restTemplate学习

什么是RestTemplate

RestTemplate用于同步client端的核心类，简化了与http服务的通信，并满足RestFul原则，程序代码可以给它提供URL，并提取结果
默认情况下，RestTemplate默认使用jdk提供http链接的能力（HttpURLConnection）
可以通过setRequestFactory属性切换到不同的HTTP源，Apache HttpComponents,Netty和OkHttp。

常用方法

restTemplate其他的先不讲，直接上来操作，熟个手

getForObject

getForObject函数实际上是对getForEntity函数的进一步封装，如果你只关注返回的消息体的内容，对其他信息都不关注，此时可以使用getForObject

public T getForObject(String url, Class responseType, Object… uriVariables)

String oneGet = restTemplate.getForObject("http://localhost:6788/oneGet", String.class);
System.out.println(oneGet);
//可以用一个数字做占位符，最后是一个可变长度的参数，来一一替换前面的占位符
String oneGet1 = restTemplate.getForObject("http://localhost:6788/oneGet/{1}", String.class,"1");
System.out.println(oneGet1);

public T getForObject(String url, Class responseType, Map<String, ?> uriVariables)

//也可以前面使用id={id}这种形式，最后一个参数是一个map，map的key即为前边占位符的名字，map的value为参数值
HashMap<String, Object> twoGetMap = new HashMap<>();
twoGetMap.put("id","1");
String twoGet = restTemplate.getForObject("http://localhost:6788/twoGet?id={id}", String.class,twoGetMap);
System.out.println(twoGet);

public T getForObject(URI url, Class responseType)

String threeGet = restTemplate.getForObject(new URI("http://localhost:6788/threeGet"), String.class);
System.out.println(threeGet);

====================getForObject=======================
{"code":1,"message":"","data":"oneGet"}
{"code":1,"message":"","data":"oneGet1--1"}
{"code":1,"message":"","data":"twoGet--1"}
{"code":1,"message":"","data":"threeGet"}

getForEntity

getForEntity方法的返回值是一个ResponseEntity，ResponseEntity是Spring对HTTP请求响应的封装，包括了几个重要的元素，如响应码、contentType、contentLength、响应消息体等

public ResponseEntity getForEntity(String url, Class responseType, Object… uriVariables)

ResponseEntity<String> oneGetEntity = restTemplate.getForEntity("http://localhost:6788/oneGet", String.class);
System.out.println(oneGetEntity);
ResponseEntity<String> oneGetEntity1 = restTemplate.getForEntity("http://localhost:6788/oneGet/{1}", String.class, "1");
System.out.println(oneGetEntity1);

public ResponseEntity getForEntity(String url, Class responseType, Map<String, ?> uriVariables)

//也可以前面使用id={id}这种形式，最后一个参数是一个map，map的key即为前边占位符的名字，map的value为参数值
HashMap<String, Object> twoGetMapEntity = new HashMap<>();
twoGetMapEntity.put("id","1");
ResponseEntity<String> twoGetEntity = restTemplate.getForEntity("http://localhost:6788/twoGet?id={id}", String.class,twoGetMapEntity);
System.out.println(twoGetEntity);

public ResponseEntity getForEntity(URI url, Class responseType)

ResponseEntity<String> threeGetEntity = restTemplate.getForEntity(new URI("http://localhost:6788/threeGet"), String.class);
System.out.println(threeGetEntity);

====================getForEntity=======================
<200,{"code":1,"message":"","data":"oneGet"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>
<200,{"code":1,"message":"","data":"oneGet1--1"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>
<200,{"code":1,"message":"","data":"twoGet--1"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>
<200,{"code":1,"message":"","data":"threeGet"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>

headForHeaders

获取请求头，用于检查对象是否存在，不返回body信息

public HttpHeaders headForHeaders(String url, Object… uriVariables)

HttpHeaders oneHeaders = restTemplate.headForHeaders("http://localhost:6788/oneGet");
System.out.println(oneHeaders);

public HttpHeaders headForHeaders(String url, Map<String, ?> uriVariables)

