Retrofit restful client（二）基本例子

               

引入Retrofit

引入Retrofitt需要引入以下lib：

        <repositories>  <repository>   <id>maven-restlet</id>   <name>Public online Restlet repository</name>   <url>http://maven.restlet.org</url>  </repository> </repositories>

        <dependency>   <groupId>com.squareup.retrofit</groupId>   <artifactId>retrofit</artifactId>   <version>1.3.0</version>  </dependency>  <dependency>   <groupId>org.apache.httpcomponents</groupId>   <artifactId>httpcore</artifactId>   <version>4.3</version>  </dependency>  <dependency>   <groupId>org.apache.httpcomponents</groupId>   <artifactId>httpclient</artifactId>   <version>4.3.1</version>  </dependency>  <dependency>   <groupId>org.restlet.jee</groupId>   <artifactId>org.restlet</artifactId>   <version>${restlet.version}</version>  </dependency>  <!-- Jackson JSON Mapper -->  <dependency>   <groupId>org.codehaus.jackson</groupId>   <artifactId>jackson-mapper-asl</artifactId>   <version>1.9.13</version>  </dependency>  <dependency>

如果不是maven工程请下载以上的jar。

Retrofit转换器（JSON<->OBJECT）

通过转换器实现JSON和对象转换，无须手动编写大量业务源代码。REST的server的输入Object可以直接转换到Client的对象。

import java.io.IOException;public class JacksonConverter implements Converter { private final ObjectMapper objectMapper; public JacksonConverter(ObjectMapper objectMapper) {  this.objectMapper = objectMapper; } public Object fromBody(TypedInput body, Type type)   throws ConversionException {  JavaType javaType = objectMapper.getTypeFactory().constructType(type);  try {   return objectMapper.readValue(body.in(), javaType);  } catch (IOException e) {   throw new ConversionException(e);  } } public TypedOutput toBody(Object object) {  try {   String charset = "UTF-8";   return new JsonTypedOutput(objectMapper.writeValueAsString(object)     .getBytes(charset), charset);  } catch (IOException e) {   throw new AssertionError(e);  } } private static class JsonTypedOutput implements TypedOutput {  private final byte[] jsonBytes;  private final String mimeType;  public JsonTypedOutput(byte[] jsonBytes, String charset) {   this.jsonBytes = jsonBytes;   this.mimeType = "application/json; charset=" + charset;  }  public String fileName() {   return null;  }  public String mimeType() {   return mimeType;  }  public long length() {   return jsonBytes.length;  }  public void writeTo(OutputStream out) throws IOException {   out.write(jsonBytes);  } }}

实例Rest适配器

Rest适配器用于生成Rest interface service的源代码

    RestAdapter restAdapter = new RestAdapter.Builder().setServer("http://127.0.0.1:8080/rest").setConverter(converter).build();

建立Rest interface

   public interface TaskService{          @GET("/runtime/tasks")         DataResponse getTasks();   }

@GET：用的是Rest的get方法
DataRespone：是Rest的返回值

实例化interface并执行

   TaskService service=restAdapter.create(TaskService.class);   DataResponse dataResponse= service.getTasks();

完整的例子

   public class Simple {  public static void main(String[] args) throws Exception {  // Create our Converter  JacksonConverter converter = new JacksonConverter(new ObjectMapper());  RestAdapter restAdapter = new RestAdapter.Builder()    .setServer("http://localhost:8080/").setConverter(converter)    .build();                                 TaskService service=restAdapter.create(TaskService.class);                               DataResponse dataResponse= service.getTasks();                   } }

登陆（Activiti）

   String header="Basic " + Base64.encodeToString("kermit:kermit")

   @GET("/runtime/tasks")   DataResponse getTasks(@Header("Authorization") String header);