SpringMVC RestTemplate的几种请求调用
1.用统一的方法模板进行四种请求：POST,PUT,DELETE,GET
restTemplate.exchange(
String url,
HttpMethod method,
HttpEntity requestEntity,
Class responseType,
Object uriVariables[]
)
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
例如：
(1)POST请求
String reqJsonStr = "{\"code\":\"testCode\", \"group\":\"testGroup\",\"content\":\"testContent\", \"order\":1}";
HttpHeaders headers = new HttpHeaders(); headers.setContentType(MediaType.APPLICATION_JSON);
HttpEntity<String> entity = new HttpEntity<String>(reqJsonStr,headers);
ResponseEntity<Map> resp = restTemplate.exchange(DIC_DATA_URL, HttpMethod.POST, entity, Map.class);
(2)PUT请求
String reqJsonStr = "{\"id\":227,\"code\":\"updateCC\", \"group\":\"UPDATE\",\"content\":\"updateCT\", \"order\":9}";
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
HttpEntity<String> entity = new HttpEntity<String>(reqJsonStr,headers);
ResponseEntity<Map> resp = restTemplate.exchange(DIC_DATA_URL, HttpMethod.PUT, entity, Map.class);
(3)DELETE请求
ResponseEntity<Map> resp = restTemplate.exchange(DIC_DATA_URL + "?id={id}", HttpMethod.DELETE, null, Map.class, 227);
(4)GET请求
ResponseEntity<String> results = restTemplate.exchange(url,HttpMethod.GET, null, String.class, params);
2.用各种请求对应的专一接口
(1)POST请求
postForObject(String url, Object request, Class responseType, Object uriVariables[]):
返回数据对象Object，例如：
DicData data = new DicData();
data.setCode("cd123"); data.setGroup("TEST"); data.setContent("测试数据"); data.setOrder(5);
DicData obj = restTemplate.postForObject(DIC_DATA_URL, data, DicData.class);
> 或者
postForEntity:(String url, Object request, Class responseType, Object uriVariables[])
返回封装了数据对象的ResponseEntity对象，例如：
DicData data = new DicData();
data.setCode("cd123"); data.setGroup("TEST"); data.setContent("测试数据"); data.setOrder(5);
ResponseEntity<Map> respEntity = restTemplate.postForEntity(DIC_DATA_URL, data, Map.class);
> (2)PUT请求
put(String url, Object request, Object urlVariables[])
例如：
DicData data = new DicData();
data.setId(226L); data.setCode("updateCode"); data.setGroup("UPDATE");
data.setContent("测试数据"); data.setOrder(9);
restTemplate.put(DIC_DATA_URL, data);
> (3)DELETE请求
delete(String url, Object urlVariables[])
例如：
restTemplate.delete(DIC_DATA_URL + "?id={id}", 222);
> (4)GET请求
getForObject(String url, Class responseType, Object urlVariables[])：
返回请求的结果对象，例如
Order o = restTemplate.getForObject(Constants.SERVER_URL+"/order?orderCode={orderCode}",
Order.class,order.getOrderCode());
getForEntity(String url, Class responseType, Object urlVariables[])：
返回封装了数据对象的ResponseEntity对象，例如：
ResponseEntity<EBTUser> ebtuserResponse = restTemplate.getForEntity(url,EBTUser.class);
EBTUser user = ebtuserResponse.getBody();
3.GET请求,要返回一些复合数据类型时的处理
> (1)返回List类型数据
DicData[] dicResult = restTemplate.getForObject( Constants.SERVER_URL + "/dicDatas/dicData?"
+ "group={group}", DicData[].class, group);
List<DicData> list = Arrays.asList(dicResult);
或者
//ParameterizedTypeReference解决单层不嵌套以及嵌套的list
// pass generic information to resttemplate; ParameterizedTypeReference为spring3.2版本后引进的类
ParameterizedTypeReference<List<DicData>> responseType = new ParameterizedTypeReference<List<DicData>>();
ResponseEntity<List<DicData>> resp = restTemplate.exchange(Constants.SERVER_URL + "/dicDatas/dicData?group={group}",
HttpMethod.GET, null, responseType);
List<DicData> list = resp.getBody();
> (2)返回属性中有范型数据的复合对象
//ObjectMapper 解析嵌套的list变成的json字符串,TypeReference
比如，分页对象
ResponseEntity<String> 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<Product> page = mapper.readValue(results.getBody(), new TypeReference<PageInfo<Product>>() { });