Spark - a Sinatra inspired web framework

<dependency>
 <groupId>com.sparkjava</groupId>
 <artifactId>spark-core</artifactId>
 <version>2.3</version>
</dependency>

Getting started

import static spark.Spark.*;
public class HelloWorld {
 public static void main(String[] args) {
 get("/hello", (request, response) -> "Hello World!");
 }
}

mvn javadoc:javadoc

Examples

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 to port 5678 in stead of the default 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");
 }
}

import static spark.Spark.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
/**
 * A simple CRUD example showing how to 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 in the post body as x-www-urlencoded values e.g. author=Foo&title=Bar
 // you get them by using request.queryParams("valuename")
 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 in the request body as x-www-urlencoded values e.g. author=Foo&title=Bar
 // you get them by using request.queryParams("valuename")
 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 (ids)
 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;
 }
 }
}

import static spark.Spark.*;
import java.util.HashMap;
import java.util.Map;
/**
 * Example showing a very simple (and stupid) authentication 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"));
 }
}

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 + ">";
 }
}

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!");
 }
}

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\"}");
 }
} 

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;
 }
}

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());
 }
}

public class JsonTransformer implements ResponseTransformer {
	private Gson gson = new Gson();
	@Override
	public String render(Object model) {
		return gson.toJson(model);
	}
}

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