Spring Cloud系列（七） RestTemplate详解（Finchley.RC2版本）
GET请求
在RestTemplate中对GET请求可以通过如下两种方式实现。
第一种，getForEntity方法。该方法返回的是ResponseEntity，该对象是Spring对Http请求响应的封装。其中主要存储了HTTP的几个重要元素，比如HTTP请求状态码的枚举对象HttpStatus（我们常说的404,500）、在他的父类HttpEntity中还存储着HTTP请求的头信息对象HttpHeaders以及泛型类型的请求体对象(响应码、contentType、contentLength、响应消息体等)。
返回字符串类型的对象
ResponseEntity responseEntity = restTemplate.getForEntity("http://HELLO-SERVICE/ribbon/user1?name={1}", String.class,"rest1");
String body = responseEntity.getBody(); 返回自定义类的对象
//返回对象格式
ResponseEntity responseEntity = restTemplate.getForEntity("http://HELLO-SERVICE/ribbon/user2?name={1}&age={2}", User.class,"rest2",22);
User user = responseEntity.getBody(); getForEntity方法提供了三种重载方法
1.getForEntity(String url,Class responseType,Object...urlVariables)
该方法提供了三个参数，第一个参数url为请求的地址，第二个参数responseType是请求响应体body的包装类型，urlVariables为url中的参数绑定。get请求参数可以拼接到url后面，例如：http:ip//xxx/xx?username=xxx，但是更好的方式是使用占位符并配合urlVariables参数实现get请求参数的绑定。注意因为urlVariables是一个数组，所以它的顺序会对应url值占位符的数字顺序。当然你也可以使用json字符串的形式：
ResponseEntity responseEntity = restTemplate.getForEntity("http://HELLO-SERVICE/ribbon/user3?jsonStr={jsonStr}", User.class,"{\"name\":\"rest3\",\"age\":\"22\"}");
User user = responseEntity.getBody(); 2.getForEntity(String url,Class responseType,Map urlVariables)
这里urlVariables参数类型是Map，所以在使用该方法进行参数绑定时必须在占位符中指定Map中参数的key值。
Map params = new HashMap();
params.put("name", "rest4");
params.put("age", 22);
ResponseEntity responseEntity = restTemplate.getForEntity("http://HELLO-SERVICE/ribbon/user2?name={name}&age={age}", User.class,params);
User user = responseEntity.getBody(); 3.getForEntity(URI uri,Class responseType)
该方法使用URI对象来替代之前的url和urlVariables参数来指定访问地址和参数绑定。URI是JDK java.net包下的类，他表示一个统一资源标识符引用。
UriComponents uriComponents = UriComponentsBuilder.fromUriString("http://HELLO-SERVICE/ribbon/user1?name={name}").build().expand("rest5").encode();
URI uri = uriComponents.toUri();
ResponseEntity responseEntity = restTemplate.getForEntity(uri, String.class); 第二种，getForObject方法。该方法可以理解为getForEntity方法的进一步封装。它通过HttpMessageConverterExtractor对HTTP的请求响应体body内容进行对象转换，实现请求直接返回包装好的对象内容,该函数少了一步获取body的步骤所以更方便。比如：
String result = restTemplate.getForObject("http://HELLO-SERVICE/ribbon/user1?name={1}",String.class,"rest6");
//返回对象格式
User user = restTemplate.getForObject("http://HELLO-SERVICE/ribbon/user2?name={1}&age={2}", User.class, "rest7",22);getForObject方法也提供了三种重载方法，参数类似于上面介绍的三个。
- getForObject(String url,Class responseType,Object...urlVariables)
- getForObject(String url,Class responseType,Map urlVariables)
- getForObject(URI uri,Class responseType)
POST请求
在RestTemplate中，对POST请求可以通过如下三个方法进行调用实现。
第一种：postForEntity方法。该方法同GET请求中的getForEntity方法类似，会在调用后返回ResponseEntity
// 参数
User user = new User(1, "rest8", 23);
ResponseEntity responseEntity = restTemplate.postForEntity("http://HELLO-SERVICE/ribbon/user4", user,User.class); postForEntity方法也实现了三种重载方法
- postForEntity(String url,Object request,Class responseType,Object...urlVariables)
- postForEntity(String url,Object request,Class responseType,Map urlVariables)
- postForEntity(URI uri,Object request,Class responseType)
这些函数中的参数方法大部分与getForEntity一致，需要注意的是新加的request参数，该参数可以是一个普通对象，也可以是一个HttpEntity对象。如果是一个普通对象，而非HttpEntity对象的时候，RestTemplate会将请求对象转换为一个HttpEntity对象来处理，其中Object就是request的类型，request内容会被视作完整的body来处理；而如果request是一个HttpEntity对象，那么就会被当作一个完整的HTTP请求对象来处理，这个request中不仅包含了body的内容也包含了header的内容。
