1.概要
RestTemplate是Spring提供的用於訪問的Rest服務的客戶端，提供用於訪問Rest服務的客戶端，RestTemplate提供了多種便捷訪問遠程Http服務的方法，能夠大大提高客戶端的編寫效率。
2.應用
常規配置
public MyRestClientService(RestTemplateBuilder restTemplateBuilder) {
this.restTemplate = restTemplateBuilder
.basicAuthorization("username", "password")
.setConnectTimeout(3000)
.setReadTimeout(5000)
.rootUri("http://api.example.com/")
.build();
} |
ClientHttpRequestInterceptor
學習使用帶有Spring RestTemplate的ClientHttpRequestInterceptor，以Spring AOP風格記錄請求和響應頭和主體。
攔截器記錄請求和響應
import org.slf4j.Logger;import org.slf4j.LoggerFactory;
import org.springframework.http.HttpRequest;
import org.springframework.http.client.ClientHttpRequestExecution;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.util.StreamUtils;
import java.io.IOException;
import java.nio.charset.Charset;
public class RequestResponseLoggingInterceptor implements ClientHttpRequestInterceptor {
private final Logger log = LoggerFactory.getLogger(this.getClass());
@Override
public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException
{
logRequest(request, body);
ClientHttpResponse response = execution.execute(request, body);
logResponse(response);
//Add optional additional headers
response.getHeaders().add("headerName", "VALUE");
return response;
}
private void logRequest(HttpRequest request, byte[] body) throws IOException
{
if (log.isDebugEnabled())
{
log.debug("===========================request begin================================================");
log.debug("URI : {}", request.getURI());
log.debug("Method : {}", request.getMethod());
log.debug("Headers : {}", request.getHeaders());
log.debug("Request body: {}", new String(body, "UTF-8"));
log.debug("==========================request end================================================");
}
}
private void logResponse(ClientHttpResponse response) throws IOException
{
if (log.isDebugEnabled())
{
log.debug("============================response begin==========================================");
log.debug("Status code : {}", response.getStatusCode());
log.debug("Status text : {}", response.getStatusText());
log.debug("Headers : {}", response.getHeaders());
log.debug("Response body: {}", StreamUtils.copyToString(response.getBody(), Charset.defaultCharset()));
log.debug("=======================response end=================================================");
}
}
} |
注冊ClientHttpRequestInterceptor
@Bean
public RestTemplate restTemplate(){
RestTemplate restTemplate = new RestTemplate();
restTemplate.setRequestFactory(newBufferingClientHttpRequestFactory(clientHttpRequestFactory()));
restTemplate.setMessageConverters(Collections.singletonList(mappingJacksonHttpMessageConverter()));
restTemplate.setInterceptors( Collections.singletonList(newRequestResponseLoggingInterceptor()) );
return restTemplate;
} |
三、請求示例
GET
private static void getEmployees(){
final String uri = "http://localhost:8080/springrestexample/employees";
RestTemplate restTemplate = new RestTemplate();
String result = restTemplate.getForObject(uri, String.class);
System.out.println(result);
} |
使用RestTemplate定制HTTP頭文件
private static void getEmployees(){
final String uri = "http://localhost:8080/springrestexample/employees";
RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
HttpEntity<String> entity = new HttpEntity<String>("parameters", headers);
ResponseEntity<String> result = restTemplate.exchange(uri, HttpMethod.GET, entity, String.class);
System.out.println(result);
} |
Get請求獲取響應為一個對象
private static void getEmployees(){
final String uri = "http://localhost:8080/springrestexample/employees";
RestTemplate restTemplate = new RestTemplate();
