RESTful Web Services mit JAX-RS

Markus Boese & Mark Bonnekessel

9. Dezember 2014

Motivation REST JAX-RS Praktikum

Inhaltsverzeichnis

1 Motivation

2 REST

3 JAX-RS

4 Praktikum

Motivation REST JAX-RS Praktikum

Was ist JAX-RS?

• Java API for RESTful Web Services• GET http://api.example.com/students

[{

matrikelnummer: 1,name: "Hugo"

},{

matrikelnummer: 2,name: "Frank"

},{

matrikelnummer: 3,name: "Martin"

}]

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Motivation REST JAX-RS Praktikum

Einfaches Beispiel

@Path("students")public class StudentsRessource {

@GET@Produces(MediaType.APPLICATION_JSON)public List<Student> getStudents() {

List<Student> students = new ArrayList<Student>();

students.add(new Student(1,"Hugo"));students.add(new Student(2,"Frank"));students.add(new Student(3,"Martin"));

return students;}

}

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Motivation REST JAX-RS Praktikum

REST – Representational State Transfer

• REST 6= HTTP• Architekturstil fur verteilte Hypermedia-Systeme• RESTful Webservice• Gehort folgender Aufruf zu einer RESTful-API?

POSThttp://api.example.com/student/update?id=1&name=Max

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Motivation REST JAX-RS Praktikum

REST – Prinzipien

• Einteilung in Ressourcen• Einheitliche Operationen• Verschiedene Reprasentationen• Hypermedia as the Engine of Application State

(HATEOAS)• Stateless

Abbildung: Verknupfung von REST-Ressourcen (Eigene Darstellung).

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Motivation REST JAX-RS Praktikum

REST-Beispiel: HTTP

• Identifikation uber URIs:http://www.example.com/students

http://www.example.com/students?category=science

http://www.example.com/students/12345678

• Einheitlicher Operationen-Satz = HTTP-Methoden• Safe – Informationen empfangen, keine Seiteneffekte• Idempotent• HTTP-Statuscode

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Motivation REST JAX-RS Praktikum

HTTP-Methoden

Method Safe IdempotentOPTIONS X XGET X XHEAD X XPOSTDELETE XPUT X...

• Ressource ...• Anzeigen• Erstellen• Andern• Loschen

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Motivation REST JAX-RS Praktikum

REST – So nicht!

Abbildung: Twitters “REST” API(https://dev.twitter.com/rest/reference/post/statuses/destroy/%3Aid)

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Motivation REST JAX-RS Praktikum

JAX-RS

• Standard - JCP JSR 339 v2.0https://jcp.org/en/jsr/detail?id=339

• Jeresy 2.13 - JAX-RS Implementierung + Magic• https://github.com/jersey/jersey• Feb 2012 - Dec 2014 ca. 2.076 commits

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Motivation REST JAX-RS Praktikum

Annotation-Feuerwerk

• 28 Annotations• @GET, @POST, @DELETE, @PUT, @OPTIONS• @Path• @Produces, @Consumes• @Provider

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Motivation REST JAX-RS Praktikum

Jersey API - @GET I

@Path("students")public class StudentsRessource {

@GETpublic String getStudents() {

return "Homer Simpson, Gordon Freeman, LukeSkywalker"

}

@Postpublic String addStudent(...) {...

}

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Motivation REST JAX-RS Praktikum

Jersey API - @GET II

@Path("students")public class StudentsRessource {

@GETpublic Response getStudents() {

return Response.ok().entity("Homer Simpson,...").build()

}

@Postpublic String addStudent(...) {...

}

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Motivation REST JAX-RS Praktikum

Jersey API - @GET III

@Path("students")public class StudentsRessource {

@GET@Produces(MediaType.APPLICATION_JSON)public Response getStudents() {

String json = <Erzeuge Json z. B. GSON oderJackson>

return Response.ok().entity(json).build()}

@Postpublic String addStudent(...) {...

}

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Motivation REST JAX-RS Praktikum

Jersey API

• jersey-media-moxy• Jackson• JAXB

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Motivation REST JAX-RS Praktikum

Jersey API - Bean config

@XmlRootElement@XmlAccessorType(XmlAccessType.FIELD)public class Student {

private String name;

private int matrikelnummer;

public Student(){}

/* Getter / Setter */}

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Motivation REST JAX-RS Praktikum

Jersey API - @Produces I

@Path("students")public class StudentsRessource {

@GET@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public Response getStudents() {

Student student = new Student("Max Musterman",12345);

return Response.ok().entity(student).build()}

@Postpublic String addStudent(...) {...

