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使用RestTemplate进行HTTP请求的服务端开发

概述

Http请求在服务端开发中是必不可少的，本文将使用Spring Boot中的RestTemplate作为门面，HttpClient作为实现，演示基础的Http请求例子。

源码分析

1. 添加pom.xml依赖

RestTemplate在Spring-Web模块中内置，Spring Boot会自动引入。以下是需要添加的依赖：

   
    
    
     org.apache.httpcomponents
    
    
    
     httpclient
    
    
    
     4.5.5
    
   
   
   
    
    
     io.netty
    
    
    
     netty-all
    
    
    
     4.1.5.Final
    
   
   
    
    
     org.springframework.boot
    
    
    
     spring-boot-configuration-processor
    
    
    
     true
    
   

2. 配置文件application.yml（可选）

# yml配置的优先级高于java配置；如果yml配置和java配置同时存在，则yml配置会覆盖java配置
spring:
    restTemplate:
        maxTotalConnect: 1000 #连接池的最大连接数，0代表不限；如果取0，需要考虑连接泄露导致系统崩溃的后果
        maxConnectPerRoute: 200
        connectTimeout: 3000
        readTimeout: 5000
        charset: UTF-8

3. 编写RestTemplate配置（必备）

@Configuration
@ConfigurationProperties(prefix = "spring.restTemplate")
@ConditionalOnClass(value = {RestTemplate.class, CloseableHttpClient.class})
public class RestTemplateConfig {
    // java配置的优先级低于yml配置；如果yml配置不存在，会采用java配置
    private int maxTotalConnection = 500;
    private int maxConnectionPerRoute = 100;
    private int connectionTimeout = 2000;
    private int readTimeout = 30000;
    private String charset = "UTF-8";
    public void setMaxTotalConnection(int maxTotalConnection) {
        this.maxTotalConnection = maxTotalConnection;
    }
    public void setMaxConnectionPerRoute(int maxConnectionPerRoute) {
        this.maxConnectionPerRoute = maxConnectionPerRoute;
    }
    public void setConnectionTimeout(int connectionTimeout) {
        this.connectionTimeout = connectionTimeout;
    }
    public void setReadTimeout(int readTimeout) {
        this.readTimeout = readTimeout;
    }
    public void setCharset(String charset) {
        this.charset = charset;
    }
    @Bean(name = "clientHttpRequestFactory")
    public ClientHttpRequestFactory clientHttpRequestFactory() {
        return createClientHttpRequestFactory(this.connectionTimeout, this.readTimeout);
    }
    @Bean(name = "restTemplate")
    @ConditionalOnMissingBean(RestTemplate.class)
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        return createRestTemplate(factory);
    }
    @Bean(name = "asyncRestTemplate")
    @ConditionalOnMissingBean(AsyncRestTemplate.class)
    public AsyncRestTemplate asyncRestTemplate(RestTemplate restTemplate) {
        final Netty4ClientHttpRequestFactory factory = new Netty4ClientHttpRequestFactory();
        factory.setConnectTimeout(this.connectionTimeout);
        factory.setReadTimeout(this.readTimeout);
        return new AsyncRestTemplate(factory, restTemplate);
    }
    private ClientHttpRequestFactory createClientHttpRequestFactory(int connectionTimeout, int readTimeout) {
        if (this.maxTotalConnection <= 0) {
            throw new IllegalArgumentException("invalid maxTotalConnection: " + maxTotalConnection);
        }
        if (this.maxConnectionPerRoute <= 0) {
            throw new IllegalArgumentException("invalid maxConnectionPerRoute: " + maxTotalConnection);
        }
        List
   
     headers = new LinkedList<>();
        headers.add(new BasicHeader("Accept-Encoding", "gzip,deflate"));
        headers.add(new BasicHeader("Accept-Language", "zh-CN,zh;q=0.8,en;q=0.6"));
        HttpRequestRetryHandler retryHandler = new DefaultHttpRequestRetryHandler(0, false);
        CloseableHttpClient httpClient = HttpClients.custom()
                .setDefaultHeaders(headers)
                .setRetryHandler(retryHandler)
                .build();
        HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory(httpClient);
        factory.setConnectTimeout(connectionTimeout);
        factory.setReadTimeout(readTimeout);
        return factory;
    }
    private RestTemplate createRestTemplate(ClientHttpRequestFactory factory) {
        RestTemplate restTemplate = new RestTemplate(factory);
        modifyDefaultCharset(restTemplate);
        restTemplate.setErrorHandler(new DefaultResponseErrorHandler());
        return restTemplate;
    }
    private void modifyDefaultCharset(RestTemplate restTemplate) {
        List
    
      converterList = restTemplate.getMessageConverters();
        HttpMessageConverter converterTarget = null;
        for (HttpMessageConverter item : converterList) {
            if (StringHttpMessageConverter.class == item.getClass()) {
                converterTarget = item;
                break;
            }
        }
        if (null != converterTarget) {
            converterList.remove(converterTarget);
        }
        Charset defaultCharset = Charset.forName(charset);
        converterList.add(1, new StringHttpMessageConverter(defaultCharset));
    }
}
    
   