HttpHeaders headers = new HttpHeaders();
headers.add("token", "xxxxxxxxxxx");
HttpEntity httpEntity = new HttpEntity(headers);
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
MultiValueMap map= new LinkedMultiValueMap();
map.add("age", "33");
HttpEntity> request = new HttpEntity>(map, headers);
ResponseEntity responseEntity = restTemplate.postForEntity("http://HELLO-SERVICE/ribbon/user5", request, User.class);
第二种，postForObject方法。该方法和getForObject方法类似，它的作用是简化postForEntity的后续处理，通过直接将请求响应的body内容包装成对象来使用。
User user = restTemplate.postForObject("http://HELLO-SERVICE/ribbon/user4", new User(1,"rest10", 22), User.class);postForObject方法也实现了三种重载方法，可以参考get请求的getForObject
- postForObject(String url,Object request,Class responseType,Object...urlVariables)
- postForObject(String url,Object request,Class responseType,Map urlVariables)
- postForObject(URI uri,Object request,Class responseType)
第三种，postForLocation方法。该方法实现了以POST请求提交资源，并返回新资源的URI。
postForLocation方法也实现了三种重载方法，可以参考get请求的getForObject
- postForLocation(String url,Object request,Object...urlVariables)
- postForLocation(String url,Object request,Map urlVariables)
- postForLocation(URI uri,Object request)
由于postForLocation方法会返回新资源的URI，该URI就相当于指定返回类型，所以此方法实现的POST请求不需要像postForEntity和postForObject那样指定responseType。
PUT请求
常规使用
int id = 1;
User user = new User("rest11",22);
restTemplate.put("http://HELLO-SERVICE/ribbon/user6/{1}", user, id);put方法也实现了三种重载方法
- put(String url,Object request,Object...urlVariables)
- put(String url,Object request,Map urlVariables)
- put(URI uri,Object request)
注意：put方法返回类型为void，所以没有返回值。
DELETE请求
int id = 1;
restTemplate.delete("http://HELLO-SERVICE/ribbon/user7/{1}",id);delete方法也实现了三种重载方法
- delete(String url,Object...urlVariables)
- delete(String url,Map urlVariables)
- delete(URI uri)
由于我们进行REST请求时，通常将DELETE请求的唯一标识拼接在url中，所以DELETE请求也不需要request的body信息。
exchange()函数
当然也可以用统一的模板进行GET、POST、PUT、DELETE这四种方式的请求。
restTemplate.exchange(
String url,
HttpMethod method,
HttpEntity requestEntity,
Class responseType,
Object uriVariables[]
)- url: 请求地址；
- method: 请求类型(如：POST,PUT,DELETE,GET)；
- requestEntity: 请求实体，封装请求头，请求内容
- responseType: 响应类型，根据服务接口的返回类型决定
- uriVariables: url中参数变量值
POST请求
String params= "{\"name\":\"小明\",\"age\":33}";
HttpHeaders headers = new HttpHeaders();
MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
headers.setContentType(type);
HttpEntity entity = new HttpEntity(params,headers);
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user9", HttpMethod.POST, entity, User.class); PUT请求
String params= "{\"name\":\"小明\",\"age\":33}";
HttpHeaders headers = new HttpHeaders();
//解决乱码
MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
headers.setContentType(type);
HttpEntity entity = new HttpEntity(params,headers);
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user10", HttpMethod.PUT, entity, String.class); DELETE请求
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user11/{1}", HttpMethod.DELETE, null, String.class,1); GET请求
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user8?jsonStr={jsonStr}",
HttpMethod.GET, null, User.class, "{\"id\":\"2\",\"name\":\"rest13\",\"age\":33}"); 如果返回复杂的数据比如数组或list需要用下面的方式
StringBuilder sb = new StringBuilder();
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/user12?jsonStr={jsonStr}", HttpMethod.GET, null, User[].class,"{\"name\":\"rest17\",\"age\":33}");
