Spark - a tiny web framework for Java 8
Spark 2.9.3 is out!! Changeset
<dependency>
<groupId>com.sparkjava</groupId>
<artifactId>spark-core</artifactId>
<version>2.9.3</version>
</dependency>
Sponsor the project here https://github.com/sponsors/perwendel
For documentation please go to: http://sparkjava.com/documentation
For usage questions, please use stack overflow with the โspark-javaโ tag
Javadoc: http://javadoc.io/doc/com.sparkjava/spark-core
When committing to the project please use Spark format configured in https://github.com/perwendel/spark/blob/master/config/spark_formatter_intellij.xml
Getting started
<dependency>
<groupId>com.sparkjava</groupId>
<artifactId>spark-core</artifactId>
<version>2.9.2</version>
</dependency>
import static spark.Spark.*;
public class HelloWorld {
public static void main(String[] arg){
get("/hello", (request, response) -> "Hello World!");
}
}
View at: http://localhost:4567/hello
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 to port 5678 instead 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");
}
}
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 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;
}
}
}
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 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"));
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 "<?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 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());
}
}
Debugging
See Spark-debug-tools as a separate module.
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