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A Sinatra inspired framework for java
Java
branch: master

README.md

Spark - a Sinatra inspired web framework

For more detailed documentation please go to: http://sparkjava.com

NEWS: Spark 2.2 is now available on Maven central! :

    <dependency>
        <groupId>com.sparkjava</groupId>
        <artifactId>spark-core</artifactId>
        <version>2.2</version>
    </dependency>

NEWS: Spark google group created: https://groups.google.com/d/forum/sparkjava

Temporary API Docs: http://spark.screenisland.com

Getting started

import static spark.Spark.*;

public class HelloWorld {

    public static void main(String[] args) {

        get("/hello", (request, response) -> "Hello World!");
    }
}

View at: http://localhost:4567/hello

More documentation is on the way!

Check out and try the examples in the source code. You can also check out the javadoc. After getting the source from github run:

mvn javadoc:javadoc

The result is put in /target/site/apidocs

Examples

Simple example showing some basic functionality

import static spark.Spark.*;

/**
 * A simple example just showing some basic functionality
 */
public class SimpleExample {

    public static void main(String[] args) {

        //  port(5678); <- Uncomment this if you want spark to listen on a port different than 4567

        get("/hello", (request, response) -> "Hello World!");

        post("/hello", (request, response) ->
            "Hello World: " + request.body()
        );

        get("/private", (request, response) -> {
            response.status(401);
            return "Go Away!!!";
        });

        get("/users/:name", (request, response) -> "Selected user: " + request.params(":name"));

        get("/news/:section", (request, response) -> {
            response.type("text/xml");
            return "<?xml version=\"1.0\" encoding=\"UTF-8\"?><news>" + request.params("section") + "</news>";
        });

        get("/protected", (request, response) -> {
            halt(403, "I don't think so!!!");
            return null;
        });

        get("/redirect", (request, response) -> {
            response.redirect("/news/world");
            return null;
        });

        get("/", (request, response) -> "root");
    }
}

A simple CRUD example showing howto create, get, update and delete book resources

import static spark.Spark.*;

import java.util.HashMap;
import java.util.Map;
import java.util.Random;

/**
 * A simple CRUD example showing howto create, get, update and delete book resources.
 */
public class Books {

    /**
     * Map holding the books
     */
    private static Map<String, Book> books = new HashMap<String, Book>();

    public static void main(String[] args) {
        final Random random = new Random();

        // Creates a new book resource, will return the ID to the created resource
        // author and title are sent as query parameters e.g. /books?author=Foo&title=Bar
        post("/books", (request, response) -> {
            String author = request.queryParams("author");
            String title = request.queryParams("title");
            Book book = new Book(author, title);

            int id = random.nextInt(Integer.MAX_VALUE);
            books.put(String.valueOf(id), book);

            response.status(201); // 201 Created
            return id;
        });

        // Gets the book resource for the provided id
        get("/books/:id", (request, response) -> {
            Book book = books.get(request.params(":id"));
            if (book != null) {
                return "Title: " + book.getTitle() + ", Author: " + book.getAuthor();
            } else {
                response.status(404); // 404 Not found
                return "Book not found";
            }
        });

        // Updates the book resource for the provided id with new information
        // author and title are sent as query parameters e.g. /books/<id>?author=Foo&title=Bar
        put("/books/:id", (request, response) -> {
            String id = request.params(":id");
            Book book = books.get(id);
            if (book != null) {
                String newAuthor = request.queryParams("author");
                String newTitle = request.queryParams("title");
                if (newAuthor != null) {
                    book.setAuthor(newAuthor);
                }
                if (newTitle != null) {
                    book.setTitle(newTitle);
                }
                return "Book with id '" + id + "' updated";
            } else {
                response.status(404); // 404 Not found
                return "Book not found";
            }
        });

        // Deletes the book resource for the provided id
        delete("/books/:id", (request, response) -> {
            String id = request.params(":id");
            Book book = books.remove(id);
            if (book != null) {
                return "Book with id '" + id + "' deleted";
            } else {
                response.status(404); // 404 Not found
                return "Book not found";
            }
        });

        // Gets all available book resources (id's)
        get("/books", (request, response) -> {
            String ids = "";
            for (String id : books.keySet()) {
                ids += id + " ";
            }
            return ids;
        });
    }

    public static class Book {

        public String author, title;

        public Book(String author, String title) {
            this.author = author;
            this.title = title;
        }

        public String getAuthor() {
            return author;
        }

        public void setAuthor(String author) {
            this.author = author;
        }

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }
    }
}

Example showing a very simple (and stupid) authentication filter that is executed before all other resources

import static spark.Spark.*;

import java.util.HashMap;
import java.util.Map;