4. Get请求演示

@RestController
public class GetTestController {
    @Resource
    private RestTemplate restTemplate;
    @GetMapping("/baidu1/{key}")
    public String get1(@PathVariable String key) throws UnsupportedEncodingException {
        String encodeKey = URLEncoder.encode(key, "UTF-8");
        String url = "http://www.baidu.com/s?bdorz_come=1&ie=utf-8&f=8&rsv_bp=1&rsv_idx=1&tn=baidu&wd=" + encodeKey;
        return restTemplate.getForObject(url, String.class);
    }
    @GetMapping("/baidu2/{key}")
    public String get2(@PathVariable String key) throws UnsupportedEncodingException {
        HttpHeaders headers = new HttpHeaders();
        headers.set("MyHeaderKey", "MyHeaderValue");
        HttpEntity entity = new HttpEntity(headers);
        String encodeKey = URLEncoder.encode(key, "UTF-8");
        String url = "http://www.baidu.com/s?bdorz_come=1&ie=utf-8&f=8&rsv_bp=1&rsv_idx=1&tn=baidu&wd=" + encodeKey;
        ResponseEntity
   
     response = restTemplate.exchange(url, HttpMethod.GET, entity, String.class);
        return response.getBody();
    }
}
   

5. Post请求演示

@RestController
public class PostTestController {
    @Resource
    private RestTemplate restTemplate;
    @GetMapping("/postForm")
    public String testPostForm() {
        String url = "";
        MultiValueMap
   
     form = new LinkedMultiValueMap<>();
        form.add("name", "**");
        form.add("age", "**");
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
        HttpEntity entity = new HttpEntity(form, headers);
        String json = restTemplate.postForObject(url, entity, String.class);
        return json;
    }
    @RequestMapping("/postBody")
    public String testPostBody() {
        String url = "";
        String jsonBody = "{\n" +
                "    \"name\": \"XX\",\n" +
                "    \"age\": \"12\",\n" +
                "    \"sex\": \"man\"\n" +
                "}\n";
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        HttpEntity entity = new HttpEntity(jsonBody, headers);
        String json = restTemplate.postForObject(url, entity, String.class);
        return json;
        // 如果需要将json转换为Java对象，可以使用restTemplate.postForObject(url, entity, ResultVo.class)
    }
}
   

6. 文件上传与下载请求演示

@RestController
public class FileTestController {
    @Resource
    private RestTemplate restTemplate;
    @RequestMapping("/postFile")
    public String testPostFileBody() {
        String filePath = "D:/config.png";
        String url = "";
        String appId = "";
        String secureKey = "";
        String time = String.valueOf(System.currentTimeMillis());
        String pubStr = "1";
        String tempStr = String.format("app_id=%s&is_public=%s&time=%s&vframe=0%s", appId, pubStr, time, secureKey);
        MultiValueMap
   
     form = new LinkedMultiValueMap<>();
        form.add("is_public", pubStr);
        form.add("vframe", "0");
        form.add("file", new FileSystemResource(new File(filePath)));
        form.add("app_id", appId);
        form.add("time", time);
        form.add("sign", DigestUtils.md5(tempStr));
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        HttpEntity entity = new HttpEntity(form, headers);
        String json = restTemplate.postForObject(url, entity, String.class);
        return json;
    }
    @RequestMapping("/downloadFile")
    public ResponseEntity testDownloadFile() throws Exception {
        String url = "http://editor.baidu.com/editor/download/BaiduEditor(Online)_5-9-16.exe";
        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_OCTET_STREAM));
        HttpEntity entity = new HttpEntity(headers);
        ResponseEntity
    
      response = restTemplate.exchange(url, HttpMethod.GET, entity, byte[].class);
        byte[] bytes = response.getBody();
        long contentLength = bytes != null ? bytes.length : 0;
        headers.setContentLength((int) contentLength);
        headers.setContentDispositionFormData("baidu.exe", URLEncoder.encode("百度安装包.exe", "UTF-8"));
        return new ResponseEntity<>(response.getBody(), headers, HttpStatus.OK);
    }
}
    
   

采坑记录

@Configuration
@ConfigurationProperties(prefix = "spring.restTemplate")
@ConditionalOnClass(value = {RestTemplate.class, CloseableHttpClient.class})
public class RestTemplateConfig {}

@ConfigurationProperties(prefix = "spring.restTemplate")
@ConditionalOnClass(value = {RestTemplate.class, CloseableHttpClient.class})
public class RestTemplateConfig {}

private void modifyDefaultCharset(RestTemplate restTemplate) {
    List
    
      converterList = restTemplate.getMessageConverters();
    HttpMessageConverter converterTarget = null;
    for (HttpMessageConverter item : converterList) {
        if (StringHttpMessageConverter.class == item.getClass()) {
            converterTarget = item;
            break;
        }
    }
    if (null != converterTarget) {
        converterList.remove(converterTarget);
    }
    Charset defaultCharset = Charset.forName(charset);
    converterList.add(1, new StringHttpMessageConverter(defaultCharset));
}
    

@Bean
public RestTemplate getRestTemplate() {
    RestTemplate rest = new RestTemplate(this.createFactory);
    return rest;
}

如何调试RestTemplate

工程目录

[图片描述]

结束语

有任何建议，欢迎留言探讨。