RestTemplate介绍使用,以及整合 HttpClient 连接池配置长连接

浅浅的花香味﹌ 2023-07-09 08:28 25阅读 0赞

# 1、RestTemplate介绍 #

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。

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。

# 2 SpringBoot的restTemplate整合HttpClient连接池及配置 #

## 2.1. 为什么要整合HttpClient ##

RestTemplate是Spring自带的一个调用rest服务的客户端,它提供了多种便捷访问远程Http服务的方法,能够大大提高客户端的编写效率。

RestTemplate默认是使用JDK原生的URLConnection,默认超时为-1, 也就表示是没有超时时间的,这个肯定不能满足复杂情况的使用需求, restTemplate的工厂是支持使用HttpClient和OkHttp来作为客户端实现的

## 2.2. 为什么要使用连接池 ##

在调用rest请求时,每次请求都需要和服务端建立连接,也就是三次握手,这是一个费时费力的工作,如果我们需要频繁对一个服务端进行调用,难道需要一直去建立连接吗?  
     所以使用连接池,可以避免多次建立连接的操作,节省资源开支

## 2.3. 依赖 ##

除了spring的基本依赖以外,还需要准备下面几个依赖:

<dependency>
          <groupId>org.apache.httpcomponents</groupId>
          <artifactId>httpclient</artifactId>
          <version>4.5.7</version>
      </dependency>
    
    
    <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-configuration-processor</artifactId>
         <optional>true</optional>
         <version>${springboot.version}</version>
     </dependency>

## RestTemplate使用 ##

### 直接使用 ###

public class RestTemplateTest {
    	public static void main(String[] args) {
    		RestTemplate restT = new RestTemplate();
    		//通过Jackson JSON processing library直接将返回值绑定到对象
    		Quote quote = restT.getForObject("http://gturnquist-quoters.cfapps.io/api/random", Quote.class);  
    		String quoteString = restT.getForObject("http://gturnquist-quoters.cfapps.io/api/random", String.class);
    		System.out.println(quoteString);
    	}
    }

> Because the Jackson JSON processing library is in the classpath, RestTemplate will use it (via a message converter) to convert the incoming JSON data into a Quote object.

可以看到可以将返回结果放在一个String对象中，也可以直接绑定到一个自定义的对象上，其中Quote如下：

@JsonIgnoreProperties(ignoreUnknown = true) // indicate that any properties not bound in this type should be ignored.
    public class Quote {
    
    	private String type;
        private Value value;
    
        //getters & setters
    }

这里有如下两点需要注意（懒得翻译），@JsonIgnoreProperties如果定义了返回结果中没有的属性则忽略，另外属性名需要和返回结果的属性名一致，否则需要使用@JsonProperty注解进行匹配。

*  It’s annotated with @JsonIgnoreProperties from the Jackson JSON processing library to indicate that any properties not bound in this type should be ignored.
 *  In order for you to directly bind your data to your custom types, you need to specify the variable name exact same as the key in the JSON Document returned from the API. In case your variable name and key in JSON doc are not matching, you need to use @JsonProperty annotation to specify the exact key of JSON document.

### 在Spring boot中使用RestTemplate ###

@SpringBootApplication 
    public class HelloSpringBoot {
    	public static void main(String[] args) {
    	    SpringApplication.run(HelloWorld.class, args);
    	}
    	
    	@Bean
    	public RestTemplate restTemplate(RestTemplateBuilder builder) {
    		return builder.build();
    	}	
    }

注意spring boot并不会自动装配`RestTemplate`类，因为通常用户都需要一个定制的RestTemplate，因此springboot自动装配了一个`RestTemplateBuilder`类方便用户定制创建自己的RestTemplate类。

> Since RestTemplate instances often need to be customized before being used, Spring Boot does not provide any single auto-configured RestTemplate bean. It does, however, auto-configure a RestTemplateBuilder which can be used to create RestTemplate instances when needed. The auto-configured RestTemplateBuilder will ensure that sensible HttpMessageConverters are applied to RestTemplate instances.

`RestTemplateService.java`

@Service
    public class RestTemplateService {
    	@Autowired RestTemplate restTemplate;
    	
    	public Quote someRestCall(){
    		return restTemplate.getForObject("http://gturnquist-quoters.cfapps.io/api/random", Quote.class);
    	}	
    }

`RestTemplateController.java`

@RestController
    @RequestMapping("/api/rest")
    public class RestTemplateController {
    	@Autowired 
    	private RestTemplateService restTemplateService;
    	
    	@RequestMapping
    	public Object index() {
    		return restTemplateService.someRestCall();
    	}
    }

这是访问`http://localhost/api/rest`返回以下结果：

{
    "type": "success",
    "value": {
    	"id": 9,
    	"quote": "So easy it is to switch container in #springboot."
    	}
    }

> `http://gturnquist-quoters.cfapps.io/api/random` is a RESTful service that randomly fetches quotes about Spring Boot and returns them as a JSON document.

