Создайте Java RESTful Client с помощью Jersey Client

1- The objective of the document

В данной статье я покажу вам как создать приложение Java RESTful Client используя  Jersey Client API чтобы вызвать  RESTful web service.
Примеры в данной статье ссылаются на  RESTful Web service в предыдущем руководстве, можете посмотреть по данной ссылке:

2- Create Maven Project

Удостоверьтесь что ваш project использует Java >=6, потому что в данном project используется библиотека  JAXB, имеющаяся в  Jdk6 или более обновленный.
Project Properties:
Объявить библиотеку  Jersey Client:
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
    http://maven.apache.org/xsd/maven-4.0.0.xsd">
    
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.o7planning</groupId>
    <artifactId>JerseyRESTClient</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>JerseyRESTClient</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
    
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>


        <!-- https://mvnrepository.com/artifact/com.sun.jersey/jersey-client -->
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-client</artifactId>
            <version>1.19.2</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.sun.jersey/jersey-json -->
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-json</artifactId>
            <version>1.19.2</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.sun.jersey/jersey-bundle -->
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-bundle</artifactId>
            <version>1.19.2</version>
        </dependency>

    </dependencies>
    
</project>

3- Model Classes

По умолчанию  Jersey API использует  JAXB это  XML-Binding по умолчанию, использующийся для конвертации объектов Java в XML и обратно, вы прикрепляете  Annotation в  JAXB к классам  model для аннотирования конвертации для JAXB.

И  MOXy является  JSON-Binding по умолчанию, чтобы  Jersey конвертировал объекты JSON в Java и обратно, вам не нужно прикреплять  Annotation к классам  model.
 
Employee.java
package org.o7planning.jerseyrestclient.model;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee {

  private String empNo;
  private String empName;
  private String position;

  // This default constructor is required if there are other constructors.
  public Employee() {

  }

  public Employee(String empNo, String empName, String position) {
      this.empNo = empNo;
      this.empName = empName;
      this.position = position;
  }

  public String getEmpNo() {
      return empNo;
  }

  public void setEmpNo(String empNo) {
      this.empNo = empNo;
  }

  public String getEmpName() {
      return empName;
  }

  public void setEmpName(String empName) {
      this.empName = empName;
  }

  public String getPosition() {
      return position;
  }

  public void setPosition(String position) {
      this.position = position;
  }


}

4- Get JSON to String

Пример ниже создает класс, который вызывает RESTful Web Serivce чтобы получить данные в виде  JSON, результат возвращает  String.
GetJsonAsString.java
package org.o7planning.jerseyrestclient;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class GetJsonAsString {

 public static void main(String[] args) {

     // Create Client
     Client client = Client.create();

     WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees/E01");

     ClientResponse response = webResource.accept("application/json").get(ClientResponse.class);

     // Status 200 is successful.
     if (response.getStatus() != 200) {
         System.out.println("Failed with HTTP Error code: " + response.getStatus());
         String error= response.getEntity(String.class);
         System.out.println("Error: "+error);
         return;
     }

     String output = response.getEntity(String.class);

     System.out.println("Output from Server .... \n");
     System.out.println(output);
 }

}

5- Get JSON to Object

В примере ниже  Jersey Client конвертирует данные  JSON в объекты  Java.
GetJsonAsObject.java
package org.o7planning.jerseyrestclient;

import javax.ws.rs.core.MediaType;

import org.o7planning.jerseyrestclient.model.Employee;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.WebResource.Builder;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;
import com.sun.jersey.api.json.JSONConfiguration;

public class GetJsonAsObject {

  public static void main(String[] args) {

      ClientConfig clientConfig = new DefaultClientConfig();

      // Create Client based on Config
      Client client = Client.create(clientConfig);

      WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees/E01");

      Builder builder = webResource.accept(MediaType.APPLICATION_JSON) //
              .header("content-type", MediaType.APPLICATION_JSON);

      ClientResponse response = builder.get(ClientResponse.class);

      // Status 200 is successful.
      if (response.getStatus() != 200) {
          System.out.println("Failed with HTTP Error code: " + response.getStatus());
         String error= response.getEntity(String.class);
         System.out.println("Error: "+error);
          return;
      }

      System.out.println("Output from Server .... \n");

      Employee employee = (Employee) response.getEntity(Employee.class);

      System.out.println("Emp No .... " + employee.getEmpNo());
      System.out.println("Emp Name .... " + employee.getEmpName());
      System.out.println("Position .... " + employee.getPosition());

