HttpClient VS RestTemplate

在日常项目开发中，有时候我们需要调用第三方接口数据，常用的方法有传统JDK自带的URLConnection，Apache Jakarta Common下的子项目HttpClient ，Spring的RestTemplate。
在SpringBoot项目下，使用不同的方式调用心知天气接口，具体接口文档地址

一、HttpClient

【步骤】：
1）创建一个httpclient对象，注意以下版本问题说明
HttpClient4.0版本前：HttpClient httpClient = new DefaultHttpClient();
4.0版本后:CloseableHttpClient httpClient = HttpClientBuilder.create().build();
2）创建一个httpGet对象
HttpGet request = new HttpGet(uri);
3）执行请求调用httpclient的execute(),传入httpGet对象，返回CloseableHttpResponse response = httpClient.execute(request, HttpClientContext.create());
4）取得响应结果并处理
5）关闭HttpClient
response.close();
httpClient.close();
1.1、添加依赖
Gradle:

compile ('org.apache.httpcomponents:httpclient:4.5.3')

Maven:

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.3</version>
</dependency>

1.2 在Controller中使用HttpClient 调用心知天气接口（注意在日常开发中，不要在Controller下写太多业务逻辑代码，尽可能把业务逻辑代码写在Service中）

    @ApiOperation(value = "HttpClient获取天气")
    @GetMapping(value = "/v1/weather", consumes = MediaType.ALL_VALUE)
    public ResponseEntity<String> getWeather(@ApiParam(value = "语言(zh-Hans：简体中文/zh-Hant：繁体中文)") @RequestParam(value = "language") String language,
                                             @ApiParam(value = "地址") @RequestParam(value = "location") String location) throws URISyntaxException, IOException {
        URI uri = new URIBuilder()
                .setScheme("https").setHost("api.seniverse.com").setPath("/v3/weather/now.json")
                .setParameter("key", "w99tf57ghc86thhv")
                .setParameter("language", language)
                .setParameter("location", location)
                .build();
        // 1.创建一个httpclient对象
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        // 2.创建一个httpGet对象
        HttpGet request = new HttpGet(uri);
        CloseableHttpResponse response = null;

        try {
            // 3.执行请求调用httpclient的execute(),传入httpGet对象，返回CloseableHttpResponse
            response = httpClient.execute(request, HttpClientContext.create());
            // 4.取得响应结果并处理
            HttpEntity entity = response.getEntity();
            String responseString = EntityUtils.toString(entity);
            HttpHeaders httpHeaders = new HttpHeaders();
            for (Header header : response.getAllHeaders()) {
                httpHeaders.add(header.getName(), header.getValue());
            }
            int statusCode = response.getStatusLine().getStatusCode();
            EntityUtils.consume(entity);

            return new ResponseEntity<>(responseString, httpHeaders, HttpStatus.valueOf(statusCode));
        } finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException ignored) {
                }
            }
            httpClient.close();
        }
    }

1.3 在浏览器输入 http://localhost:8080/v1/weather?language=zh-Hans&location=beijing 注意v1前的相关信息根据自己的实际端口修改。运行效果如图：

image.png

二、RestTemplate

2.1 在SpringBoot主方法中先注册Bean

@Bean
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }

2.2 在控制器中使用RestTemplate调用天气接口

    @Autowired
    private RestTemplate restTemplate;

    @ApiOperation(value = "RestTemplate获取天气")
    @GetMapping(value = "/v2/weather", consumes = MediaType.ALL_VALUE)
    public Object weather(@ApiParam(value = "语言") @RequestParam(value = "language") String language, @ApiParam(value = "地址") @RequestParam(value = "location") String location) throws URISyntaxException, IOException {
        URI uri = new URIBuilder()
                .setScheme("https").setHost("api.seniverse.com").setPath("/v3/weather/now.json")
                .setParameter("key", "w99tf57ghc86thhv")
                .setParameter("language", language)
                .setParameter("location", location)
                .build();
        return restTemplate.getForObject(uri, Object.class);
    }

同理，在浏览器输入 http://localhost:8080/v2/weather?language=zh-Hans&location=beijing 注意v2前的相关信息根据自己的实际端口修改。运行效果如图：

image.png
相比于HttpClient，RestTemplate使用起来更简便。
详解 RestTemplate 操作
RestTemplate 深度解析
另外，在SpringCloud中，加了@LoadBalanced注解的RestTemplate还搭配Ribbon实现了负载均衡。