HashMap<String, Object> headMap = new HashMap<>();
headMap.put("id","1");
HttpHeaders twoHeaders = restTemplate.headForHeaders("http://localhost:6788/twoGet?id={id}", headMap);
System.out.println(twoHeaders);

public HttpHeaders headForHeaders(URI url)

HttpHeaders threeHeaders = restTemplate.headForHeaders(new URI("http://localhost:6788/oneGet"));
System.out.println(threeHeaders);

====================headForHeaders=======================
[Content-Type:"application/json;charset=UTF-8", Content-Length:"39", Date:"Fri, 24 May 2019 02:05:03 GMT"]
[Content-Type:"application/json;charset=UTF-8", Content-Length:"42", Date:"Fri, 24 May 2019 02:05:03 GMT"]
[Content-Type:"application/json;charset=UTF-8", Content-Length:"39", Date:"Fri, 24 May 2019 02:05:03 GMT"]

postForLocation

post提交，获取重定向的url,该Uri表示新资源的位置

public URI postForLocation(String url, @Nullable Object request, Object… uriVariables)

HttpEntity<Object> entity = new HttpEntity<>(null,null);//第一个参数为body参数，第二个参数为headers（请求头）
URI oneUri = restTemplate.postForLocation("http://localhost:6788/onePost",entity);
System.out.println(oneUri);
URI oneUri1 = restTemplate.postForLocation("http://localhost:6788/onePost?id={id}",entity,"---1");
System.out.println(oneUri1);

public URI postForLocation(String url, @Nullable Object request, Map<String, ?> uriVariables)

HttpEntity<Object> entity = new HttpEntity<>(null,null);
HashMap<String, Object> uriMap = new HashMap<>();
uriMap.put("id","---1");
URI twoUri = restTemplate.postForLocation("http://localhost:6788/onePost?id={id}", entity, uriMap);
System.out.println(twoUri);

public URI postForLocation(URI url, @Nullable Object request)

URI threeUri = restTemplate.postForLocation(new URI("http://localhost:6788/onePost"), entity);
System.out.println(threeUri);

====================postForLocation=======================
https://blog.csdn.net/YCJ_xiyang/column/info/38209
https://blog.csdn.net/YCJ_xiyang/column/info/38209---1
https://blog.csdn.net/YCJ_xiyang/column/info/38209---1
https://blog.csdn.net/YCJ_xiyang/column/info/38209

postForObject

public T postForObject(String url, @Nullable Object request, Class responseType,
Object… uriVariables)

HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
Gson gson = new Gson();
Map<String,String> postMaps = new HashMap<>();
postMaps.put("name","cat");
HttpEntity<Object> postEntity = new HttpEntity<>(gson.toJson(postMaps),headers);
String onePost = restTemplate.postForObject("http://localhost:6788/onePost",postEntity,String.class);
System.out.println(onePost);
String onePost1 = restTemplate.postForObject("http://localhost:6788/onePost?id={id}",postEntity,String.class,"---1");
System.out.println(onePost1);

public T postForObject(String url, @Nullable Object request, Class responseType,
Map<String, ?> uriVariables)

HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
Gson gson = new Gson();
Map<String,String> postMaps = new HashMap<>();
postMaps.put("name","cat");
HttpEntity<Object> postEntity = new HttpEntity<>(gson.toJson(postMaps),headers);
HashMap<String, Object> postMap = new HashMap<>();
postMap.put("id","---1");
String twoPost = restTemplate.postForObject("http://localhost:6788/onePost?id={id}", postEntity,String.class, postMap);
System.out.println(twoPost);

public T postForObject(URI url, @Nullable Object request, Class responseType)

HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
Gson gson = new Gson();
Map<String,String> postMaps = new HashMap<>();
postMaps.put("name","cat");
HttpEntity<Object> postEntity = new HttpEntity<>(gson.toJson(postMaps),headers);
String threePost = restTemplate.postForObject(new URI("http://localhost:6788/onePost"), postEntity,String.class);
System.out.println(threePost);