EmployeeListVO result = restTemplate.getForObject(uri, EmployeeListVO.class);
System.out.println(result);
} |
URL 參數
private static void getEmployeeById(){
final String uri = "http://localhost:8080/springrestexample/employees/{id}";
Map<String, String> params = new HashMap<String, String>();
params.put("id", "1");
RestTemplate restTemplate = new RestTemplate();
EmployeeVO result = restTemplate.getForObject(uri, EmployeeVO.class, params);
System.out.println(result);
} |
POST
private static void createEmployee(){
final String uri = "http://localhost:8080/springrestexample/employees";
EmployeeVO newEmployee = new EmployeeVO(-1, "Adam", "Gilly", "test@email.com");
RestTemplate restTemplate = new RestTemplate();
EmployeeVO result = restTemplate.postForObject( uri, newEmployee, EmployeeVO.class);
System.out.println(result);
} |
Submit Form Data
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
MultiValueMap<String, String> map= new LinkedMultiValueMap<>();
map.add("id", "1");
HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);
RestTemplate restTemplate = new RestTemplate();
EmployeeVO result = restTemplate.postForObject( uri, request, EmployeeVO.class);
System.out.println(result); |
PUT
private static void updateEmployee(){
final String uri = "http://localhost:8080/springrestexample/employees/{id}";
Map<String, String> params = new HashMap<String, String>();
params.put("id", "2");
EmployeeVO updatedEmployee = new EmployeeVO(2, "New Name", "Gilly", "test@email.com");
RestTemplate restTemplate = new RestTemplate();
restTemplate.put ( uri, updatedEmployee, params);
} |
Simple PUT
Foo updatedInstance = new Foo("newName");
updatedInstance.setId(createResponse.getBody().getId());
String resourceUrl =
fooResourceUrl + '/' + createResponse.getBody().getId();
HttpEntity<Foo> requestUpdate = new HttpEntity<>(updatedInstance, headers);
template.exchange(resourceUrl, HttpMethod.PUT, requestUpdate, Void.class); |
使用.exchange和請求回調
RequestCallback requestCallback(final Foo updatedInstance) {
return clientHttpRequest -> {
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(clientHttpRequest.getBody(), updatedInstance);
clientHttpRequest.getHeaders().add(
HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
clientHttpRequest.getHeaders().add(
HttpHeaders.AUTHORIZATION, "Basic " + getBase64EncodedLogPass());
};
} |
DELETE
private static void deleteEmployee(){
final String uri = "http://localhost:8080/springrestexample/employees/{id}";
Map<String, String> params = new HashMap<String, String>();
params.put("id", "2");
RestTemplate restTemplate = new RestTemplate();
restTemplate.delete ( uri, params );
}
3.簡述
RestTemplate是Spring用於同步client端的核心類，簡化了與hhtp服務通信，並滿足RestFul原則，程序代碼可以給它提供URL，並提取結果。默認情況下。RestTemplate默認以來jdk的http連接工具。也可以通過setRequestFactory屬性切換到不同的HTTP源，比如Apache，HttpComponents、Netty和OkHttp。
3.1 該類的入口主要根據HTTP六個方法制定：
| Http method | RestTemplate methods |
| DELETE | delete |
| GET | getForObject |
| getFOrEntity | |
| HEAD | headForHeaders |
| OPTIONS | optionsForAllow |
| POST | postForLoation |
| postForObject | |
| PUT | put |
| any | exchange |
| execute |
在內部，
RestTemplate默認使用
HttpMessageConverter實例將
HTTP消息轉換成
POJO或者從
POJO轉換成
HTTP消息。默認情況下會注冊主mime類型的轉換器，但也可以通過
setMessageConverters注冊其他的轉換器。(其實這點在使用的時候是察覺不到的，很多方法有一個responseType 參數，它讓你傳入一個響應體所映射成的對象，然后底層用HttpMessageConverter將其做映射)
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
HttpMessageConverter.java源碼：
