RestTemplate使用教程

原文地址：https://www.cnblogs.com/f-anything/p/10084215.html

一、概述

spring框架提供的RestTemplate类可用于在应用中调用rest服务，它简化了与http服务的通信方式，统一了RESTful的标准，封装了http链接，我们只需要传入url及返回值类型即可。相较于之前常用的HttpClient，RestTemplate是一种更优雅的调用RESTful服务的方式。

在Spring应用程序中访问第三方REST服务与使用Spring RestTemplate类有关。RestTemplate类的设计原则与许多其他Spring *模板类(例如JdbcTemplate、JmsTemplate)相同，为执行复杂任务提供了一种具有默认行为的简化方法。

RestTemplate默认依赖JDK提供http连接的能力（HttpURLConnection），如果有需要的话也可以通过setRequestFactory方法替换为例如 Apache HttpComponents、Netty或OkHttp等其它HTTP library。

考虑到RestTemplate类是为调用REST服务而设计的，因此它的主要方法与REST的基础紧密相连就不足为奇了，后者是HTTP协议的方法:HEAD、GET、POST、PUT、DELETE和OPTIONS。例如，RestTemplate类具有headForHeaders()、getForObject()、postForObject()、put()和delete()等方法。

二、实现

RestTemplate包含以下几个部分：

HttpMessageConverter 对象转换器
ClientHttpRequestFactory 默认是JDK的HttpURLConnection
ResponseErrorHandler 异常处理
ClientHttpRequestInterceptor 请求拦截器

常规配置

public MyRestClientService(RestTemplateBuilder restTemplateBuilder) {

        this.restTemplate = restTemplateBuilder

            .basicAuthorization("username", "password")

            .setConnectTimeout(3000)

            .setReadTimeout(5000)

            .rootUri("http://api.example.com/")

            .build();

    }

ClientHttpRequestInterceptor

学习使用带有Spring RestTemplate的ClientHttpRequestInterceptor，以Spring AOP风格记录请求和响应头和主体。

拦截器记录请求和响应

import org.slf4j.Logger;import org.slf4j.LoggerFactory;

import org.springframework.http.HttpRequest;

import org.springframework.http.client.ClientHttpRequestExecution;

import org.springframework.http.client.ClientHttpRequestInterceptor;

import org.springframework.http.client.ClientHttpResponse;

import org.springframework.util.StreamUtils;

import java.io.IOException;

import java.nio.charset.Charset;

public class RequestResponseLoggingInterceptor implements ClientHttpRequestInterceptor {

    private final Logger log = LoggerFactory.getLogger(this.getClass());

    @Override

    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException

    {

        logRequest(request, body);

        ClientHttpResponse response = execution.execute(request, body);

        logResponse(response);

        //Add optional additional headers

        response.getHeaders().add("headerName", "VALUE");

        return response;

    }

    private void logRequest(HttpRequest request, byte[] body) throws IOException

    {

        if (log.isDebugEnabled())

        {

            log.debug("===========================request begin================================================");

            log.debug("URI         : {}", request.getURI());

            log.debug("Method      : {}", request.getMethod());

            log.debug("Headers     : {}", request.getHeaders());

            log.debug("Request body: {}", new String(body, "UTF-8"));

            log.debug("==========================request end================================================");

        }

    }

    private void logResponse(ClientHttpResponse response) throws IOException

    {

        if (log.isDebugEnabled())

        {

            log.debug("============================response begin==========================================");

            log.debug("Status code  : {}", response.getStatusCode());

            log.debug("Status text  : {}", response.getStatusText());

            log.debug("Headers      : {}", response.getHeaders());

            log.debug("Response body: {}", StreamUtils.copyToString(response.getBody(), Charset.defaultCharset()));

            log.debug("=======================response end=================================================");

        }

    }

}

注册ClientHttpRequestInterceptor

@Bean

public RestTemplate restTemplate(){

    RestTemplate restTemplate = new RestTemplate();

    restTemplate.setRequestFactory(newBufferingClientHttpRequestFactory(clientHttpRequestFactory()));

    restTemplate.setMessageConverters(Collections.singletonList(mappingJacksonHttpMessageConverter()));

    restTemplate.setInterceptors( Collections.singletonList(newRequestResponseLoggingInterceptor()) );

    return restTemplate;

}

三、请求示例

GET

private static void getEmployees(){

    final String uri = "http://localhost:8080/springrestexample/employees";

    RestTemplate restTemplate = new RestTemplate();

    String result = restTemplate.getForObject(uri, String.class);

    System.out.println(result);

}

使用RestTemplate定制HTTP头文件

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);

}

Get请求获取响应为一个对象

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);

}

URL 参数

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);

}

POST

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);

}

Submit Form Data

HttpHeaders headers = new HttpHeaders();

headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

MultiValueMap<String, String> map= new LinkedMultiValueMap<>();

map.add("id", "1");

HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);

RestTemplate restTemplate = new RestTemplate();

EmployeeVO result = restTemplate.postForObject( uri, request, EmployeeVO.class);

System.out.println(result);

PUT

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);

}

Simple PUT

Foo updatedInstance = new Foo("newName");

updatedInstance.setId(createResponse.getBody().getId());

String resourceUrl =

  fooResourceUrl + '/' + createResponse.getBody().getId();

HttpEntity<Foo> requestUpdate = new HttpEntity<>(updatedInstance, headers);

template.exchange(resourceUrl, HttpMethod.PUT, requestUpdate, Void.class);

使用.exchange和请求回调

RequestCallback requestCallback(final Foo updatedInstance) {

    return clientHttpRequest -> {

        ObjectMapper mapper = new ObjectMapper();

        mapper.writeValue(clientHttpRequest.getBody(), updatedInstance);

        clientHttpRequest.getHeaders().add(

          HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);

        clientHttpRequest.getHeaders().add(

          HttpHeaders.AUTHORIZATION, "Basic " + getBase64EncodedLogPass());

    };

}

DELETE

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 );

}

参考资料：

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

https://www.xncoding.com/2017/07/06/spring/sb-restclient.html

https://www.baeldung.com/rest-template