}

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Motivation REST JAX-RS Praktikum

Jersey API - @Produces II

@Path("students")public class StudentsRessource {

@GET@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public List<Student> getStudents() {

List<Student> students = new ArrayList<Student>();

students.add(new Student(1,"Hugo"));students.add(new Student(2,"Frank"));students.add(new Student(3,"Martin"));

return students;}

}

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Motivation REST JAX-RS Praktikum

Grizzly Intern

Abbildung: https://grizzly.java.net/

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Motivation REST JAX-RS Praktikum

Fehlerbehandlung

@Providerpublic class ExceptionMapper implements

ExceptionMapper<Throwable>{

@Overridepublic Response toResponse(Throwable throwable){

// Log ExceptionHttpError error = new HttpError(500,

throwable.getMessage());return Response.status(error.getStatus()).

type(MediaType.APPLICATION_JSON).entity(error).build();

}}

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Motivation REST JAX-RS Praktikum

Jersey API - exception handling

@Path("students")public class StudentsRessource {

@GET@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public List<Student> getStudents() {

try {List<Student> students =

StudentDao.ladeStudenten(...);...return students;

} catch (Exception e) {throw new

WebApplicationException(Response.(...).build());}

}}

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Motivation REST JAX-RS Praktikum

Jersey API

@Path("students")public class StudentsRessource {

@GET@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public List<Student> getStudents() {

...}

@GET@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public Student getStudents(String name) {

...}

}

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Motivation REST JAX-RS Praktikum

Validierung

• Regulare Ausdrucke innerhalb einiger Annotations• Third Party Frameworks: Hibernate Validator - JSR 303

• Definition von weiteren Annotations• jersey-bean-validation

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Motivation REST JAX-RS Praktikum

Jersey API

@Path("Sub-Path/{variable: Regex Pattern}")

@Path("1/{name: [A-Za-zaous_]+}")<domain>/students/1/homer_simpson

@Path("{name: [A-Za-zaous_]+}")<domain>/students/homer_simpson

@Path("{id: [0-9]+}")<domain>/students/1234

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Motivation REST JAX-RS Praktikum

Jersey API

@Path("students")public class StudentsRessource {

@GET....

@GET@Path("{name: [A-Za-zaous]+}")@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public Student getStudents(String name) {

...}

}

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Motivation REST JAX-RS Praktikum

Jersey API

@Path("students")public class StudentsRessource {

@GET....

@GET@Path("1")@Produces({MediaType.APPLICATION_JSON,

MediaType.APPLICATION_XML})public Student getStudents(@QueryParam("name") String

name) {...

}}

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Motivation REST JAX-RS Praktikum

Jersey API - @Consumes

@Path("students")public class StudentsRessource {

@PUT@Path("{id}")@Consumes(MediaType.APPLICATION_JSON)@Produces(MediaType.APPLICATION_JSON)public Response updateArticle(

@PathParam("id") String id,Article article) {...

}}

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Motivation REST JAX-RS Praktikum

Cross-Origin Resource Sharing (CORS)

Nicht verletzt wenn Protokoll, Host und Port gleich sind.

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Motivation REST JAX-RS Praktikum

CORS - Server

Access-Control-Allow-Origin:http://localhost:8181

Access-Control-Allow-Headers:origin, content-type, accept, authorization

Access-Control-Allow-Credentials:true

Access-Control-Allow-Methods:GET, POST, PUT, DELETE, OPTIONS, HEAD

Access-Control-Max-Age:120

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Motivation REST JAX-RS Praktikum

CORS - Client

Origin:http://localhost:8181

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Motivation REST JAX-RS Praktikum

Client-API

Client client = ClientBuilder.newClient();target = client.target("http://www.localhost:8080/");

Response response = target.path("students").get();

Assert.assertEquals(Response.Status.OK.getStatusCode(),response.getStatus());

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Motivation REST JAX-RS Praktikum

MediaType

Client client = ClientBuilder.newClient();target = client.target("http://www.localhost:8080/");

Response response = target.path("students").request(MediaType.APPLICATION_JSON).get();

Assert.assertEquals(MediaType.APPLICATION_JSON,response.getMediaType().toString());

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Motivation REST JAX-RS Praktikum

JSON

Client client = ClientBuilder.newClient();target = client.target("http://www.localhost:8080/");

Response response = target.path("student").path("123").request(MediaType.APPLICATION_JSON).get();

Student student = response.readEntity(Student.class);

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Motivation REST JAX-RS Praktikum

Liste von JSON-Elementen

Client client = ClientBuilder.newClient();target = client.target("http://www.localhost:8080/");

Response response = target.path("students").request(MediaType.APPLICATION_JSON).get();

List<Article> students = response.readEntity(newGenericType<List<Article>>() {});

Assert.assertEquals(10, students.size());

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Motivation REST JAX-RS Praktikum

PUT

Student student = new Student();

response = target.path("students").path("123").request(MediaType.APPLICATION_JSON).put(Entity.entity(student,

MediaType.APPLICATION_JSON));

Assert.assertEquals(Response.Status.OK.getStatusCode(),response.getStatus());

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Motivation REST JAX-RS Praktikum

Praktikum

Demo

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LiteraturStefan Tilkov : REST und HTTP.Dpunkt-Verlag, Heidelberg, 2009

Online Quellen

• http://www.w3.org/Protocols/rfc2616/rfc2616.html• http://www.ics.uci.edu/˜fielding/pubs/

dissertation/rest_arch_style.htm• https://jersey.java.net/• https://grizzly.java.net/• https://developer.mozilla.org/en-US/docs/Web/

HTTP/Access_control_CORS• http://docs.oracle.com/javase/8/docs/api/