Spring REST实践之客户端和测试

RestTemplate

可参考spring实战来写这部分。

RestTemplate免于编写乏味的样板代码，RestTemplate定义了33个与REST资源交互的方法，涵盖了HTTP动作的各种形式，其实这些方法只有11个独立的方法，而每一个方法都由3个重载的变种。

delete()：在特定的URL上对资源执行HTTP DELETE操作
exchange()：在URL上执行特定的HTTP方法，返回包含对象的ResponseEntity，这个对象是从响应体中映射得到的
execute()：在URL上执行特定的HTTP方法，返回一个从响应体映射得到的对象
getForEntity()：发送一个HTTP GET请求，返回的ResponseEntity包含了响应体所映射成的对象
getForObject()：GET资源，返回的请求体将映射为一个对象
headForHeaders()：发送HTTP HEAD请求，返回包含特定资源URL的HTTP头
optionsForAllow()：发送HTTP OPTIONS请求，返回对特定URL的Allow头信息
postForEntity()：POST数据，返回包含一个对象的ResponseEntity，这个对象是从响应体中映射得到
postForLocation()：POST数据，返回新资源的URL
postForObject()：POST数据，返回的请求体将匹配为一个对象
put()：PUT资源到特定的URL

除了TRACE，RestTemplate涵盖了所有的HTTP动作。除此之外，execute()和exchange()提供了较低层次的通用方法来使用任意的HTTP方法。

每个方法都以3种方法进行了重载：

一个使用java.net.URI作为URL格式，不支持参数化URL
一个使用String作为URL格式，并使用Map指明URL参数
一个使用String作为URL格式，并使用可变参数列表指明URL参数

GET资源

有两种执行GET请求的方法：getForObject()和getForEntity()。3个getObject()方法的签名如下：

T getForObject(URI url, Class responseType) throws RestClientException;
T getForObject(String url, Class responseType, Object... uriVariables) throws RestClientException;
T getForObject(String url, Class responseType, Map<String, ?> uriVariables) throws RestClientException;

类似地，getForEntity()方法的签名如下：

ResponseEntity getForObject(URI url, Class responseType) throws RestClientException;
ResponseEntity getForObject(String url, Class responseType, Object... uriVariables) throws RestClientException;
ResponseEntity getForObject(String url, Class responseType, Map<String, ?> uriVariables) throws RestClientException;

除了返回类型，getForObject()方法就是getForEntity()方法的镜像。实际上，它们的工作方式大同小异。它们都执行根据URL检索资源的GET请求。它们都将资源根据responseType参数匹配为一定的类型。唯一的区别在于getForObject()只返回所请求类型的对象，而getForEntity()方法会返回请求的对象以及响应的额外信息。

public Spittle[] retrieveSpittlesForSpitter(String username) {
return new RestTemplate().getForObject("http://localhost:8080/Spitter/{spitter}/spittles",
Spittle[].class, username);
}

public Spittle[] retrieveSpittlesForSpitter(String username) {
ResponseEntity<Spittle[]> reponse = new RestTemplate().getForEntity(
"http://localhost:8080/Spitter/{spitter}/spittles",
Spittle[].class, username);

if(reponse.getStatusCode() == HttpStatus.NOT_MODIFIED) {
throw new NotModifiedException();
}

return reponse.getBody();
}

PUT资源

void put(URI url, Object request) throws RestClientException;
void put(String url, Object request, Object... uriVairables) throws RestClientException;
void put(String url, Object request, Map<String, ?> uriVariables) throws RestClientException;

public void updateSpittle(Spittle spittle) throws SpitterException {
try {
String url = "http://localhost:8080/Spitter/spittles/" + spittle.getId();
new RestTemplate().put(new URI(url), spittle);
} catch(URISyntaxException e) {
throw new SpitterUpdateException("Unable to update Spittle", e);
}
}

public void updateSpittle(Spittle spittle) throws SpitterException {
restTemplate.put("http://localhost:8080/Spitter/spittles/{id}",
spittle, spittle.getId());
}

public void updateSpittle(Spittle spittle) throws SpitterException {
Map<String, String> params = new HashMap<String, String>();
params.put("id", spittle.getId());
restTemplate.put("http://localhost:8080/Spitter/spittles/{id}",
spittle, params);
}

DELETE资源

void delete(String url, Object... uriVariables) throws RestClientException;
void delete(String url, Map<String, ?> uriVariables) throws RestClientException;
void delete(URI url) throws RestClientException;

public void deleteSpittle(long id) {
try {
restTemplate.delete(new URI("http://localhost:8080/Spitter/spittles/" + id));
} catch(URISyntaxException e) {

}
}

POST资源数据

POST请求有postForObject()和postForEntity()两种方法，和GET请求的getForObject()和getForEntity()方法类似。getForLocation()是POST请求所特有的。

T postForObject(URI url, Object request, Class responseType) throws RestClientException;
T postForObject(String url, Object request, Class responseType, Object... uriVariables) throws RestClientException;
T postForObject(String url, Object request, Class responseType, Map<String, ?> uriVariables) throws RestClientException;

上面三个方法中，第一个参数都是资源要POST到的URL，第二个参数是要发送的对象，而第三个参数是预期返回的Java类型。在URL作为String类型的两个版本中，第四个参数指定了URL变量（要么是可变参数列表，要么是一个Map）。

T postForObject(URI url, Object request, Class responseType) throws RestClientException;
T postForObject(String url, Object request, Class responseType, Object... uriVariables) throws RestClientException;
T postForObject(String url, Object request, Class responseType, Map<String, ?> uriVariables) throws RestClientException;

ResponseEntity response = new RestTemplate().postForEntity("http://localhost:8080/Spitter/spitters",
spitter, Spitter.class);
Spitter spitter = response.getBody();
URI url = response.getHeaders().getLocation();

postForLacation()会在POST请求的请求体中发送一个资源到服务器端，返回的不再是资源对象，而是创建资源的位置。

URI postForLocation(String url, Object request, Object... uriVariables) throws RestClientException;
URI postForLocation(String url, Object request, Map<String, ?> uriVariables) throws RestClientException;
URI postForLocation(URI url, Object request) throws RestClientException;

public String postSpitter(Spitter spitter) {
RestTemplate rest = new RestTemplate();
return rest.postForLocation("http://localhost:8080/Spitter/spitters",
spitter).toString();
}

交换资源

exchange方法可以在发送个服务器端的请求中设置头信息。

ResponseEntity exchange(URI url, HttpMethod method, HttpEntity<?> requestEntity, Class responseType) throws RestClientException;

ResponseEntity exchange(String url, HttpMethod method, HttpEntity<?> requestEntity, Class responseType, Object... uriVariables) throws RestClientException;

ResponseEntity exchange(String url, HttpMethod method, HttpEntity requestEntity, Class responseType, Map uriVariables) throws RestClientException;

MultiValueMap<String, String> headers = new LinkedMultiValueMap<String, String>();
headers.add("Accept", "application/json");
HttpEntity