====================postForObject=======================
{"code":1,"message":"","data":"onePostnull----{\"name\":\"cat\"}"}
{"code":1,"message":"","data":"onePost---1----{\"name\":\"cat\"}"}
{"code":1,"message":"","data":"onePost---1----{\"name\":\"cat\"}"}
{"code":1,"message":"","data":"onePostnull----{\"name\":\"cat\"}"}

postForEntity

public ResponseEntity postForEntity(String url, @Nullable Object request,
Class responseType, Object… uriVariables)

HttpHeaders postHeadersEntity = new HttpHeaders();
postHeadersEntity.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
MultiValueMap<String,String> body = new LinkedMultiValueMap<>();
body.add("name","tom");
HttpEntity<Object> postEntitys = new HttpEntity<>(body,postHeadersEntity);
ResponseEntity<String> onePostEntity = restTemplate.postForEntity("http://localhost:6788/onePostEntity", postEntitys, String.class);
System.out.println(onePostEntity);
ResponseEntity<String> onePostEntity1 = restTemplate.postForEntity("http://localhost:6788/onePostEntity?id={id}",postEntitys,String.class,"---1");
System.out.println(onePostEntity1);

public ResponseEntity postForEntity(String url, @Nullable Object request,
Class responseType, Map<String, ?> uriVariables)

HttpHeaders postHeadersEntity = new HttpHeaders();
postHeadersEntity.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
MultiValueMap<String,String> body = new LinkedMultiValueMap<>();
body.add("name","tom");
HttpEntity<Object> postEntitys = new HttpEntity<>(body,postHeadersEntity);
HashMap<String, Object> postMapEntity = new HashMap<>();
postMapEntity.put("id","---1");
ResponseEntity<String> twoPostEntity = restTemplate.postForEntity("http://localhost:6788/onePostEntity?id={id}", postEntitys,String.class, postMapEntity);
System.out.println(twoPostEntity);

public ResponseEntity postForEntity(URI url, @Nullable Object request, Class responseType)

HttpHeaders postHeadersEntity = new HttpHeaders();
postHeadersEntity.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
MultiValueMap<String,String> body = new LinkedMultiValueMap<>();
body.add("name","tom");
HttpEntity<Object> postEntitys = new HttpEntity<>(body,postHeadersEntity);
HashMap<String, Object> postMapEntity = new HashMap<>();
postMapEntity.put("id","---1");
ResponseEntity<String> threePostEntity = restTemplate.postForEntity(new URI("http://localhost:6788/onePostEntity"), postEntitys,String.class);
System.out.println(threePostEntity);

扩展content-type:form-data

 HttpHeaders postHeadersEntitys = new HttpHeaders();
 postHeadersEntity.add("Content-Type", MediaType.MULTIPART_FORM_DATA_VALUE);
 MultiValueMap<String,String> bodys = new LinkedMultiValueMap<>();
 bodys.add("name","sam");
 HttpEntity<Object> postEntityss = new HttpEntity<>(bodys,postHeadersEntitys);
 ResponseEntity<String> onePostEntitys = restTemplate.postForEntity("http://localhost:6788/onePostEntity", postEntityss, String.class);
 System.out.println(onePostEntitys);

====================postForEntity=======================
<200,{"code":1,"message":"","data":"onePostEntitynull----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
<200,{"code":1,"message":"","data":"onePostEntity---1----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
<200,{"code":1,"message":"","data":"onePostEntity---1----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
<200,{"code":1,"message":"","data":"onePostEntitynull----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
====================postForEntity扩展=======================
<200,{"code":1,"message":"","data":"onePostEntitynull----sam"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>

put

put 在restful中表示更新或创建，清楚参数和post差不多，只不过没有返回值，这里只演示一种

public void put(String url, @Nullable Object request, Object… uriVariables)

