Spring `RestTemplate` – Spring REST 客户端示例

原文： https://howtodoinjava.com/spring-boot2/resttemplate/spring-restful-client-resttemplate-example/

在学习为 XML 表示形式和 JSON 表示形式构建 Spring REST API 之后，让我们构建 Spring REST 客户端以使用我们编写的 API 在链接的示例中。

在 Spring 应用程序内部访问第三方 REST 服务的过程涉及 Spring RestTemplate类的使用。 RestTemplate类的设计原理与许多其他 Spring *Template类（例如JdbcTemplate和JmsTemplate）相同，为执行复杂任务提供了具有默认行为的简化方法。

鉴于RestTemplate类是为调用 REST 服务设计的，因此它的主要方法与 REST 的基础紧密结合在一起就不足为奇了，REST 的基础是 HTTP 协议的方法：HEAD，GET，POST，PUT，DELETE 和 OPTION。 例如，RestTemplate类具有方法headForHeaders()，getForObject()，postForObject()，put()和delete()等。

阅读更多和源代码： Spring REST 示例 – JSON

阅读更多：带有 HttpClient 的 RestTemplate Java 配置

1. Spring RestTemplate – HTTP GET 方法示例

1.1. XML 响应

REST API 代码

用于 HTTP GET 方法的 Spring REST API。

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_XML_VALUE, method = RequestMethod.GET)
public String getAllEmployeesXML(Model model) 
{
    model.addAttribute("employees", getEmployeesCollection());
    return "xmlTemplate";
}

REST 客户端代码

Spring REST 客户端使用RestTemplate访问 HTTP GET api 请求。

private static void getEmployees()
{
    final String uri = "http://localhost:8080/springrestexample/employees.xml";
    RestTemplate restTemplate = new RestTemplate();
    String result = restTemplate.getForObject(uri, String.class);
    System.out.println(result);
}

1.2. JSON 响应

REST API 代码

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_JSON_VALUE,  method = RequestMethod.GET)
public String getAllEmployeesJSON(Model model) 
{
    model.addAttribute("employees", getEmployeesCollection());
    return "jsonTemplate";
}

REST 客户端代码

private static void getEmployees()
{
    final String uri = "http://localhost:8080/springrestexample/employees.json";
    RestTemplate restTemplate = new RestTemplate();
    String result = restTemplate.getForObject(uri, String.class);
    System.out.println(result);
}

1.3. 使用RestTemplate的自定义 HTTP 标头

REST API 代码

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_JSON_VALUE,  method = RequestMethod.GET)
public String getAllEmployeesJSON(Model model) 
{
    model.addAttribute("employees", getEmployeesCollection());
    return "jsonTemplate";
}

REST 客户端代码

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);
}

1.4. 获取响应作为对象

REST API 代码

@RequestMapping(value = "/employees", produces = MediaType.APPLICATION_XML_VALUE, method = RequestMethod.GET)
public String getAllEmployeesXML(Model model) 
{
    model.addAttribute("employees", getEmployeesCollection());
    return "xmlTemplate";
}

REST 客户端代码

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);
}

1.5. URL 参数

REST API 代码

@RequestMapping(value = "/employees/{id}")
public ResponseEntity<EmployeeVO> getEmployeeById (@PathVariable("id") int id) 
{
    if (id <= 3) {
        EmployeeVO employee = new EmployeeVO(1,"Lokesh","Gupta","howtodoinjava@gmail.com");
        return new ResponseEntity<EmployeeVO>(employee, HttpStatus.OK);
    }
    return new ResponseEntity(HttpStatus.NOT_FOUND);
}

REST 客户端代码

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);
}

2. Spring RestTemplate – HTTP POST 方法示例

REST API 代码

用于 HTTP POST 方法的 Spring REST API。

@RequestMapping(value = "/employees", method = RequestMethod.POST)
public ResponseEntity<String> createEmployee(@RequestBody EmployeeVO employee) 
{
    System.out.println(employee);
    return new ResponseEntity(HttpStatus.CREATED);
}

REST 客户端代码

Spring REST 客户端使用RestTemplate访问 HTTP POST api 请求。

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);
}

3. Spring RestTemplate – HTTP PUT 方法示例

REST API 代码

用于 HTTP PUT 方法的 Spring REST API。

@RequestMapping(value = "/employees/{id}", method = RequestMethod.PUT)
public ResponseEntity<EmployeeVO> updateEmployee(@PathVariable("id") int id, @RequestBody EmployeeVO employee) 
{
    System.out.println(id);
    System.out.println(employee);
    return new ResponseEntity<EmployeeVO>(employee, HttpStatus.OK);
}

REST 客户端代码

Spring REST 客户端使用RestTemplate访问 HTTP PUT api 请求。

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);
}

4. Spring RestTemplate – HTTP DELETE 方法示例

REST API 代码

用于 HTTP DELETE 方法的 Spring REST API。

@RequestMapping(value = "/employees/{id}", method = RequestMethod.DELETE)
public ResponseEntity<String> updateEmployee(@PathVariable("id") int id) 
{
    System.out.println(id);
    return new ResponseEntity(HttpStatus.OK);
}

REST 客户端代码

Spring REST 客户端使用RestTemplate访问 HTTP DELETE api 请求。

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 );
}

随意复制和修改以上 Spring RestTemplate示例，以在您的 MVC 应用程序中构建 Spring REST 客户端

5. 更多的RestTemplate示例

Spring RestTemplate基本身份验证示例
Spring RestTemplate超时配置示例
Spring RestTemplateBuilder示例
Spring RestTemplate – HttpClient配置示例
Spring Boot RestTemplate GET 示例
Spring Boot RestTemplate POST 示例
带有RestTemplate的 Spring Boot JUnit 示例
带有标头的 Spring boot TestRestTemplate POST 示例
带有RestTemplate的 Spring ClientHttpRequestInterceptor

学习愉快！