## RestTemplate定制 ##

由于不同的rest服务调用可能需要不同的RestTemplate配置，根据适用范围通常有两种方式进行配置。

一、单类定制

`RestTemplateService.java`

@Service
    public class RestTemplateService {
    	private final RestTemplate restTemplate;
    	public RestTemplateService(RestTemplateBuilder builder){  //RestTemplateBuilder will be auto-configured
    		this.restTemplate = builder.setConnectTimeout(1000).setReadTimeout(1000).build();
    	}
    	
    	public Quote someRestCall(){
    		return restTemplate.getForObject("http://gturnquist-quoters.cfapps.io/api/random", Quote.class);
    	}	
    }

# 二、跨类定制 #

`BeanConf.class`

@Configuration
    public class BeanConf {
    
    	@Bean(name = "restTemplateA")
    	public RestTemplate restTemplateA(RestTemplateBuilder builder) {
    		return builder.basicAuthorization("username", "password")  
                .setConnectTimeout(3000)  
                .setReadTimeout(5000)  
                .rootUri("http://api1.example.com/")  
                .errorHandler(new CustomResponseErrorHandler())  
                .additionalMessageConverters(new CustomHttpMessageConverter())  
                .uriTemplateHandler(new OkHttp3ClientHttpRequestFactory())  
                .build();
    	}
    	
    	@Bean(name = "restTemplateB")
    	public RestTemplate restTemplateB(RestTemplateBuilder builder) {
    		return builder.basicAuthorization("username", "password")  
                .setConnectTimeout(1000)  
                .setReadTimeout(1000)  
                .rootUri("http://api2.example.com/")  
                .errorHandler(new CustomResponseErrorHandler())  
                .additionalMessageConverters(new CustomHttpMessageConverter())  
                .uriTemplateHandler(new OkHttp3ClientHttpRequestFactory())  
                .build();
    	}
    }

`RestTemplateService.java`

@Service
    public class RestTemplateService {
    	@Resource(name = "restTemplateB")
    	private RestTemplate restTemplate;
    	
    	public Quote someRestCall(){
    		return restTemplate.getForObject("http://gturnquist-quoters.cfapps.io/api/random", Quote.class);
    	}
    }

# 三、应用内定制 #

通过实现`RestTemplateCustomizer`接口，其中的设置在所有通过`RestTemplateBuilder`创建的RestTemplate都将生效。

@Component  
    public class CustomRestTemplateCustomizer implements RestTemplateCustomizer {  
        @Override  
        public void customize(RestTemplate restTemplate) {  
            new RestTemplateBuilder()  
                    .detectRequestFactory(false)  
                    .basicAuthorization("username", "password")  
                    .uriTemplateHandler(new OkHttp3ClientHttpRequestFactory())  
                    .errorHandler(new CustomResponseErrorHandler())  
                    .configure(restTemplate);  
        }  
    }

## http连接池 ##

> By default RestTemplate creates new Httpconnection every time and closes the connection once done.If you need to have a connection pooling under rest template then you may use different implementation of the ClientHttpRequestFactory that pools the connections.

RestTemplate默认不使用连接池，如果想使用则需要一个`ClientHttpRequestFactory`接口的实现类来池化连接。例如使用`HttpComponentsClientHttpRequestFactory`。

RestTemplate restT = new RestTemplate(new HttpComponentsClientHttpRequestFactory());

注意`HttpComponentsClientHttpRequestFactory` 是 `org.springframework.http.client.ClientHttpRequestFactory`的实现类，它底层使用了[Apache HttpComponents HttpClient][] to create requests.

## References ##

*  [spring-boot docs Calling REST services][]
 *  [an application that uses Spring’s RestTemplate to retrieve a random Spring Boot quotation][an application that uses Spring_s RestTemplate to retrieve a random Spring Boot quotation]
 *  [Consuming a RESTful Web Service][]

# 自定义例子： #

## 例子1： ##

配置类

package com.zgd.springboot.demo.template.config;
    
    import com.alibaba.fastjson.JSON;
    import lombok.Data;
    import lombok.extern.slf4j.Slf4j;
    import org.apache.http.Header;
    import org.apache.http.HeaderElement;
    import org.apache.http.HeaderElementIterator;
    import org.apache.http.HttpHost;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.protocol.HttpClientContext;
    import org.apache.http.config.Registry;
    import org.apache.http.config.RegistryBuilder;
    import org.apache.http.conn.ConnectionKeepAliveStrategy;
    import org.apache.http.conn.socket.ConnectionSocketFactory;
    import org.apache.http.conn.socket.PlainConnectionSocketFactory;
    import org.apache.http.conn.ssl.NoopHostnameVerifier;
    import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.DefaultHttpRequestRetryHandler;
    import org.apache.http.impl.client.HttpClientBuilder;
    import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
    import org.apache.http.message.BasicHeader;
    import org.apache.http.message.BasicHeaderElementIterator;
    import org.apache.http.protocol.HTTP;
    import org.apache.http.ssl.SSLContextBuilder;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.http.client.ClientHttpRequestFactory;
    import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
    import org.springframework.http.converter.HttpMessageConverter;
    import org.springframework.http.converter.StringHttpMessageConverter;
    import org.springframework.stereotype.Component;
    import org.springframework.web.client.DefaultResponseErrorHandler;
    import org.springframework.web.client.RestTemplate;
    
    import javax.net.ssl.HostnameVerifier;
    import javax.net.ssl.SSLContext;
    import java.nio.charset.Charset;
    import java.security.KeyManagementException;
    import java.security.KeyStoreException;
    import java.security.NoSuchAlgorithmException;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import java.util.Optional;
    
