Restlet学习：API使用

先上两张class hierarchy图：




把Restlet及子类理解成处理Http Request的东东，类似Servlet。把Representation及子类理解成Http Response的的展示对象。

(1). 作为Http Client使用。(类似Apache HttpClient，但这不是Restlet主要想提供的东东)
Client client = new Client(Protocol.HTTP);
//将http response打印到控制台
client.get("http://10.68.92.64").getEntity().write(System.out);

//另外的用法，构造request再发请求
Request request = new Request(Method.GET, "http://10.68.92.64");
Response response = client.handle(request);

Representation output = response.getEntity();
output.write(System.out);

(2). 作为Http Server使用。
1. 简单的http server.
//restlet可以理解成Servlet。（Restlet的名称估计来源于Servlet）
//任意请求都返回同样内容.
Restlet restlet = new Restlet() {
public void handle(Request request, Response response) {
response.setEntity("Hello World!", MediaType.TEXT_PLAIN);
}
};

//启动server，可以访问http://localhost:8182
new Server(Protocol.HTTP, 8182, restlet).start();

2. Component, Host, Application与Resource的关系与使用


Component component = new Component(); 

// 添加host 
component.getServers().add(Protocol.HTTP, 8182);

//attach application到host。在application可以attach多个resource。第一个参数对应url中的路径，如果没有表示是根路径"/"
component.getDefaultHost().attach("app", new MyApplication());
//可以直接attach restlet instance
//component.getDefaultHost().attach(restlet);

// Start the component. 
component.start();

//MyApplication类
public class MyApplication extends Application { 
 
    @Override 
    public Restlet createRoot() { 
        Router router = new Router(getContext());
        //第一个参数表示资源名，表示对该资源进行操作，url为/app/hello
        router.attach("/hello",MyResource.class); 
 
        return router; 
    } 
}

(3) 实现Resource
1. 简单的Resouce，只有http get的实现
public class MyResource extends Resource { 
 
    public MyResource(Context context, Request request, 
            Response response) { 
        super(context, request, response); 
 
        getVariants().add(new Variant(MediaType.TEXT_PLAIN)); 
    } 
 
    //get "http://host:port/app/hello"将调用该方法
    public Representation represent(Variant variant) { 
        Representation representation = new StringRepresentation( 
                "hello, world", MediaType.TEXT_PLAIN); 
        return representation; 
    } 
}

2. 其他http method的实现
//delete
public void removeRepresentations() throws ResourceException {...)
//put
public void storeRepresentation(Representation entity) {...}
//post
public void acceptRepresentation(Representation entity) {...}

(4) Router
MyApplication中已经使用过Router了，它的作用是映射url到restlet或resource


例如：
router.attach("/hello1", restlet1); 
router.attach("/hello2", restlet2); 
router.attach("/hello3", restlet3);


router.attach("/hello1", MyResource1.class); 
router.attach("/hello2", MyResource2.class); 
router.attach("/hello3", MyResource3.class);

(5) 将文件系统以web的方式发布
public static final String ROOT_URI = "file:///c:/restlet/docs/api/"; 
 
Application application = new Application() { 
    @Override 
    public Restlet createRoot() { 
        return new Directory(getContext(), ROOT_URI); 
    } 
}; 
 
component.getDefaultHost().attach("", application); 

(6) 给Http Server加上认证的功能


Guard也是Restlet的子类，相当于一个filter，处理request之前处理认证

@Override
public Restlet createRoot() {
Guard guard = new Guard(getContext(), 
ChallengeScheme.HTTP_BASIC, "title"); 
guard.getSecrets().put("user", "password".toCharArray()); 

Directory directory = new Directory(getContext(), ROOT_URI); 
guard.setNext(directory); 
return guard;
}

//request增加认证信息
ChallengeScheme scheme = ChallengeScheme.HTTP_BASIC; 
ChallengeResponse authentication = new ChallengeResponse(scheme, 
        "user", "password"); 
request.setChallengeResponse(authentication); 

(7) 重定向功能
Router router = new Router(getContext()); 
 
String target = "http://www.google.com/search?q={keywords}"; 
Redirector redirector = new Redirector(getContext(), target, 
        Redirector.MODE_CLIENT_TEMPORARY); 
 
Route route = router.attach("/search", redirector); 
 
// http://localhost:8182/search?kwd=myKeyword1+myKeyword2 
// 重定向到
// http://www.google.com/search?q=myKeyword1%20myKeyword2 
route.extractQuery("keywords", "kwd", true); 

参考：
http://www.restlet.org/documentation/