返回信息给Consumer

return four types of Java constructs:

common Java types return basic information with HTTP return codes determined by the JAX-RS runtime;
JAXB objects return complex information with HTTP return codes determined by the JAX-RS runtime;
JAX-RS Response objects return complex information with a programmatically determined HTTP return status. The Response object also allows HTTP headers to be specified;
JAX-RS GenericEntity objects return complex information with HTTP return codes determined by the JAX-RS runtime. The GenericEnitity object provides more information to the runtime components serializing the data.

1. Returning plain Java constructs

通常情况下，resource class返回一个标准的Java Type, 一个JAXB对象，或者任何的对象(应用程序有对应的Entity

Provider)；在这种情况下，运行环境将使用返回的对象来决定MIME type信息，运行环境也决定使用适合的HTTP

Code发送给Consumer.

(1) Returnable types: 可以是null或者是：Java 原生类型，Java原生类型的Numbet representations， JAXBObject.

(2) MIME types: 运行环境决定返回Entiy 的MIME type首先检查resource method 和 resource class的@Produce

注解；如果找到一个，将使用注解中指定的MIME type，如果没有找到，将依赖与Entity Provider来决定适合的

MIME Type.默认情况下，运行环境分配MIME Type按照下面的方式进行：

Java primitives 和她们的Number representations被赋予MIME Type:application/octet-stream;
JAXB objects被赋予MIME Type:application/xml.

(3) Response codes

如果resource method完成处理时没有抛出异常并且返回了Plain Java Constructs时，运行环境将自动设置response

status code:

204(No Content)—the resource method's return type is void
204(No Content)—the value of the returned entity is null
200(OK)—the value of the returned entity is not null

2. Basics of building responses

Response Object 包装了返回给Consumer的Entity，该对象使用ResponseBuilder工厂类进行实例化。

获取Reponse Builder: 有两种方法：

(1) 使用Response类的静态方法：

import javax.ws.rs.core.Response;

Response r = Response.ok().build();

(2) 使用ResponseBuilderImpl类

import javax.ws.rs.core.Response;
import org.apache.cxf.jaxrs.impl.ResponseBuilderImpl;

ResponseBuilderImpl builder = new ResponseBuilderImpl();
builder.status(200);
Response r = builder.build();

3. Creating responses for common use cases

(1) Creating responses for successful requests

例如：下面的例子返回HTTP Status 200并包含一个Entity:Customer:

import javax.ws.rs.core.Response;
import demo.jaxrs.server.Customer;

Customer customer = new Customer("Jane", 12);
return Response.ok(customer).build();

如果希望返回值是200，但没有Content,可以使用Response.noContent() method：

import javax.ws.rs.core.Response;

return Response.noContent().build();

(2) Creating responses for redirection

Response Class 提供了method用于处理redirection response statuses：

A. 303 See Other：当request resource需要用久的重定向consumer至一个新的resource时，使用Response类的

seeOther() method;

B. 304 Not Modified：当request resource没有改变时，使用notModified() method;

import javax.ws.rs.core.Response;

return Response.notModified().build();

C. 307 Temporary Redirect：当request resource需要引导consumer至一个新的resource，但是想consumer继续

使用这个resource来处理未来的request时，使用temporaryRedirect() method.

(3) Creating responses to signal errors

Response Class提供了类处理两个基本的Error:

A. serverError()(): Status of 500 Internal Server Error;

B. notAcceptable()(java.util.List<javax.ws.rs.core.Variant> variants): 创建一个Reponse，有406 Status Code和一

个Entity(包含a list of acceptable resource types).

import javax.ws.rs.core.Response;

return Response.serverError().build();

4. Handling more advanced responses

(1) Adding custom headers

import javax.ws.rs.core.Response;
import org.apache.cxf.jaxrs.impl.ResponseBuilderImpl;

ResponseBuilderImpl builder = new ResponseBuilderImpl();
builder.header("username", "joe");
Response r = builder.build();

(2) Adding a cookie

import javax.ws.rs.core.Response;
import javax.ws.rs.core.NewCookie;

NewCookie cookie = new NewCookie("username", "joe");
Response r = Response.ok().cookie(cookie).build();

(3) Setting the response status

import javax.ws.rs.core.Response;
import org.apache.cxf.jaxrs.impl.ResponseBuilderImpl;

ResponseBuilderImpl builder = new ResponseBuilderImpl();
builder.status(404);
Response r = builder.build();

(4) Setting cache control directives

import javax.ws.rs.core.Response;
import javax.ws.rs.core.CacheControl;
import org.apache.cxf.jaxrs.impl.ResponseBuilderImpl;

CacheControl cache = new CacheControl();
cache.setNoCache(true);
ResponseBuilderImpl builder = new ResponseBuilderImpl();
builder.cacheControl(cache);
Response r = builder.build();

5. Returning entities with generic type information

如果应用程序需要更多的控制返回对象的MIME Type或者Entity Provider序列化Reponse, JAX-RS类

javax.ws.rs.core.GenericEntity<T>提供了更细粒度的控制。

Creating a GenericEntity<T> object

有两种方法：

A. 使用将被包装的Entity来创建GenericEntity<T>的子类：

import javax.ws.rs.core.GenericEntity;

List<String> list = new ArrayList<String>();

GenericEntity<List<String>> entity = new GenericEntity<List<String>>(list) {};
Response response = Response.ok(entity).build();

B. 使用Entity的Generic Type信息直接创建Instance:

import javax.ws.rs.core.GenericEntity;

AtomicInteger result = new AtomicInteger(12);

GenericEntity<AtomicInteger> entity = new GenericEntity<AtomicInteger>(result,
result.getClass().getGenericSuperclass());
Response response = Response.ok(entity).build();

返回信息给Consumer

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