Spring rest对etag支持

原文地址：http://www.javaarch.net/jiagoushi/698.htm

 

Spring rest对etag支持

etag（entity tag)是http响应头中用来判断对应响应结果是否修改。可以使用hash算法来计算etag的值。

比如：第一次访问

	curl -H "Accept: application/json" -i http://localhost:8080/rest-sec/api/resources/1
	
响应为：

	HTTP/1.1 200 OK
	ETag: "f88dd058fe004909615a64f01be66a7"
	Content-Type: application/json;charset=UTF-8
	Content-Length: 52

那么下次客户端访问的时候If-None-Match或者If-Match头来让服务端判断是否修改


	curl -H "Accept: application/json" -H 'If-None-Match: "f88dd058fe004909615a64f01be66a7"'
	 -i http://localhost:8080/rest-sec/api/resources/1
	
如果没有修改，则服务端会返回

	HTTP/1.1 304 Not Modified
	ETag: "f88dd058fe004909615a64f01be66a7"
	
我们重新修改请求参数：

	curl --user [email protected]:adminpass -H "Content-Type: application/json" -i 
	  -X PUT --data '{ "id":1, "name":"newRoleName2", "description":"theNewDescription" }' http://localhost:8080/rest-sec/api/resources/1
	  
响应为：

	HTTP/1.1 200 OK
	ETag: "d41d8cd98f00b204e9800998ecf8427e"
	Content-Length: 0
	
如果我们再访问
	
	curl -H "Accept: application/json" -H 'If-None-Match: "f88dd058fe004909615a64f01be66a7"' -i 
	http://localhost:8080/rest-sec/api/resources/1
	
则返回：

	HTTP/1.1 200 OK
	ETag: "03cb37ca667706c68c0aad4cb04c3a211"
	Content-Type: application/json;charset=UTF-8
	Content-Length: 56
	
spring对etag的支持，在web.xml中加上这个filter

	<filter>
	   <filter-name>etagFilter</filter-name>
	   <filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class>
	</filter>
	<filter-mapping>
	   <filter-name>etagFilter</filter-name>
	   <url-pattern>/api/*</url-pattern>
	</filter-mapping>
	
测试etags

第一次判断etag不为空

	@Test
	public void givenResourceExists_whenRetrievingResource_thenEtagIsAlsoReturned() {
		// Given
		Resource existingResource = getApi().create(new Resource());
		String uriOfResource = baseUri + "/" + existingResource.getId();
	 
		// When
		Response findOneResponse = RestAssured.given().
		  header("Accept", "application/json").get(uriOfResource);
	 
		// Then
		assertNotNull(findOneResponse.getHeader(HttpHeaders.ETAG));
	}
	
第二次，我们从上一次取出etag之后把etag发送给服务端验证

	@Test
	public void givenResourceWasRetrieved_whenRetrievingAgainWithEtag_thenNotModifiedReturned() {
		// Given
		T existingResource = getApi().create(createNewEntity());
		String uriOfResource = baseUri + "/" + existingResource.getId();
		Response findOneResponse = RestAssured.given().
		  header("Accept", "application/json").get(uriOfResource);
		String etagValue = findOneResponse.getHeader(HttpHeaders.ETAG);
	 
		// When
		Response secondFindOneResponse= RestAssured.given().
		  header("Accept", "application/json").headers("If-None-Match", etagValue)
		  .get(uriOfResource);
	 
		// Then
		assertTrue(secondFindOneResponse.getStatusCode() == 304);
	}

测试服务端响应结果变化了，则

	@Test
	public void givenResourceWasRetrieved_whenRetrievingAgainWithEtag_thenNotModifiedReturned() {
		// Given
		T existingResource = getApi().create(createNewEntity());
		String uriOfResource = baseUri + "/" + existingResource.getId();
		Response findOneResponse = RestAssured.given().
		  header("Accept", "application/json").get(uriOfResource);
		String etagValue = findOneResponse.getHeader(HttpHeaders.ETAG);
	 
		existingResource.setName(randomAlphabetic(6))
		getApi().update(existingResource.setName(randomString));
	 
		// When
		Response secondFindOneResponse= RestAssured.given().
		  header("Accept", "application/json").headers("If-None-Match", etagValue)
		  .get(uriOfResource);
	 
		// Then
		assertTrue(secondFindOneResponse.getStatusCode() == 200);
	}
	
如果请求带上不正确的etag值并且加上if-match判断，则会返回412Precondition Failed

	@Test
	public void givenResourceExists_whenRetrievedWithIfMatchIncorrectEtag_then412IsReceived() {
		// Given
		T existingResource = getApi().create(createNewEntity());
	 
		// When
		String uriOfResource = baseUri + "/" + existingResource.getId();
		Response findOneResponse = RestAssured.given().header("Accept", "application/json").
		  headers("If-Match", randomAlphabetic(8)).get(uriOfResource);
	 
		// Then
		assertTrue(findOneResponse.getStatusCode() == 412);
	}
	
github示例地址：https://github.com/eugenp/REST