RestTemplate使用详解

在开发中有时候经常需要一些Http请求，请求数据，下载内容，也有一些简单的分布式应用直接使用Http请求作为跨应用的交互协议。

在Java中有不同的Http请求方式，主要就是HttpURLConnection或者ApacheHttpClient，但是这两个用起来都感觉有那么一点点的复杂；

好在Spring内置了RestTemplate作为Http请求的工具类，简化了很多操作，虽然Spring5推出了WebClient，但是整体感觉还是RestTemplate用起来更简单方便一些。

这里记录分享下RestTemplate的常见使用方式，RestTemplate作为Java中最简单好用的Http请求工具类一定要了解一下

常见用法

简单Get\Post请求

@Test
    public void testGetPost(){
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.getMessageConverters().add(new FastJsonHttpMessageConverter()); String res = restTemplate.postForObject("http://test.aihe.space/", null, String.class);
        System.out.println(res); String res2 = restTemplate.getForObject("http://test.aihe.space/", String.class);
        System.out.println(res2);
    }

Post提交常规表单

@Test
    public void testPostFrom(){
        RestTemplate restTemplate = new RestTemplate();
        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); String fooResourceUrl = "http://test.aihe.space/";
        ResponseEntity<String> response = restTemplate.postForEntity(fooResourceUrl, request, String.class);
        System.out.println(response.getStatusCode());
        System.out.println(response.getBody());
    }

Post上传文件

注意：上传文件时的value为FileSystemResource

@Test
    public void testPostFile(){

        RestTemplate restTemplate = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        MultiValueMap<String, Object> map= new LinkedMultiValueMap<>();
        map.add("id", "1");
        map.add("file",new FileSystemResource("/Users/aihe/code/init/src/test/java/me/aihe/RestTemplateTest.java"));
        HttpEntity<MultiValueMap<String, Object>> request = new HttpEntity<>(map, headers); String fooResourceUrl = "http://test.aihe.space/";
        ResponseEntity<String> response = restTemplate.postForEntity(fooResourceUrl, request, String.class);
        System.out.println(response.getStatusCode());
        System.out.println(response.getBody());
    }

配置项

请求添加Cookie\Header

@Test public void testCookieHeader(){

        RestTemplate restTemplate = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        MultiValueMap<String, Object> map= new LinkedMultiValueMap<>(); // 常见的Header都可以直接设置 //        headers.set headers.set("custom1","customValue1"); // 设置Cookie headers.set(HttpHeaders.COOKIE,"xxxx"); map.add("id", "1");
        HttpEntity<MultiValueMap<String, Object>> request = new HttpEntity<>(map, headers);
        String fooResourceUrl = "http://test.aihe.space/";
        ResponseEntity<String> response = restTemplate.postForEntity(fooResourceUrl, request, String.class);
        System.out.println(response.getStatusCode());
        System.out.println(response.getBody());
    }

配置请求工厂超时、代理

使用Rest请求的时候注意设置超时时间

@Test
    public void testHttpFactory(){
        RestTemplate restTemplate = new RestTemplate();
        SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
        requestFactory.setReadTimeout(5000);
        requestFactory.setConnectTimeout(3000); Proxy proxy = new Proxy(Proxy.Type.SOCKS, new InetSocketAddress("127.0.0.1", 7890));

        requestFactory.setProxy(proxy);
        restTemplate.setRequestFactory(requestFactory);

        restTemplate.getMessageConverters().add(new FastJsonHttpMessageConverter()); String res = restTemplate.postForObject("http://test.aihe.space/", null, String.class);
        System.out.println(res);
    }

配置拦截器、转换器，错误处理

@Test public void testConverterInterceptor(){
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.setInterceptors(Collections.singletonList(new BasicAuthenticationInterceptor("admin","admin")));
        restTemplate.getMessageConverters().add(new FastJsonHttpMessageConverter());
        restTemplate.setErrorHandler(new DefaultResponseErrorHandler());
        String res = restTemplate.postForObject("http://test.aihe.space/", null, String.class);
        System.out.println(res);
    }

错误重试(额外)

可以考虑使用Spring Retry，但是相当于引入了新的东西，如果没有特殊必要，可以自己简单用for循环做下；

// Spring Retry方式 @Bean public RetryTemplate retryTemplate() { int maxAttempt = Integer.parseInt(env.getProperty("maxAttempt")); int retryTimeInterval = Integer.parseInt(env.getProperty("retryTimeInterval"));

    SimpleRetryPolicy retryPolicy = new SimpleRetryPolicy();
    retryPolicy.setMaxAttempts(maxAttempt);

    FixedBackOffPolicy backOffPolicy = new FixedBackOffPolicy(); // 失败的间隔 backOffPolicy.setBackOffPeriod(retryTimeInterval); 

    RetryTemplate template = new RetryTemplate(); template.setRetryPolicy(retryPolicy); template.setBackOffPolicy(backOffPolicy); return template;
  }

SSL请求

参考：stackoverflow.com/questions/1…

@Test public void testSSL() throws FileNotFoundException, NoSuchAlgorithmException, KeyStoreException, UnrecoverableKeyException {
        String keyStorePassword = "123456";
        KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
        keyStore.load(new FileInputStream(new File("keyStoreFile")),
                keyStorePassword.toCharArray());