for(User user : resp.getBody()){
sb.append(user.toString()+"
");
} StringBuilder sb = new StringBuilder();
ParameterizedTypeReference> res = new ParameterizedTypeReference>(){};
ResponseEntity> resp = restTemplate.exchange("http://HELLO-SERVICE/user13?jsonStr={jsonStr}", HttpMethod.GET, null, res,"{\"name\":\"rest18\",\"age\":33}");
for(User user : resp.getBody()){
sb.append(user.toString()+"
");
} 对于返回属性中有范型数据的复合对象，比如分页对象
ResponseEntity results = restTemplate.exchange(url,HttpMethod.GET, null, String.class, params);
// 借助com.fasterxml.jackson.databind.ObjectMapper 对象来解析嵌套的json字符串
ObjectMapper mapper = new ObjectMapper(); mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
PageInfo page = mapper.readValue(results.getBody(), new TypeReference>() { }); 最后附上代码
消费者代码
import java.net.URI;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;
@RestController
public class RestTemplateController {
@Autowired
private RestTemplate restTemplate;
/**
* getForEntity-返回字符串对象
*
* @return
*/
@GetMapping("rest1")
public String rest1() {
ResponseEntity responseEntity = restTemplate.getForEntity("http://HELLO-SERVICE/ribbon/user1?name={1}",
String.class, "rest1");
String body = responseEntity.getBody();
return body;
}
/**
* getForEntity-返回User对象
*
* @return
*/
@GetMapping("rest2")
public String rest2() {
ResponseEntity responseEntity = restTemplate
.getForEntity("http://HELLO-SERVICE/ribbon/user2?name={1}&age={2}", User.class, "rest2", 22);
User user = responseEntity.getBody();
return user.toString();
}
/**
* getForEntity-以json字符串当作参数
*
* @return
*/
@GetMapping("rest3")
public String rest3() {
ResponseEntity responseEntity = restTemplate.getForEntity(
"http://HELLO-SERVICE/ribbon/user3?jsonStr={jsonStr}", User.class, "{\"name\":\"rest3\",\"age\":22}");
User user = responseEntity.getBody();
return user.toString();
}
/**
* getForEntity-以Map当作参数
*
* @return
*/
@GetMapping("rest4")
public String rest4() {
Map params = new HashMap();
params.put("name", "rest4");
params.put("age", 22);
ResponseEntity responseEntity = restTemplate
.getForEntity("http://HELLO-SERVICE/ribbon/user2?name={name}&age={age}", User.class, params);
User user = responseEntity.getBody();
return user.toString();
}
/**
* getForEntity-URI代替url+urlVariables
*
* @return
*/
@GetMapping("rest5")
public String rest5() {
UriComponents uriComponents = UriComponentsBuilder
.fromUriString("http://HELLO-SERVICE/ribbon/user1?name={name}").build().expand("rest5").encode();
URI uri = uriComponents.toUri();
ResponseEntity responseEntity = restTemplate.getForEntity(uri, String.class);
return responseEntity.getBody();
}
/**
* getForObject 返回字符串
*
* @return
*/
@GetMapping("rest6")
public String rest6() {
String result = restTemplate.getForObject("http://HELLO-SERVICE/ribbon/user1?name={1}", String.class, "rest6");
return result;
}
/**
* getForObject 返回User对象
*
* @return
*/
@GetMapping("rest7")
public String rest7() {
User user = restTemplate.getForObject("http://HELLO-SERVICE/ribbon/user2?name={1}&age={2}", User.class, "rest7",
22);
return user.toString();
}
/**
* postForEntity
*
* @return
*/
@GetMapping("rest8")
public String rest8() {
// 参数
User user = new User(1, "rest8", 23);
ResponseEntity responseEntity = restTemplate.postForEntity("http://HELLO-SERVICE/ribbon/user4", user,
User.class);
return responseEntity.getBody().toString();
}
/**
* postForEntity,HttpEntity传参
