 30 parallel threads
--max-latency=5000 Maximum latency in milliseconds per each request
(longer requests will be interrupted)
For example:
public final class App {
public static void main(final String... args) {
new FtCLI(
new TkFork(new FkRegex("/", "hello, world!")),
args
).start(Exit.NEVER);
}
}
Then, run it like this:
$ java -cp take.jar App.class --port=8080 --hit-refresh
You should see "hello, world!" at http://localhost:8080
.
Parameter --port
also accepts file name, instead of a number. If the file
exists, FtCLI
will try to read its content and use it as
port number. If the file is absent, FtCLI
will allocate a new random
port number, use it to start a server, and save it to the file.
The framework sends all logs to SLF4J logging facility. If you want to see them, configure one of SLF4J bindings.
To make a Take
log, wrap it in a TkSlf4j
- for example:
new TkSlf4j(
new TkFork(...)
)
You are free to use any build tool, but we recommend Maven. This is how your project directory layout may/should look like:
/src
/main
/java
/foo
App.java
/scss
/coffeescript
/resources
/vtl
/xsl
/js
/css
robot.txt
log4j.properties
/test
/java
/foo
AppTest.java
/resources
log4j.properties
pom.xml
LICENSE.txt
If you're using Maven and include Takes as a dependency in your own project,
you can choose which of the optional dependencies to include in your project.
The list of all of the optional dependencies can be seen in the Takes project pom.xml
.
For example, to use the Facebook API shown above, simply add a dependency to
the restfb
API in your project:
<dependency>
<groupId>com.restfb</groupId>
<artifactId>restfb</artifactId>
<version>1.15.0</version>
<scope>runtime</scope>
</dependency>
For Gradle, you should add the dependencies as usual:
dependencies {
...
runtime group: 'com.restfb', name: 'restfb', version: '1.15.0'
}
Version 2.0 is not backward compatible with previous versions.
The URL should NOT contain the versions, but the type requested.
For example:
===>
GET /architect/256 HTTP/1.1
Accept: application/org.takes.architect-v1+xml
<===
HTTP/1.1 200 OK
Content-Type: application/org.takes.architect-v1+xml
<architect>
<name>Yegor Bugayenko</name>
</architect>
Then clients aware of newer version of this service can call:
===>
GET /architect/256 HTTP/1.1
Accept: application/org.takes.architect-v2+xml
<===
HTTP/1.1 200 OK
Content-Type: application/org.takes.architect-v2+xml
<architect>
<firstName>Yegor</firstName>
<lastName>Bugayenko</lastName>
<salutation>Mr.</salutation>
</architect>
This article explains why itΒ΄s done this way.
Fork repository, make changes, send us a pull request. We will review
your changes and apply them to the master
branch shortly, provided
they don't violate our quality standards. To avoid frustration, before
sending us your pull request please run full Maven build:
$ mvn clean install -Pqulice
To avoid build errors use maven 3.2+.
Pay attention that our pom.xml
inherits a lot of configuration
from jcabi-parent.
This article
explains why it's done this way.