/**
 * Example showing a very simple (and stupid) autentication filter that is
 * executed before all other resources.
 *
 * When requesting the resource with e.g.
 *     http://localhost:4567/hello?user=some&password=guy
 * the filter will stop the execution and the client will get a 401 UNAUTHORIZED with the content 'You are not welcome here'
 *
 * When requesting the resource with e.g.
 *     http://localhost:4567/hello?user=foo&password=bar
 * the filter will accept the request and the request will continue to the /hello route.
 *
 * Note: There is a second "before filter" that adds a header to the response
 * Note: There is also an "after filter" that adds a header to the response
 */
public class FilterExample {

    private static Map<String, String> usernamePasswords = new HashMap<String, String>();

    public static void main(String[] args) {

        usernamePasswords.put("foo", "bar");
        usernamePasswords.put("admin", "admin");

        before((request, response) -> {
            String user = request.queryParams("user");
            String password = request.queryParams("password");

            String dbPassword = usernamePasswords.get(user);
            if (!(password != null && password.equals(dbPassword))) {
                halt(401, "You are not welcome here!!!");
            }
        });

        before("/hello", (request, response) -> response.header("Foo", "Set by second before filter"));

        get("/hello", (request, response) -> "Hello World!");

        after("/hello", (request, response) -> response.header("spark", "added by after-filter"));
    }
}

Example showing how to use attributes

import static spark.Spark.after;
import static spark.Spark.get;

/**
 * Example showing the use of attributes
 */
public class FilterExampleAttributes {

    public static void main(String[] args) {
        get("/hi", (request, response) -> {
            request.attribute("foo", "bar");
            return null;
        });

        after("/hi", (request, response) -> {
            for (String attr : request.attributes()) {
                System.out.println("attr: " + attr);
            }
        });

        after("/hi", (request, response) -> {
            Object foo = request.attribute("foo");
            response.body(asXml("foo", foo));
        });
    }

    private static String asXml(String name, Object value) {
        return "<?xml version=\"1.0\" encoding=\"UTF-8\"?><" + name +">" + value + "</"+ name + ">";
    }
}

Example showing how to serve static resources

import static spark.Spark.*;

public class StaticResources {

    public static void main(String[] args) {

        // Will serve all static file are under "/public" in classpath if the route isn't consumed by others routes.
        // When using Maven, the "/public" folder is assumed to be in "/main/resources"
        staticFileLocation("/public");

        get("/hello", (request, response) -> "Hello World!");
    }
}

Example showing how to define content depending on accept type

import static spark.Spark.*;

public class JsonAcceptTypeExample {

    public static void main(String args[]) {

        //Running curl -i -H "Accept: application/json" http://localhost:4567/hello json message is read.
        //Running curl -i -H "Accept: text/html" http://localhost:4567/hello HTTP 404 error is thrown.
        get("/hello", "application/json", (request, response) -> "{\"message\": \"Hello World\"}");
    }
} 

Example showing how to render a view from a template. Note that we are using ModelAndView class for setting the object and name/location of template.

First of all we define a class which handles and renders output depending on template engine used. In this case FreeMarker.

public class FreeMarkerTemplateEngine extends TemplateEngine {

    private Configuration configuration;

    protected FreeMarkerTemplateEngine() {
        this.configuration = createFreemarkerConfiguration();
    }

    @Override
    public String render(ModelAndView modelAndView) {
        try {
            StringWriter stringWriter = new StringWriter();

            Template template = configuration.getTemplate(modelAndView.getViewName());
            template.process(modelAndView.getModel(), stringWriter);

            return stringWriter.toString();
        } catch (IOException e) {
            throw new IllegalArgumentException(e);
        } catch (TemplateException e) {
            throw new IllegalArgumentException(e);
        }
    }

    private Configuration createFreemarkerConfiguration() {
        Configuration retVal = new Configuration();
        retVal.setClassForTemplateLoading(FreeMarkerTemplateEngine.class, "freemarker");
        return retVal;
    }
}

Then we can use it to generate our content. Note how we are setting model data and view name. Because we are using FreeMarker, in this case a Map and the name of the template is required:

public class FreeMarkerExample {

    public static void main(String args[]) {

        get("/hello", (request, response) -> {
            Map<String, Object> attributes = new HashMap<>();
            attributes.put("message", "Hello FreeMarker World");

            // The hello.ftl file is located in directory:
            // src/test/resources/spark/examples/templateview/freemarker
            return new ModelAndView(attributes, "hello.ftl");
        }, new FreeMarkerTemplateEngine());
    }
}

Example of using Transformer.

First of all we define the transformer class, in this case a class which transforms an object to JSON format using gson API.

public class JsonTransformer implements ResponseTransformer {

    private Gson gson = new Gson();

    @Override
    public String render(Object model) {
        return gson.toJson(model);
    }
}

And then the code which return a simple POJO to be transformed to JSON:

public class TransformerExample {

    public static void main(String args[]) {
        get("/hello", "application/json", (request, response) -> {
            return new MyMessage("Hello World");
        }, new JsonTransformer());
    }
}
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