用Java實現RESTful Web Services框架的簡要步驟
1、 REST和RESTful Web Services的簡要說明
REST(RepresentationalState Transfer),中文稱為表述性狀態轉移,是一種針對於網路應用開發的軟體架構風格,是滿足一定的架構約束條件的。REST包括的準則主要有:1)網路上所有事物都抽象成資源;2)每個資源對應唯一的URI;3)通過通用介面對資源操作;5)操作都是無狀態的;
RESTfulWeb Services,這是基於REST和HTTP實現的Web服務,在其實現的時候定義了URI,對資源的操作,以及支援的MIME型別等。
2、 JAX-RS和Jersey的簡要說明:
JAX-RS,或稱JSR311,是幫助實現RESTful WebServices的一組API,而Jersey則是其參考實現。
3、 開發環境配置:
Eclipse: 需要能進行Web Service開發的版本,例如《Eclipse IDE forJava EE Developers》,官網的下載地址附在部落格末尾;
Tomcat:Tomcat是作為Web應用程式的伺服器而使用的,為了在本次開發中能正確開發並除錯程式,需要在Eclipse上預先配置Tomcat,具體步驟給出了相關連結,不在博文內直接表述。Tomcat的下載版本也至於文末;
4、 Jersey開發包下載以及其它包下載:
為了開發RESTful Web服務,需要下載對應的Jersey庫檔案,同時在本程式中,由於需要採用JSON樣式,需要額外下載部分jar包;所有需要的jar包的截圖如下:
其中,Jersey相關庫檔案可從其官網下載,連結文末給出;其餘jar包也一起打包置於lib.rar中。
5、 具體步驟:
步驟一:新建Eclipse工程:“File->New->Other->DynamicWeb Project”,此處將工程命名為Jersey,之後的配置大約如下,具體需要注意Target runtime需要指定為對應的Tomcat版本,例如此處是7.0;
步驟二:將剛才下載的全部jar包複製到工程目錄下,WEB-INF資料夾下的lib中,如圖所示;
步驟三:新建包用於存放所有資源,此處命名為sample.hello.resources,並新建類HelloResource(此資源僅用於測試,之後可以刪除),程式碼如下:
package sample.hello.resources;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
@Path("/hello")
public class HelloResource {
@GET
@Produces(MediaType.TEXT_PLAIN)
public String sayHello() {
return "Hello Jersey";
}
}
其中,@Path即定義了資源的URI,@Get即HTTP的Get方法,@Produces聲明瞭相應內容的MIME型別;
步驟四:修改WEB-INF下的web.xml檔案,內容改為:
<?xml version="1.0" encoding="UTF-8"?>
Jerseyindex.htmlindex.htmindex.jspdefault.htmldefault.htmdefault.jspJersey REST Service
com.sun.jersey.spi.container.servlet.ServletContainer
com.sun.jersey.config.property.packagessample.hello.resources1Jersey REST Service/rest/*
之後就可以嘗試啟動Tomcat,並在瀏覽器中輸入:http://your_domain:port/display-name/url-pattern/path_from_rest_class以訪問資源了,例到目前為止,要訪問HelloResource則需要進入http://localhost:8080/Jersey/rest/hello.成功的話,則瀏覽器返回‘Hello Jersey’.
