這里寫目錄標題

• 前言
• 準備
• • • 引入 lib
    • 創建 RestTemplate Bean
• 認識一下RestTemplate
• getForObject 示例
• • • 簡單調用
    • 參數拼接
• postForEntity 示例
• • • 構造 request Object
    • 在 URL 中傳參
• postForObject 示例
• • • 構造 request Object
    • 在 URL 中傳參
• (POST)Content-Type: application/x-www-form-urlencoded
• (POST)Content-Type: application/json
• (POST)Content-Type: application/json
• postForEntity 與 postForObject 的區別

前言

• spring-boot 2.0.0.RELEASE
• spring-web 5.0.4.RELEASE
• maven 3.5.0
• Eclipse Version: 2019-09 R (4.13.0)
• 使用 RestTemplate 調用 restful 接口
• 官方說明在這里和這里

準備

引入 lib

RestTemplate 類的完整路徑為 ： org.springframework.web.client.RestTemplate 。
RestTemplate 類在 lib : spring-web 中。

springboot項目引入 lib：

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId> </dependency>

創建 RestTemplate Bean

@Configuration public class RestTemplateConfig {@Beanpublic RestTemplate getRestTemplate() {return new RestTemplate();} }

說明：

• 也可以不創建Bean。不創建Bean時，需要每次new RestTemplate()。
• 如果既不創建Bean，也不每次new RestTemplate()，則會遇到錯誤No qualifying bean of type 'org.springframework.web.client.RestTemplate'

認識一下RestTemplate

常用方法，getForEntity和getForObject方法、postForEntity和postForObject方法。ForEntity方法和ForObject方法的差別在于返回值。ResponseEntity類型的返回值可以獲取到完整的Response信息，比如header、http status。部分相關方法定義：

• public <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType) throws RestClientException
• public <T> T getForObject(URI url, Class<T> responseType) throws RestClientException
• public <T> ResponseEntity<T> postForEntity(URI url, @Nullable Object request, Class<T> responseType) throws RestClientException
• public <T> T postForObject(URI url, @Nullable Object request, Class<T> responseType) throws RestClientException

exchange方法更偏向于自己處理RequestEntity的情況。

getForObject 示例

簡單調用

String url = "https://www.so.com/s?q=abc"; // 將url返回的內容，存入變量result中 String result = this.restTemplate.getForObject(url, String.class);

參數拼接

String url = "https://www.so.com/s?q={keyword}"; Map<String, String> paramMap = new HashMap<>(); paramMap.put("keyword", "abc"); // 將url返回的內容，存入變量result中 String result = this.restTemplate.getForObject(url, String.class, paramMap);

postForEntity 示例

構造 request Object

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept";HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);MultiValueMap<String, String> paramMap= new LinkedMultiValueMap<>();paramMap.add("name", "zhangsan");HttpEntity<MultiValueMap<String, String>> entity = null;entity = new HttpEntity<>(paramMap, headers);ResponseEntity<String> exchange = this.restTemplate.postForEntity(url, entity, String.class);String result = exchange.getBody();System.out.println(result);} }

在 URL 中傳參

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept?name={name}";ResponseEntity<String> exchange = this.restTemplate.postForEntity(url, null, String.class, "zhangsan");System.out.println(exchange.getBody());} }

postForObject 示例

構造 request Object

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept";HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);MultiValueMap<String, String> paramMap= new LinkedMultiValueMap<>();paramMap.add("name", "zhangsan");HttpEntity<MultiValueMap<String, String>> entity = null;entity = new HttpEntity<>(paramMap, headers);String result = this.restTemplate.postForObject(url, entity, String.class);System.out.println(result);} }

在 URL 中傳參

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept?name={name}";String result = this.restTemplate.postForObject(url, null, String.class, "zhangsan");System.out.println(result);} }

(POST)Content-Type: application/x-www-form-urlencoded

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept";HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);MultiValueMap<String, String> paramMap= new LinkedMultiValueMap<>();paramMap.add("name", "zhangsan");HttpEntity<MultiValueMap<String, String>> entity = null;entity = new HttpEntity<>(paramMap, headers);String result = this.restTemplate.postForObject(url, entity, String.class);System.out.println(result);} }

(POST)Content-Type: application/json

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept";HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_JSON);JSONObject jsonBody = new JSONObject();jsonBody.put("name", "zhangsan");jsonBody.put("age", 18);HttpEntity<JSONObject> entity = null;entity = new HttpEntity<>(jsonBody , headers);String result = this.restTemplate.postForObject(url, entity, String.class);System.out.println(result);} }

(POST)Content-Type: application/json

@Service public class DataSendService {@Autowiredprivate RestTemplate restTemplate;public void sendData() {String url = "http://localhost:8080/app/data-accept";HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.TEXT_PLAIN);String message = "this is a text";HttpEntity<String > entity = null;entity = new HttpEntity<>(message , headers);String result = this.restTemplate.postForObject(url, entity, String.class);System.out.println(result);} }

postForEntity 與 postForObject 的區別

參數一樣，功能一樣，返回值類型不一樣。

public <T> T postForObject(String url, @Nullable Object request, Class<T> responseType,Object... uriVariables) throws RestClientException {... } public <T> T postForObject(String url, @Nullable Object request, Class<T> responseType,Map<String, ?> uriVariables) throws RestClientException {... } public <T> T postForObject(URI url, @Nullable Object request, Class<T> responseType)throws RestClientException {... } public <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request,Class<T> responseType, Object... uriVariables) throws RestClientException {... } public <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request,Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {... } @Override public <T> ResponseEntity<T> postForEntity(URI url, @Nullable Object request, Class<T> responseType)throws RestClientException {... }

總結

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