CS 185C/286 - Lecture 16

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Cay S. Horstmann

Lecture 16 Quiz 1

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Today's Lecture/Lab

Server-side programming
REST
JAX-RS
JAXB

REST

Client-server interface
Classic model: Remote procedure call (SOAP)
REST is stateless, cacheable
REST verbs: GET, POST, PUT, DELETE
REST API uses resource IDs that are revealed by the application (“hypertext model”)
REST URLs often look like http://api.fred.com/query/param

JAX-RS

Lets you build REST apps in Java
Needs a Java app server (e.g. GlassFish) or web profile bits and pieces
Can convert between Java objects/XML/JSON (via JAXB)

Hello, World!

import javax.ws.rs.*;
import javax.ws.rs.core.*;

@Path("/hello")
public class HelloService {
   @GET
   @Path("/{name}")
   public Response getText(@PathParam("name") String name) {
      String output = "Hello " + name + "\n";
      return Response.status(200).entity(output).build();
   }
}

JAXB

import javax.xml.bind.annotation.*;

@XmlRootElement
public class Person {
   private String name;
   
   public String getName() { return name; }
   public void setName(String newValue) { name = newValue; }
}

Automatically turns into <name>Fred</name> or {"name": "Fred" }

Reading Before Next Class

Chapter 9 in the Java EE Pocket Guide

Lab

A RESTful Service

Run curl https://api.github.com/users/cayhorstmann/events. What happens?
Run curl -i https://api.github.com/users/cayhorstmann/events. What is the content type?

Hello, World

Download Glassfish. Choose Full Platform/English/Zip archive
Unzip into your home directory
Run ~/glassfish-3.1.2.2/glassfish/bin/asadmin start-domain
Point your web browser to http://localhost:8080. What happens?
In your workspace directory, run mkdir -p lab16/WEB-INF/classes
Place the HelloService class into the workspace/lab16 directory

Also place the following class there:

import java.util.*;
import javax.ws.rs.*;
import javax.ws.rs.core.*;

@ApplicationPath("/rest")
public class AppConfig extends Application {

   public Set<Class<?>> getClasses() {
      return new java.util.HashSet<Class<?>>(Arrays.asList(HelloService.class));
   }
}

Run javac -d WEB-INF/classes -cp .:~/glassfish-3.1.2.2/glassfish/modules/\* *.java
Run jar cvfM ~/glassfish-3.1.2.2/glassfish/domains/domain1/autodeploy/greeting.war WEB-INF/classes/*
Point your browser to http://localhost:8080/greeting/rest/hello/World. What happens?
Why 8080? Why greeting? Why rest? Why hello?
What happens with World?

Media Type

Add @Produces("text/plain") to the getText message, and add the following method:

   @GET
   @Path("/{name}")
   @Produces("application/xml")
   public Response getXML(@PathParam("name") String name) {
      String output = "<hello>" + name + "</hello>\n";
      return Response.status(200).entity(output).build();
   }

Recompile and redeploy. Run

curl -H "Accept: text/plain" localhost:8080/greeting/rest/hello/World
curl -H "Accept: application/xml" localhost:8080/greeting/rest/hello/World

What happens?

Try getting text/html. What happens?
Add support for HTML. Simply return something like <body><h1>Hello</h1><h2>...</h2></body>. What did you do?
Now what happens when you curl for text/html?
What happens when you point your browser to localhost:8080/greeting/rest/hello/World?

XML and JSON

Add the Person class to the lab16 directory. Also add this class:

import javax.xml.bind.annotation.*;

@XmlRootElement
public class Greeting {
   private String message;
   private Person greeted;
   
   public String getMessage() { return message; }
   public void setMessage(String newValue) { message = newValue; }

   public Person getGreeted() { return greeted; }
   public void setGreeted(Person newValue) { greeted = newValue; }
}

In the getXML method, change output to an object of type Greeting. Make a Person, set its name, set it as the greeted one, and set message to "Hello". Compile and deploy.
What do you get from curl -H "Accept: application/xml" localhost:8080/greeting/rest/hello/World?
Add ,application/json to the @Produces annotation. Compile and deploy. set the header to Accept: application/json. What happens?
Are you impressed?