HttpHeaders putHeaders = new HttpHeaders();
putHeaders.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
HttpEntity<Object> putEntity = new HttpEntity<>(null,putHeaders);
restTemplate.put("http://localhost:6788/put?id={id}",putEntity,"--1");

public void put(String url, @Nullable Object request, Map<String, ?> uriVariables)
public void put(URI url, @Nullable Object request)

patchForObject

patch接口表示修改,参数和上面的类似，不一一演示了
注意：restTemplate默认使用的jdk的HttpURLConnection，不支持patch，需要替换为Apache HttpComponents
引入依赖compile group: 'org.apache.httpcomponents', name: 'httpclient', version: '4.5.2'
restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory());

public T patchForObject(String url, @Nullable Object request, Class responseType,
Object… uriVariables)

HttpHeaders patchHeaders = new HttpHeaders();
patchHeaders.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
HttpEntity<Object> patchEntity = new HttpEntity<>(null,patchHeaders);
String patch = restTemplate.patchForObject("http://localhost:6788/patch?id={id}", patchEntity, String.class, "--1");
System.out.println(patch);

public T patchForObject(String url, @Nullable Object request, Class responseType,
Map<String, ?> uriVariables)

public T patchForObject(URI url, @Nullable Object request, Class responseType)

====================patchForObject=======================
{"code":1,"message":"","data":"patch----1"}

delete

顾名思义：表示删除的接口,无返回值

public void delete(String url, Object… uriVariables)

restTemplate.delete("http://localhost:6788/delete?id={id}",  "--1");

public void delete(String url, Map<String, ?> uriVariables)

public void delete(URI url)

====================delete=======================
[GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS]

optionsForAllow

询问可以执行哪些方法，参数跟上面类似，演示一种

public Set optionsForAllow(String url, Object… uriVariables)

 Set<HttpMethod> httpMethods = restTemplate.optionsForAllow("http://localhost:6788/optionsForAllow?id={id}", "--1");
 System.out.println(httpMethods);

public Set optionsForAllow(String url, Map<String, ?> uriVariables)

public Set optionsForAllow(URI url)

====================optionsForAllow=======================
[GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS]

exchange

exchange方法提供统一的方法模板进行四种请求：POST,PUT,DELETE,GET
说明：
1）url: 请求地址；
2）method: 请求类型(如：POST,PUT,DELETE,GET)；
3）requestEntity: 请求实体，封装请求头，请求内容
4）responseType: 响应类型，根据服务接口的返回类型决定
5）uriVariables: url中参数变量值

public ResponseEntity exchange(String url, HttpMethod method,@Nullable HttpEntity<?> requestEntity,
Class responseType, Object… uriVariables)
public ResponseEntity exchange(String url, HttpMethod method,@Nullable HttpEntity<?> requestEntity,
Class responseType ,Map<String, ?> uriVariables )
public ResponseEntity exchange(URI url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,
Class responseType)

前面3种，参数类似，和上面的操作相同

public ResponseEntity exchange(String url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,
ParameterizedTypeReference responseType, Object… uriVariables)
public ResponseEntity exchange(String url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,
ParameterizedTypeReference responseType, Map<String, ?> uriVariables)
public ResponseEntity exchange(URI url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,
ParameterizedTypeReference responseType)
public ResponseEntity exchange(RequestEntity<?> requestEntity, ParameterizedTypeReference responseType)

上面4种，ParameterizedTypeReference 支持即泛型类作为返回类型
例子：ParameterizedTypeReference 例子

public ResponseEntity exchange(RequestEntity<?> requestEntity, Class responseType)

最后一种RequestEntity<?>里面加请求头，请求方法，请求地址

//get添加请求头
HttpHeaders exchangeHeaders = new HttpHeaders();
exchangeHeaders.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
URI url = new URI("http://localhost:6788/exchange?id=--1");
RequestEntity<Object> orderEntity = new RequestEntity<>(exchangeHeaders,HttpMethod.GET,url);
ResponseEntity<String> result = restTemplate.exchange(orderEntity, String.class);
System.out.println(result);
====================exchange=======================
<200,{"code":1,"message":"","data":"exchange--1"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 02:45:26 GMT"]>

spring学习之restTemplate常用方法介绍

restTemplate学习

什么是RestTemplate

常用方法

getForObject

getForEntity

headForHeaders

postForLocation

postForObject

postForEntity

put

patchForObject

delete

optionsForAllow

exchange

例子源码地址

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