Introduction
REST(Representational State Transfer)是一種分散式超媒體系統(如WWW)的軟體架構風格,你可以想像它是一個良好設計的Web應用程式規則。
REST 所描述的網路系統包括三個部份:
- Data elements (resource, resource identifier, representation)
- Connectors (client, server, cache, resolver, tunnel)
- Domponents (origin server, gateway, proxy, user agent)
REST Principles
Data elements 由標準化介面存取
Components 透過介面傳輸 資源表徵 (representations of resources) 來溝通,而不是直接操作資源本身。
Connectors 提供 component 的抽象介面來溝通,隱藏溝通機制的實作細節。
REST符合以下幾個條件:
應用程式的狀態跟功能拆成 resources
每個 Resource 使用 URI 作為獨一無二的定址方式
所有 Resources 共用相同的介面在 Client 跟 Resource 之間轉換狀態,包括:
A. 定義操作 well-defined operations (在HTTP中即 GET/POST/PUT/DELETE)
B. 有限的內容格式 content types
REST包含以下特色:
A. Client/Server 架構
B. Stateless 狀態無關
C. Cacheable 快取能力
D. Layered 分層能力
符合 REST principles 的系統稱做 RESTful。
Lightweight REST framework, Restlet API
Restlet on Jetty Implement
載入相關Jar檔
- org.restlet.jar
- com.noelios.restlet.jar
- com.noelios.restlet.ext.servlet.jar
以Eclipse開啟Dynamic Web Project新專案
新增EntryApplication.java
package com.toright.rest; import org.restlet.Application; import org.restlet.Context; import org.restlet.Restlet; import org.restlet.Router; public class EntryApplication extends Application { public EntryApplication(Context parentContext) { super(parentContext); } @Override public synchronized Restlet createRoot() { Router router = new Router(getContext()); //設定URI位置 router.attach("/users/{user}", UserResource.class); //設定預設的處理Class router.attachDefault(HelloWorldResource.class); return router; } }
新增HelloWorldResource.java
package com.toright.rest; import org.restlet.Context; import org.restlet.data.MediaType; import org.restlet.data.Request; import org.restlet.data.Response; import org.restlet.resource.Representation; import org.restlet.resource.Resource; import org.restlet.resource.StringRepresentation; import org.restlet.resource.Variant; public class HelloWorldResource extends Resource { public HelloWorldResource(Context context, Request request, Response response) { super(context, request, response); getVariants().add(new Variant(MediaType.TEXT_PLAIN)); } @Override public Representation getRepresentation(Variant variant) { Representation representation = new StringRepresentation("Hello world", MediaType.TEXT_PLAIN); return representation; } }
新增UserResource.java
package com.toright.rest; import org.restlet.Context; import org.restlet.data.MediaType; import org.restlet.data.Request; import org.restlet.data.Response; import org.restlet.resource.Representation; import org.restlet.resource.Resource; import org.restlet.resource.StringRepresentation; import org.restlet.resource.Variant; public class UserResource extends Resource { String userName; Object user; public UserResource(Context context, Request request, Response response) { super(context, request, response); System.out.println("Method:"+request.getMethod().getName()); this.userName = (String) request.getAttributes().get("user"); getVariants().add(new Variant(MediaType.TEXT_PLAIN)); } @Override public Representation getRepresentation(Variant variant) { Representation result = null; if (variant.getMediaType().equals(MediaType.TEXT_PLAIN)) { result = new StringRepresentation("Account of user \"" + this.userName + "\""); } return result; } }
編輯 web.xml
first steps servlet org.restlet.application com.transtep.rest.EntryApplication RestletServlet com.noelios.restlet.ext.servlet.ServerServlet RestletServlet /*
專案的結構如下圖
執行Jetty與測試 http://127.0.0.1:8080/restlet/ 沒有輸入資源位置,自動轉換至預設處理Class,畫面顯示Hello,world
http://127.0.0.1:8080/restlet/users/mary 以資源位置處理相關的功能