步驟五:接下來,以所謂聯絡人(Contacts)為樣例程式進行開發,主要的資源包括了ContactResource和ContactsResource兩種,後者是前者的資源集合;資源定義分別如下:
public class ContactResource {
@Context
UriInfo uriInfo;
@Context
Request request;
String contact;
public ContactResource(UriInfo uriInfo, Request request,
String contact) {
this.uriInfo = uriInfo;
this.request = request;
this.contact = contact;
}
@GET
@Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
public Contact getContact() {
Contact cont = ContactStore.getStore().get(contact);
if(cont==null)
throw new NotFoundException("No such Contact.");
return cont;
}
}
ContactsResource:
@Path("/contacts")
public class ContactsResource {
@Context
UriInfo uriInfo;
@Context
Request request;
@GET
@Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
public List getContacts() {
List contacts = >new ArrayList();
contacts.addAll( ContactStore.getStore().values() );
return contacts;
}
@Path("{contact}")
public ContactResource getContact(
@PathParam("contact") String contact) {
return new ContactResource(uriInfo, request, contact);
}
}
這樣就定義完樣例程式的資源了。在具體實現程式時應該根據需要定義資源的屬性和方法;
步驟六:上述僅僅實現了對資源的Get操作,即“檢索某一資源的表現形式”或“列出資源集合中的所有成員”,要實現POST(建立資源或子資源),PUT(更新資源),DELETE(刪除資源)操作,則需要在資源定義中宣告額外的方法。例如:
POST操作(建立一個Contact):
@POST
@Produces(MediaType.TEXT_HTML)
@Consumes(MediaType.APPLICATION_FORM_URLENCODED)
public void newContact(
@FormParam("id") String id,
@FormParam("name") String name,
@Context HttpServletResponse servletResponse
) throws IOException {
Contact c = new Contact(id,name,new ArrayList
());
ContactStore.getStore().put(id, c);
URI uri = uriInfo.getAbsolutePathBuilder().path(id).build();
Response.created(uri).build();
servletResponse.sendRedirect("../pages/new_contact.html");
}
PUT操作(更新一個Contact):
@PUT
@Consumes(MediaType.APPLICATION_XML)
public Response putContact(JAXBElement jaxbContact) {
Contact c = jaxbContact.getValue();
return putAndGetResponse(c);
}
private Response putAndGetResponse(Contact c) {
Response res;
if(ContactStore.getStore().containsKey(c.getId())) {
res = Response.noContent().build();
} else {
res = Response.created(uriInfo.getAbsolutePath()).build();
}
ContactStore.getStore().put(c.getId(), c);
return res;
}
DELETE(刪除一個Contact):
@DELETE
public void deleteContact() {
Contact c = ContactStore.getStore().remove(contact);
if(c==null)
throw new NotFoundException("No such Contact.");
}
步驟七(只針對樣例程式):這一步驟是為了實現資源的定義而附加的操作,與具體的Web服務有關。就樣例程式而言,這一步是必須的,但是對於其它程式則不是。在定義完成資源之後需要額外增加四個類的定義:位於sample.hello.bean下的Address類的定義和Contact類的定義,位於sample.hello.storage下的ContactStore,以及位於sample.hello.util下的ParamUtil類的定義。程式碼分別如下:
Address.java:
package sample.hello.bean;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Address {
private String city;
private String street;
public Address() {}
public Address(String city, String street) {
this.city = city;
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
}
Contact.java:
package sample.hello.bean;
import java.util.List;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Contact {
private String id;
private String name;
private List
addresses;
public Contact() {}
public Contact(String id, String name, List addresses) {
this.id = id;
this.name = name;
this.addresses = addresses;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@XmlElement(name="address")
public List getAddresses() {
return addresses;
}
public void setAddresses(List addresses) {
this.addresses = addresses;
}
}
ContactStore.java:
package sample.hello.storage;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import sample.hello.bean.Address;
import sample.hello.bean.Contact;
public class ContactStore {
private static Map store;
private static ContactStore instance = null;
private ContactStore() {
store = new HashMap();
initOneContact();
}
public static Map getStore() {
if(instance==null) {
instance = new ContactStore();
}
return store;
}
private static void initOneContact() {
Address[] addrs = {
new Address("Shanghai", "Long Hua Street"),
new Address("Shanghai", "Dong Quan Street")
};
Contact cHuang = new Contact("huangyim", "Huang Yi Ming", Arrays.asList(addrs));
store.put(cHuang.getId(), cHuang);
}
}
ParamUtil.java:
package sample.hello.util;