  }

}

6- Get JSON to List

Jersey может конвертировать  JSON в List.
Например,  RESTful Web Service возвращает  List объектов.
@Path("/employees")
public class EmployeeService {

   // URI:
   // /contextPath/servletPath/employees
   @GET
   @Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML })
   public List<Employee> getEmployees() {
       List<Employee> listOfCountries = EmployeeDAO.getAllEmployees();
       return listOfCountries;
   }

}
Пример  Client:
GetJsonAsList.java
package org.o7planning.jerseyrestclient;

import java.util.List;

import javax.ws.rs.core.MediaType;

import org.o7planning.jerseyrestclient.model.Employee;

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.client.WebResource.Builder;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;

public class GetJsonAsList {

  public static void main(String[] args) {

      ClientConfig clientConfig = new DefaultClientConfig();

      // Create Client based on Config
      Client client = Client.create(clientConfig);

      WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees");

      Builder builder = webResource.accept(MediaType.APPLICATION_JSON) //
              .header("content-type", MediaType.APPLICATION_JSON);

      ClientResponse response = builder.get(ClientResponse.class);

      // Status 200 is successful.
      if (response.getStatus() != 200) {
          System.out.println("Failed with HTTP Error code: " + response.getStatus());
         String error= response.getEntity(String.class);
         System.out.println("Error: "+error);
          return;
      }

      GenericType<List<Employee>> generic = new GenericType<List<Employee>>() {
          // No thing
      };

      List<Employee> list = response.getEntity(generic);

      System.out.println("Output from Server .... \n");

      for (Employee emp : list) {
          System.out.println(" --- ");
          System.out.println("Emp No .... " + emp.getEmpNo());
          System.out.println("Emp Name .... " + emp.getEmpName());
          System.out.println("Position .... " + emp.getPosition());
      }

  }

}
Запуск примера:

7- Get XML to String

GetXmlAsString.java
package org.o7planning.jerseyrestclient;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class GetXmlAsString {

  public static void main(String[] args) {

      // Create Client
      Client client = Client.create();

      WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees/E01");

      ClientResponse response = webResource.accept("application/xml").get(ClientResponse.class);

      // Status 200 is successful.
      if (response.getStatus() != 200) {
          System.out.println("Failed with HTTP Error code: " + response.getStatus());
         String error= response.getEntity(String.class);
         System.out.println("Error: "+error);
          return;
      }

      String output = response.getEntity(String.class);

      System.out.println("Output from Server .... \n");
      System.out.println(output);
  }

}

8- Get XML to Object

GetXmlAsObject.java
package org.o7planning.jerseyrestclient;

import javax.ws.rs.core.MediaType;

import org.o7planning.jerseyrestclient.model.Employee;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.WebResource.Builder;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;

public class GetXmlAsObject {

  public static void main(String[] args) {

      ClientConfig clientConfig = new DefaultClientConfig();

      // Create Client based on Config
      Client client = Client.create(clientConfig);

      WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees/E01");

      Builder builder = webResource.accept(MediaType.APPLICATION_XML) //
              .header("content-type", MediaType.APPLICATION_XML);

      ClientResponse response = builder.get(ClientResponse.class);

      // Status 200 is successful.
      if (response.getStatus() != 200) {
          System.out.println("Failed with HTTP Error code: " + response.getStatus());
         String error= response.getEntity(String.class);
         System.out.println("Error: "+error);
          return;
      }

      System.out.println("Output from Server .... \n");

      Employee employee = (Employee) response.getEntity(Employee.class);

      System.out.println("Emp No .... " + employee.getEmpNo());
      System.out.println("Emp Name .... " + employee.getEmpName());
      System.out.println("Position .... " + employee.getPosition());

  }

}

9- Get XML to List

Пример  RESTful Web Service возвращает  List объектов.
 
@Path("/employees")
public class EmployeeService {

  // URI:
  // /contextPath/servletPath/employees
  @GET
  @Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML })
  public List<Employee> getEmployees() {
      List<Employee> listOfCountries = EmployeeDAO.getAllEmployees();
      return listOfCountries;
  }

}
GetXmlAsList.java
package org.o7planning.jerseyrestclient;

import java.util.List;

import javax.ws.rs.core.MediaType;

import org.o7planning.jerseyrestclient.model.Employee;

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.client.WebResource.Builder;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;

public class GetXmlAsList {

   public static void main(String[] args) {

       ClientConfig clientConfig = new DefaultClientConfig();

       // Create Client based on Config
       Client client = Client.create(clientConfig);

       WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees");

       Builder builder = webResource.accept(MediaType.APPLICATION_XML) //
               .header("content-type", MediaType.APPLICATION_XML);

