RESTful Web 服务 - 方法

正如目前为止我们所讨论的，RESTful Web 服务大量使用 HTTP 动词确定要对指定资源进行的操作。下面的表格演示了常用 HTTP 动词的例子。

编号HTTP 方法，URI 和操作1GET  http://localhost:8080/UserManagement/rest/UserService/users  获取用户列表  （只读）2GET  http://localhost:8080/UserManagement/rest/UserService/users/1  获取 ID 为 1 的用户  (只读)3PUT  http://localhost:8080/UserManagement/rest/UserService/users/2  插入 ID 为 2 的用户  （幂等）4POST  http://localhost:8080/UserManagement/rest/UserService/users/2  更新 ID 为 2 的用户  (N/A)5DELETE  http://localhost:8080/UserManagement/rest/UserService/users/1  删除 ID 为 1 的用户  （幂等）6OPTIONS  http://localhost:8080/UserManagement/rest/UserService/users  列出 Web 服务所支持的操作  （只读）7HEAD  http://localhost:8080/UserManagement/rest/UserService/users  只返回 HTTP 头，不返回 HTTP 体  （只读）

这里是要考虑的要点：

GET 操作是只读且安全的。PUT 和 DELETE 操作是幂等的意味着它们的结果总是相同的，无论这个操作被调用多少次。PUT 和 POST 操作几乎是相同的，区别在于 PUT 操作的结果是幂等的，而 POST 操作会导致不同的结果。

示例

让我们更新一下 RESTful Web 服务 - 第一个应用 教程中创建的例子来创建一个可以执行 CRUD（创建，读取，更新，移除）操作的 Web 服务。简单起见，这里我们使用文件 I/O 替代数据库操作。

我们来更新一下 com.tutorialspoint 包下面的 User.java，UserDao.java 和 UserService.java 文件。

User.java

package com.tutorialspoint; import java.io.Serializable; import javax.xml.bind.annotation.XmlElement; import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement(name = "user") public class User implements Serializable { private static final long serialVersionUID = 1L; private int id; private String name; private String profession; public User(){} public User(int id, String name, String profession){ this.id = id; this.name = name; this.profession = profession; } public int getId() { return id; } @XmlElement public void setId(int id) { this.id = id; } public String getName() { return name; } @XmlElement public void setName(String name) { this.name = name; } public String getProfession() { return profession; } @XmlElement public void setProfession(String profession) { this.profession = profession; } @Override public boolean equals(Object object){ if(object == null){ return false; }else if(!(object instanceof User)){ return false; }else { User user = (User)object; if(id == user.getId() && name.equals(user.getName()) && profession.equals(user.getProfession()) ){ return true; } } return false; } }

UserDao.java

package com.tutorialspoint; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.ArrayList; import java.util.List; public class UserDao { public List<User> getAllUsers(){ List<User> userList = null; try { File file = new File("Users.dat"); if (!file.exists()) { User user = new User(1, "Mahesh", "Teacher"); userList = new ArrayList<User>(); userList.add(user); saveUserList(userList); } else{ FileInputStream fis = new FileInputStream(file); ObjectInputStream ois = new ObjectInputStream(fis); userList = (List<User>) ois.readObject(); ois.close(); } } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } return userList; } public User getUser(int id){ List<User> users = getAllUsers(); for(User user: users){ if(user.getId() == id){ return user; } } return null; } public int addUser(User pUser){ List<User> userList = getAllUsers(); boolean userExists = false; for(User user: userList){ if(user.getId() == pUser.getId()){ userExists = true; break; } } if(!userExists){ userList.add(pUser); saveUserList(userList); return 1; } return 0; } public int updateUser(User pUser){ List<User> userList = getAllUsers(); for(User user: userList){ if(user.getId() == pUser.getId()){ int index = userList.indexOf(user); userList.set(index, pUser); saveUserList(userList); return 1; } } return 0; } public int deleteUser(int id){ List<User> userList = getAllUsers(); for(User user: userList){ if(user.getId() == id){ int index = userList.indexOf(user); userList.remove(index); saveUserList(userList); return 1; } } return 0; } private void saveUserList(List<User> userList){ try { File file = new File("Users.dat"); FileOutputStream fos; fos = new FileOutputStream(file); ObjectOutputStream oos = new ObjectOutputStream(fos); oos.writeObject(userList); oos.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }

UserService.java

package com.tutorialspoint; import java.io.IOException; import java.util.List; import javax.servlet.http.HttpServletResponse; import javax.ws.rs.Consumes; import javax.ws.rs.DELETE; import javax.ws.rs.FormParam; import javax.ws.rs.GET; import javax.ws.rs.OPTIONS; import javax.ws.rs.POST; import javax.ws.rs.PUT; import javax.ws.rs.Path; import javax.ws.rs.PathParam; import javax.ws.rs.Produces; import javax.ws.rs.core.Context; import javax.ws.rs.core.MediaType; @Path("/UserService") public class UserService { UserDao userDao = new UserDao(); private static final String SUCCESS_RESULT="<result>success</result>"; private static final String FAILURE_RESULT="<result>failure</result>"; @GET @Path("/users") @Produces(MediaType.APPLICATION_XML) public List<User> getUsers(){ return userDao.getAllUsers(); } @GET @Path("/users/{userid}") @Produces(MediaType.APPLICATION_XML) public User getUser(@PathParam("userid") int userid){ return userDao.getUser(userid); } @PUT @Path("/users") @Produces(MediaType.APPLICATION_XML) @Consumes(MediaType.APPLICATION_FORM_URLENCODED) public String createUser(@FormParam("id") int id, @FormParam("name") String name, @FormParam("profession") String profession, @Context HttpServletResponse servletResponse) throws IOException{ User user = new User(id, name, profession); int result = userDao.addUser(user); if(result == 1){ return SUCCESS_RESULT; } return FAILURE_RESULT; } @POST @Path("/users") @Produces(MediaType.APPLICATION_XML) @Consumes(MediaType.APPLICATION_FORM_URLENCODED) public String updateUser(@FormParam("id") int id, @FormParam("name") String name, @FormParam("profession") String profession, @Context HttpServletResponse servletResponse) throws IOException{ User user = new User(id, name, profession); int result = userDao.updateUser(user); if(result == 1){ return SUCCESS_RESULT; } return FAILURE_RESULT; } @DELETE @Path("/users/{userid}") @Produces(MediaType.APPLICATION_XML) public String deleteUser(@PathParam("userid") int userid){ int result = userDao.deleteUser(userid); if(result == 1){ return SUCCESS_RESULT; } return FAILURE_RESULT; } @OPTIONS @Path("/users") @Produces(MediaType.APPLICATION_XML) public String getSupportedOperations(){ return "<operations>GET, PUT, POST, DELETE</operations>"; } }