import java.util.HashMap;
import java.util.Map;
public class ParamUtil {
public static Map parse(String paramString) {
Map params = new HashMap();
String[] paramPairs = paramString.split("&");
for(String param : paramPairs) {
String[] key_value = param.split("=");
params.put(key_value[0], key_value[1]);
}
return params;
}
}
到此為止,樣例程式的資源定義就完成了。
步驟八(只針對樣例程式):此時啟動Tomcat並訪問ContactsResource資源,則可以看到一個Contact的JSON的樣式表現如下:
{"contact":{"address":[{"city":"Shanghai","street":"LongHua Street"},{"city":"Shanghai","street":"DongQuanStreet"}],"id":"huangyim","name":"HuangYi Ming"}}
步驟九(選做):通過Jersey Client可以與RESTful Web 服務通訊,這可以用於對服務進行單元測試(基於不同操作)。所需要完成的內容大概如下:
package sample.hello.client;
import java.util.Arrays;
import java.util.List;
import javax.ws.rs.core.MediaType;
import javax.xml.bind.JAXBElement;
import sample.hello.bean.Address;
import sample.hello.bean.Contact;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.GenericType;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.representation.Form;
public class ContactClient {
public static void main(String[] args) {
Client c = Client.create();
WebResource r = c.resource("http://localhost:8080/Jersey/rest/contacts");
System.out.println("===== Get huangyim =====");
getOneContact(r, "huangyim");
System.out.println("===== Create foo =====");
postForm(r, "foo", "bar");
Address[] addrs = {
new Address("Shanghai", "Ke Yuan Street")
};
Contact cnt = new Contact("guoqing", "Guo Qing", Arrays.asList(addrs));
System.out.println("===== Create guoqing =====");
putOneContact(r, cnt);
System.out.println("===== All Contacts =====");
getContacts(r);
System.out.println("===== Delete foo =====");
deleteOneContact(r, "foo");
System.out.println("===== All Contacts =====");
getContacts(r);
}
public static void getContacts(WebResource r) {
// 1, get response as plain text
String jsonRes = r.accept(MediaType.APPLICATION_JSON).get(String.class);
System.out.println(jsonRes);
String xmlRes = r.accept(MediaType.APPLICATION_XML).get(String.class);
System.out.println(xmlRes);
// 2, get response and headers etc, wrapped in ClientResponse
ClientResponse response = r.get(ClientResponse.class);
System.out.println( response.getStatus() );
System.out.println( response.getHeaders().get("Content-Type") );
String entity = response.getEntity(String.class);
System.out.println(entity);
// 3, get JAXB response
GenericType> genericType = new GenericType>() {};
List contacts = r.accept(MediaType.APPLICATION_JSON).get(genericType);
System.out.println("No. of Contacts: " + contacts.size());
Contact contact = contacts.get(0);
System.out.println(contact.getId() + ": " + contact.getName());
}
public static void getOneContact(WebResource r, String id) {
GenericType> generic = new GenericType>() {};
JAXBElement jaxbContact = r.path(id).accept(MediaType.APPLICATION_JSON).get(generic);
Contact contact = jaxbContact.getValue();
System.out.println(contact.getId() + ": " + contact.getName());
}
public static void postForm(WebResource r, String id, String name) {
Form form = new Form();
form.add("id", id);
form.add("name", name);
ClientResponse response = r.type(MediaType.APPLICATION_FORM_URLENCODED)
.post(ClientResponse.class, form);
System.out.println(response.getEntity(String.class));
}
public static void putOneContact(WebResource r, Contact c) {
ClientResponse response = r.path(c.getId()).accept(MediaType.APPLICATION_JSON)
.put(ClientResponse.class, c);
System.out.println(response.getStatus());
}
public static void deleteOneContact(WebResource r, String id) {
ClientResponse response = r.path(id).delete(ClientResponse.class);
System.out.println(response.getStatus());
}
}
以上便是用Java進行RESTful WebServices開發的全部內容。主要的工作在於對URI的定義和相關操作方法的定義。
附加連結:
1、 Eclipse 官網下載:http://www.eclipse.org/downloads/
2、 Tomcat官網下載:http://tomcat.apache.org/download-70.cgi
3、 在Eclipse上配置Tomcat: http://jingyan.baidu.com/article/ca2d939dd90183eb6d31ce79.html
4、 Jersey官網下載:https://jersey.java.net/download.html
5、 參考連結1:http://only81.iteye.com/blog/1689537
6、 參考連結2:http://hbluojiahui.blog.163.com/blog/static/310647672009823101440937/
7、 參考連結3:http://blog.csdn.net/zztfj/article/details/7608991