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A simple expressive web framework for java. Spark has a kotlin DSL https://github.com/perwendel/spark-kotlin
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perwendel/spark
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README.md
Spark — a tiny web framework for Java 8
Spark 2.9.4 is out!!
dependency> groupId>com.sparkjavagroupId> artifactId>spark-coreartifactId> version>2.9.4version> dependency>
dependency> groupId>com.sparkjavagroupId> artifactId>spark-coreartifactId> version>2.9.4version> dependency>
import static spark.Spark.*; public class HelloWorld < public static void main(String[] arg)< get("/hello", (request, response) -> "Hello World!"); > >
Check out and try the examples in the source code. You can also check out the javadoc. After getting the source from github run:
The result is put in /target/site/apidocs
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); 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 "\"1.0\" encoding=\"UTF-8\"?>" + request.params("section") + ""; >); 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 how to 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 how to create, get, update and delete book resources. */ public class Books < /** * Map holding the books */ private static MapString, Book> books = new HashMapString, 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; > > >
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) 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 MapString, String> usernamePasswords = new HashMapString, 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")); afterAfter("/hello", (request, response) -> response.header("finally", "executed even if exception is throw")); afterAfter((request, response) -> response.header("finally", "executed after any route even if exception is throw")); > >
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 "\"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) -> < MapString, 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 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()); > >
See Spark-debug-tools as a separate module.