        SSLConnectionSocketFactory socketFactory = new SSLConnectionSocketFactory( new SSLContextBuilder()
                        .loadTrustMaterial(null, new TrustSelfSignedStrategy())
                        .loadKeyMaterial(keyStore, keyStorePassword.toCharArray())
                        .build(),
                NoopHostnameVerifier.INSTANCE);

        HttpClient httpClient = HttpClients.custom().setSSLSocketFactory(
                socketFactory).build();

        ClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(
                httpClient);
        RestTemplate restTemplate = new RestTemplate(requestFactory);
        String res = restTemplate.postForObject("http://test.aihe.space/", null, String.class);
        System.out.println(res);
    }

基于RestTemplate一些工具

钉钉机器人通知

可以支持发送普通文本、ActionCard，Markdown的消息

import java.util.ArrayList; import java.util.List; import lombok.Data; import lombok.Getter; import lombok.extern.slf4j.Slf4j; import org.springframework.http.ResponseEntity; import org.springframework.web.client.RestTemplate; /**
 * 使用场景：
 * 功能描述：https://developers.dingtalk.com/document/app/custom-robot-access/title-72m-8ag-pqw
 */ @Slf4j public class RobotUtils { private static RestTemplate restTemplate = new RestTemplate(); private static String URL = ""; public static void main(String[] args) {
        sendMarkDownMsg(
            URL, "测试", "测试", new ArrayList<>()
        );
    } /**
     * {
     * "msgtype": "text",
     * "text": {
     * "content": "我就是我, @150XXXXXXXX 是不一样的烟火"
     * },
     * "at": {
     * "atMobiles": [
     * "150XXXXXXXX"
     * ],
     * "isAtAll": false
     * }
     * }
     */ public static void sendTextMsg(String url, String content, List<String> atPerson) {
        RobotMsg robotMsg = new RobotMsg();
        robotMsg.setMsgtype("text");

        RobotAt robotAt = new RobotAt();
        robotAt.setAtAll(false); if (atPerson != null && atPerson.size() > 0) {
            robotAt.setAtMobiles(atPerson);
        }
        robotMsg.setAt(robotAt);

        RobotText robotText = new RobotText();
        robotText.setContent(content);

        robotMsg.setText(robotText);
        ResponseEntity<String> responseEntity = restTemplate.postForEntity(url, robotMsg, String.class);
        log.info("sendTextMsg {}",responseEntity.getBody());
    } /**
     * @param url            机器人地址
     * @param title          actionCard标题
     * @param text           缩略内容
     * @param vertical 按钮方向
     * @param btns           按钮内容
     */ public static void sendActionCardMsg(String url, String title, String text, Boolean vertical, List<RobotBtn> btns) {
        RobotMsg robotMsg = new RobotMsg();
        robotMsg.setMsgtype("actionCard");

        RobotAt robotAt = new RobotAt();
        robotAt.setAtAll(false);

        RobotActionCard robotActionCard
            = new RobotActionCard();
        robotActionCard.setTitle(title);
        robotActionCard.setText(text);
        robotActionCard.setBtnOrientation((vertical == null || vertical) ? "0" : "1");
        robotActionCard.setBtns(btns);

        robotMsg.setActionCard(robotActionCard);
        ResponseEntity<String> responseEntity = restTemplate.postForEntity(url, robotMsg, String.class);
        System.out.println(responseEntity.getBody());
    } public static void sendMarkDownMsg(String url,String title,String text,List<String> atPerson){
        RobotMarkDownMsg markDownMsg = new RobotMarkDownMsg();
        markDownMsg.setMsgtype("markdown");

        RobotAt robotAt = new RobotAt();
        robotAt.setAtAll(false); if (atPerson != null && atPerson.size() > 0) {
            robotAt.setAtMobiles(atPerson);
        }
        markDownMsg.setAt(robotAt);

        RobotMarkdownText markdownText = new RobotMarkdownText();
        markdownText.setTitle(title);
        markdownText.setText(text);
        markDownMsg.setMarkdown(markdownText);
        ResponseEntity<String> responseEntity = restTemplate.postForEntity(url, markDownMsg, String.class);
        System.out.println(responseEntity.getBody());
    } public enum SupportRobotEnum { /**
         * 测试机器人群
         */ CESHI("测试机器人群", ""); @Getter private String desc; @Getter private String url;

        SupportRobotEnum(String desc, String url) { this.desc = desc; this.url = url;
        }
    } @Data public static class RobotAt { public List<String> atMobiles; public boolean isAtAll;

    } @Data public static class RobotMarkDownMsg{ public String msgtype; public RobotAt at; public RobotMarkdownText markdown;
    } @Data public static class RobotMarkdownText {
        String title;
        String text;
    } @Data public static class RobotMsg { public String msgtype; public RobotAt at; /**
         * 普通文字消息类型消息
         */ public RobotText text; /**
         * actionCard类型消息时支持
         */ public RobotActionCard actionCard;

    } @Data public static class RobotText { public String content;

    } @Data public static class RobotActionCard { public String title; public String text; public String hideAvatar; public String btnOrientation; public List<RobotBtn> btns;

    } @Data public static class RobotBtn { public String title; public String actionURL; public static RobotBtn buildBtn(String title, String actionUrl) {
            RobotBtn robotBtn = new RobotBtn();
            robotBtn.setActionURL(actionUrl);
            robotBtn.setTitle(title); return robotBtn;
        }
    }
}