现在，使用 Eclipse 将你的应用程序导出为 war 文件然后部署到 Tomcat 中。要使用 eclipse 创建 WAR 文件，遵循选项 File -> export -> Web -> War File，最后选择项目 UserManagement 和目标文件夹即可。要在 Tomcat 中部署 war 文件，把 UserManagement.war 放到 Tomcat 安装目录 下的 webapps 目录中并启动 Tomcat 即可。

测试 Web 服务

Jersey 提供了创建 Web 服务客户端的 API 以测试 Web 服务。我们在同一项目的 com.tutorialspoint 包下面创建了一个范例测试类 WebServiceTester.java。

WebServiceTester.java

package com.tutorialspoint; import java.util.List; import javax.ws.rs.client.Client; import javax.ws.rs.client.ClientBuilder; import javax.ws.rs.client.Entity; import javax.ws.rs.core.Form; import javax.ws.rs.core.GenericType; import javax.ws.rs.core.MediaType; public class WebServiceTester { private Client client; private String REST_SERVICE_URL = "http://localhost:8080/UserManagement/rest/UserService/users"; private static final String SUCCESS_RESULT="<result>success</result>"; private static final String PASS = "pass"; private static final String FAIL = "fail"; private void init(){ this.client = ClientBuilder.newClient(); } public static void main(String[] args){ WebServiceTester tester = new WebServiceTester(); //initialize the tester tester.init(); //test get all users Web Service Method tester.testGetAllUsers(); //test get user Web Service Method tester.testGetUser(); //test update user Web Service Method tester.testUpdateUser(); //test add user Web Service Method tester.testAddUser(); //test delete user Web Service Method tester.testDeleteUser(); } //Test: Get list of all users //Test: Check if list is not empty private void testGetAllUsers(){ GenericType<List<User>> list = new GenericType<List<User>>() {}; List<User> users = client .target(REST_SERVICE_URL) .request(MediaType.APPLICATION_XML) .get(list); String result = PASS; if(users.isEmpty()){ result = FAIL; } System.out.println("Test case name: testGetAllUsers, Result: " + result ); } //Test: Get User of id 1 //Test: Check if user is same as sample user private void testGetUser(){ User sampleUser = new User(); sampleUser.setId(1); User user = client .target(REST_SERVICE_URL) .path("/{userid}") .resolveTemplate("userid", 1) .request(MediaType.APPLICATION_XML) .get(User.class); String result = FAIL; if(sampleUser != null && sampleUser.getId() == user.getId()){ result = PASS; } System.out.println("Test case name: testGetUser, Result: " + result ); } //Test: Update User of id 1 //Test: Check if result is success XML. private void testUpdateUser(){ Form form = new Form(); form.param("id", "1"); form.param("name", "suresh"); form.param("profession", "clerk"); String callResult = client .target(REST_SERVICE_URL) .request(MediaType.APPLICATION_XML) .post(Entity.entity(form, MediaType.APPLICATION_FORM_URLENCODED_TYPE), String.class); String result = PASS; if(!SUCCESS_RESULT.equals(callResult)){ result = FAIL; } System.out.println("Test case name: testUpdateUser, Result: " + result ); } //Test: Add User of id 2 //Test: Check if result is success XML. private void testAddUser(){ Form form = new Form(); form.param("id", "2"); form.param("name", "naresh"); form.param("profession", "clerk"); String callResult = client .target(REST_SERVICE_URL) .request(MediaType.APPLICATION_XML) .put(Entity.entity(form, MediaType.APPLICATION_FORM_URLENCODED_TYPE), String.class); String result = PASS; if(!SUCCESS_RESULT.equals(callResult)){ result = FAIL; } System.out.println("Test case name: testAddUser, Result: " + result ); } //Test: Delete User of id 2 //Test: Check if result is success XML. private void testDeleteUser(){ String callResult = client .target(REST_SERVICE_URL) .path("/{userid}") .resolveTemplate("userid", 2) .request(MediaType.APPLICATION_XML) .delete(String.class); String result = PASS; if(!SUCCESS_RESULT.equals(callResult)){ result = FAIL; } System.out.println("Test case name: testDeleteUser, Result: " + result ); } }

现在，使用 Eclipse 运行这个测试。右击文件，遵循选项 Run as -> Java Application。在 Eclipse 控制台中我们会看到如下所示结果：

Test case name: testGetAllUsers, Result: pass Test case name: testGetUser, Result: pass Test case name: testUpdateUser, Result: pass Test case name: testAddUser, Result: pass Test case name: testDeleteUser, Result: pass