       ClientResponse response = builder.get(ClientResponse.class);

       // Status 200 is successful.
       if (response.getStatus() != 200) {
           System.out.println("Failed with HTTP Error code: " + response.getStatus());
         String error= response.getEntity(String.class);
         System.out.println("Error: "+error);
           return;
       }

       GenericType<List<Employee>> generic = new GenericType<List<Employee>>() {
           // No thing
       };

       List<Employee> list = response.getEntity(generic);

       System.out.println("Output from Server .... \n");

       for (Employee emp : list) {
           System.out.println(" --- ");
           System.out.println("Emp No .... " + emp.getEmpNo());
           System.out.println("Emp Name .... " + emp.getEmpName());
           System.out.println("Position .... " + emp.getPosition());
       }

   }

}

10- Post JSON

Используя  POST сделать запрос  Web serivce чтобы создать новый рес. В примере ниже создается запрос  POST отправленный с данными  JSON чтобы сделать запрос создать новый  Employee.
PostJsonString.java
package org.o7planning.jerseyrestclient;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class PostJsonString {

    public static void main(String[] args) {

        Client client = Client.create();

        WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees");

        // Data send to web service.
        String input = "{\"empNo\":\"E01\",\"empName\":\"New Emp1\",\"position\":\"Manager\"}";

       
        ClientResponse response = webResource.type("application/json").post(ClientResponse.class, input);

        if (response.getStatus() != 200) {
            System.out.println("Failed : HTTP error code : " + response.getStatus());
           
            String error= response.getEntity(String.class);
            System.out.println("Error: "+error);
            return;
        }

        System.out.println("Output from Server .... \n");
       
        String output = response.getEntity(String.class);
       
        System.out.println(output);

    }

}
Запуск примера:
Jersey Client может автоматически конвертировать объект Java в JSON или  XML чтобы отправить с запросом.
PostJsonObject.java
package org.o7planning.jerseyrestclient;

import org.o7planning.jerseyrestclient.model.Employee;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class PostJsonObject {

    public static void main(String[] args) {

        Client client = Client.create();

        WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees");

        // This object will be automatically converted into JSON
        Employee newEmp = new Employee("E05", "New Emp1", "Manager");

        ClientResponse response = webResource.type("application/json").post(ClientResponse.class, newEmp);

        if (response.getStatus() != 200) {
            System.out.println("Failed : HTTP error code : " + response.getStatus());

            String error = response.getEntity(String.class);
            System.out.println("Error: " + error);
            return;
        }

        System.out.println("Output from Server .... \n");

        String output = response.getEntity(String.class);

        System.out.println(output);

    }

}

11- Post XML

PostXmlString.java
package org.o7planning.jerseyrestclient;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class PostXmlString {

  public static void main(String[] args) {

      Client client = Client.create();

      WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees");

      // Data send to web service.
      String input = "<employee>"//
                      + "<empNo>E05</empNo>"//
                      + "<empName>New Emp1</empName>"//
                      + "<position>Manager</position>"
                      + "</employee>";

       // Send XML and receive XML
       ClientResponse response = webResource.type("application/xml")//
               .accept("application/xml")//
               .post(ClientResponse.class, input);

      if (response.getStatus() != 200) {
          System.out.println("Failed : HTTP error code : " + response.getStatus());

          String error = response.getEntity(String.class);
          System.out.println("Error: " + error);
          return;
      }

      System.out.println("Output from Server .... \n");

      String output = response.getEntity(String.class);

      System.out.println(output);

  }

}
Jersey Client может автоматичкски конвертировать объект Java в JSON или  XML чтобы отправить с запросом.
 
PostXmlObject.java
package org.o7planning.jerseyrestclient;

import org.o7planning.jerseyrestclient.model.Employee;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class PostXmlObject {

    public static void main(String[] args) {

        Client client = Client.create();

        WebResource webResource = client.resource("http://localhost:8080/RESTfulCRUD/rest/employees");

        // This object will be automatically converted into XML
        Employee newEmp = new Employee("E05", "New Emp1", "Manager");

        // Send XML and receive XML
        ClientResponse response = webResource.type("application/xml")//
                .accept("application/xml") //
                .post(ClientResponse.class, newEmp);

        if (response.getStatus() != 200) {
            System.out.println("Failed : HTTP error code : " + response.getStatus());

            String error = response.getEntity(String.class);
            System.out.println("Error: " + error);
            return;
        }

        System.out.println("Output from Server .... \n");

        String output = response.getEntity(String.class);

        System.out.println(output);

    }

}