public interface HttpMessageConverter<T> { //指示此轉換器是否可以讀取給定的類。 boolean canRead(Class<?> clazz, @Nullable MediaType mediaType); //指示此轉換器是否可以寫給定的類。 boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType); //返回List<MediaType> List<MediaType> getSupportedMediaTypes(); //讀取一個inputMessage T read(Class<? extends T> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException; //往output message寫一個Object void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException; }
在內部，
RestTemplate默認使用
SimpleClientHttpRequestFactory和
DefaultResponseErrorHandler來分別處理
HTTP的創建和錯誤，但也可以通過
setRequestFactory和
setErrorHandler來覆蓋。
4.get請求實踐
4.1 getForObject()方法
public <T> T getForObject(String url, Class<T> responseType, Object... uriVariables){} public <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables) public <T> T getForObject(URI url, Class<T> responseType)
getForObject()其實比
getForEntity()多包含了將HTTP轉成POJO的功能，但是
getForObject沒有處理
response的能力。因為它拿到手的就是成型的
pojo。省略了很多
response的信息。
4.1.1 pojo
public class Notice { private int status; private Object msg; private List<DataBean> data; } public class DataBean { private int noticeId; private String noticeTitle; private Object noticeImg; private long noticeCreateTime; private long noticeUpdateTime; private String noticeContent; }
4.1.2 不帶get請求
/** * 不帶參的get請求 */ @Test public void restTemplateGetTest(){ RestTemplate restTemplate = new RestTemplate(); Notice notice = restTemplate.getForObject("http://xxx.top/notice/list/1/5" , Notice.class); System.out.println(notice); }
控制台打印：
INFO 19076 --- [ main] c.w.s.c.w.c.HelloControllerTest : Started HelloControllerTest in 5.532 seconds (JVM running for 7.233) Notice{status=200, msg=null, data=[DataBean{noticeId=21, noticeTitle='aaa', noticeImg=null, noticeCreateTime=1525292723000, noticeUpdateTime=1525292723000, noticeContent='<p>aaa</p>'}, DataBean{noticeId=20, noticeTitle='ahaha', noticeImg=null, noticeCreateTime=1525291492000, noticeUpdateTime=1525291492000, noticeContent='<p>ah.......'
示例：4.1.3 帶參數的get請求1
Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/{1}/{2}"
, Notice.class,1,5);
明眼人一眼能看出是用了占位符{1}。
示例：4.1.4 帶參數的get請求2
Map<String,String> map = new HashMap(); map.put("start","1"); map.put("page","5"); Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/" , Notice.class,map);
明眼人一看就是利用map裝載參數，不過它默認解析的是PathVariable的url形式。
4.2 getForEntity()方法
public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables){} public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables){} public <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType){}
與getForObject()方法不同的是返回的是
ResponseEntity對象，如果需要轉換成pojo，還需要json工具類的引入，這個按個人喜好用。不會解析json的可以百度
FastJson或者
Jackson等工具類。然后我們就研究一下
ResponseEntity下面有啥方法。
ResponseEntity、HttpStatus、BodyBuilder結構
ResponseEntity.java
public HttpStatus getStatusCode(){} public int getStatusCodeValue(){} public boolean equals(@Nullable Object other) {} public String toString() {} public static BodyBuilder status(HttpStatus status) {} public static BodyBuilder ok() {} public static <T> ResponseEntity<T> ok(T body) {} public static BodyBuilder created(URI location) {} ...
HttpStatus.java
public enum HttpStatus { public boolean is1xxInformational() {} public boolean is2xxSuccessful() {} public boolean is3xxRedirection() {} public boolean is4xxClientError() {} public boolean is5xxServerError() {} public boolean isError() {} }
BodyBuilder.java
public interface BodyBuilder extends HeadersBuilder<BodyBuilder> { //設置正文的長度，以字節為單位，由Content-Length標頭 BodyBuilder contentLength(long contentLength); //設置body的MediaType 類型 BodyBuilder contentType(MediaType contentType); //設置響應實體的主體並返回它。 <T> ResponseEntity<T> body(@Nullable T body); ｝
可以看出來，ResponseEntity包含了HttpStatus和BodyBuilder的這些信息，這更方便我們處理response原生的東西。