*
* @return
*/
@GetMapping("rest9")
public String rest9() {
HttpHeaders headers = new HttpHeaders();
headers.add("token", "xxxxxxxxxxx");
HttpEntity httpEntity = new HttpEntity(headers);
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
MultiValueMap map = new LinkedMultiValueMap();
map.add("age", "33");
HttpEntity> request = new HttpEntity>(map, headers);
ResponseEntity responseEntity = restTemplate.postForEntity("http://HELLO-SERVICE/ribbon/user5", request,
User.class);
return responseEntity.getBody().toString();
}
/**
* postForObject
*
* @return
*/
@GetMapping("rest10")
public String rest10() {
User user = restTemplate.postForObject("http://HELLO-SERVICE/ribbon/user4", new User(1, "rest10", 22),
User.class);
return user.toString();
}
/**
* put请求
*
* @return
*/
@GetMapping("rest11")
public String rest11() {
int id = 1;
User user = new User("rest11", 22);
restTemplate.put("http://HELLO-SERVICE/ribbon/user6/{1}", user, id);
return "success";
}
/**
* delete请求
*
* @return
*/
@GetMapping("rest12")
public String rest12() {
int id = 1;
restTemplate.delete("http://HELLO-SERVICE/ribbon/user7/{1}", id);
return "success";
}
/**
* exchange实现的GET请求
*
* @return
*/
@GetMapping("rest13")
public String rest13() {
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user8?jsonStr={jsonStr}",
HttpMethod.GET, null, User.class, "{\"id\":\"2\",\"name\":\"rest13\",\"age\":33}");
return resp.getBody().toString();
}
/**
* exchange实现的POST请求
*
* @return
*/
@GetMapping("rest14")
public String rest14() {
String params = "{\"name\":\"小明\",\"age\":33}";
HttpHeaders headers = new HttpHeaders();
// 解决参数乱码的问题
MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
headers.setContentType(type);
HttpEntity entity = new HttpEntity(params, headers);
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user9", HttpMethod.POST, entity,
User.class);
return resp.getBody().toString();
}
/**
* exchange实现的PUT请求
*
* @return
*/
@GetMapping("rest15")
public String rest15() {
String params = "{\"name\":\"小明\",\"age\":33}";
HttpHeaders headers = new HttpHeaders();
// 解决参数乱码的问题
MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
headers.setContentType(type);
HttpEntity entity = new HttpEntity(params, headers);
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user10", HttpMethod.PUT,
entity, String.class);
return resp.getBody();
}
/**
* exchange实现的DELETE请求
*
* @return
*/
@GetMapping("rest16")
public String rest16() {
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user11/{1}", HttpMethod.DELETE,
null, String.class, 1);
return resp.getBody();
}
/**
* 返回格式是对象数组
*
* @return
*/
@GetMapping("rest17")
public String rest17() {
StringBuilder sb = new StringBuilder();
ResponseEntity resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user12?jsonStr={jsonStr}",
HttpMethod.GET, null, User[].class, "{\"name\":\"rest17\",\"age\":33}");
for (User user : resp.getBody()) {
sb.append(user.toString() + "
");
}
return sb.toString();
}
/**
* 返回格式是List集合
*
* @return
*/
@GetMapping("rest18")
public String rest18() {
StringBuilder sb = new StringBuilder();
ParameterizedTypeReference> res = new ParameterizedTypeReference>() {
};
ResponseEntity> resp = restTemplate.exchange("http://HELLO-SERVICE/ribbon/user13?jsonStr={jsonStr}",
HttpMethod.GET, null, res, "{\"name\":\"rest18\",\"age\":33}");
for (User user : resp.getBody()) {
sb.append(user.toString() + "
");
}
return sb.toString();
}
}
服务提供者代码
import java.io.BufferedReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.alibaba.fastjson.JSONObject;
import com.wya.springboot.controller.User;
@RestController
@RequestMapping("ribbon")
public class UserController {
@GetMapping("user1")
public String user1(String name) {
return name;
}
@GetMapping("user2")
public User user2(String name, int age) {
return new User(1, name, age);
}
@GetMapping("user3")
public User user3(String jsonStr) {
JSONObject userJson = JSONObject.parseObject(jsonStr);
return new User(1, userJson.getString("name"), userJson.getIntValue("age"));
}
@PostMapping("user4")
public User user4(@RequestBody User user) {
return user;
}
@PostMapping("user5")
public User user5(int age, HttpServletRequest request) {
String token = request.getHeader("token");
return new User(1, token, age);
}
@PutMapping("user6/{id}")
public User user6(@PathVariable("id") int id, @RequestBody User user) {
user.setId(id);
return user;
}
@DeleteMapping("user7/{id}")
public void user7(@PathVariable("id") int id) {
System.out.println(id);
}
@GetMapping("user8")
public User user8(String jsonStr) {
JSONObject user = JSONObject.parseObject(jsonStr);
int id = user.getIntValue("id");
String name = user.getString("name");
int age = user.getIntValue("age");
return new User(id, name, age);
}
@PostMapping("user9")
public User user9(HttpServletRequest request) {
String jsonStr = getBody(request);
JSONObject user = JSONObject.parseObject(jsonStr);
String name = user.getString("name");
int age = user.getIntValue("age");
return new User(1, name, age);
}
@PutMapping("user10")
public User user10(HttpServletRequest request) {
String jsonStr = getBody(request);
JSONObject user = JSONObject.parseObject(jsonStr);
String name = user.getString("name");
int age = user.getIntValue("age");
return new User(1, name, age);
}
@DeleteMapping("user11/{id}")
public String user11(@PathVariable("id") int id) {
System.out.println(id);
return "success";
}
@GetMapping("user12")
public User[] user12(String jsonStr) {
JSONObject user = JSONObject.parseObject(jsonStr);
String name = user.getString("name");
int age = user.getIntValue("age");
User[] users = { new User(1,name, age), new User(2,name, age) };
return users;
}
@GetMapping("user13")
public List user13(String jsonStr) {
JSONObject user = JSONObject.parseObject(jsonStr);
String name = user.getString("name");
int age = user.getIntValue("age");
List users = new ArrayList();
users.add(new User(1,name, age));
users.add(new User(2,name, age));
return users;
}
private String getBody(HttpServletRequest request) {
BufferedReader br = null;
StringBuilder sb = new StringBuilder("");
try {
br = request.getReader();
String str;
while ((str = br.readLine()) != null) {
sb.append(str);
}
br.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != br) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return sb.toString();
}
}
消费者和服务提供者都需要创建User实体。
public class User implements Serializable{
private static final long serialVersionUID = -3653242135661883164L;
private Integer id;
private String name;
private Integer age;
public User() {
}
public User(String name, Integer age) {
super();
this.name = name;
this.age = age;
}
public User(Integer id, String name, Integer age) {
super();
this.id = id;
this.name = name;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
}
}