    /**
     * @Author: zgd
     * @Date: 2019/3/25 16:53
     * @Description:
     */
    @Configuration
    @Component
    @ConditionalOnClass(value = {RestTemplate.class, CloseableHttpClient.class})
    @Data
    @Slf4j
    public class HttpClientConfig {
    
      @Autowired
      private HttpClientPoolConfig httpClientPoolConfig;
    
      @Bean
      public RestTemplate restTemplate() {
        return new RestTemplate();
      }
    
    
      /**
       * 创建HTTP客户端工厂
       */
      @Bean(name = "clientHttpRequestFactory")
      public ClientHttpRequestFactory clientHttpRequestFactory() {
        /**
         *  maxTotalConnection 和 maxConnectionPerRoute 必须要配
         */
        if (httpClientPoolConfig.getMaxTotalConnect() <= 0) {
          throw new IllegalArgumentException("invalid maxTotalConnection: " + httpClientPoolConfig.getMaxTotalConnect());
        }
        if (httpClientPoolConfig.getMaxConnectPerRoute() <= 0) {
          throw new IllegalArgumentException("invalid maxConnectionPerRoute: " + httpClientPoolConfig.getMaxConnectPerRoute());
        }
        HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(httpClient());
        // 连接超时
        clientHttpRequestFactory.setConnectTimeout(httpClientPoolConfig.getConnectTimeout());
        // 数据读取超时时间，即SocketTimeout
        clientHttpRequestFactory.setReadTimeout(httpClientPoolConfig.getReadTimeout());
        // 从连接池获取请求连接的超时时间，不宜过长，必须设置，比如连接不够用时，时间过长将是灾难性的
        clientHttpRequestFactory.setConnectionRequestTimeout(httpClientPoolConfig.getConnectionRequestTimout());
        return clientHttpRequestFactory;
      }
    
      /**
       * 初始化RestTemplate,并加入spring的Bean工厂，由spring统一管理
       */
      @Bean(name = "httpClientTemplate")
      public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        return createRestTemplate(factory);
      }
    
      /**
       * 初始化支持异步的RestTemplate,并加入spring的Bean工厂，由spring统一管理,如果你用不到异步，则无须创建该对象
       * 这个类过时了
       * @return
       */
    /*  @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);
      }*/
    
      /**
       * 配置httpClient
       *
       * @return
       */
      @Bean
      public HttpClient httpClient() {
        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
        try {
          //设置信任ssl访问
          SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, (arg0, arg1) -> true).build();
    
          httpClientBuilder.setSSLContext(sslContext);
          HostnameVerifier hostnameVerifier = NoopHostnameVerifier.INSTANCE;
          SSLConnectionSocketFactory sslConnectionSocketFactory = new SSLConnectionSocketFactory(sslContext, hostnameVerifier);
          Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create()
                  // 注册http和https请求
                  .register("http", PlainConnectionSocketFactory.getSocketFactory())
                  .register("https", sslConnectionSocketFactory).build();
    
          //使用Httpclient连接池的方式配置(推荐)，同时支持netty，okHttp以及其他http框架
          PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
          // 最大连接数
          poolingHttpClientConnectionManager.setMaxTotal(httpClientPoolConfig.getMaxTotalConnect());
          // 同路由并发数
          poolingHttpClientConnectionManager.setDefaultMaxPerRoute(httpClientPoolConfig.getMaxConnectPerRoute());
          //配置连接池
          httpClientBuilder.setConnectionManager(poolingHttpClientConnectionManager);
          // 重试次数
          httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(httpClientPoolConfig.getRetryTimes(), true));
    
          //设置默认请求头
          List<Header> headers = getDefaultHeaders();
          httpClientBuilder.setDefaultHeaders(headers);
          //设置长连接保持策略
          httpClientBuilder.setKeepAliveStrategy(connectionKeepAliveStrategy());
          return httpClientBuilder.build();
        } catch (KeyManagementException | NoSuchAlgorithmException | KeyStoreException e) {
          log.error("初始化HTTP连接池出错", e);
        }
        return null;
      }
    
    
      /**
       * 配置长连接保持策略
       * @return
       */
      public ConnectionKeepAliveStrategy connectionKeepAliveStrategy(){
        return (response, context) -> {
          // Honor 'keep-alive' header
          HeaderElementIterator it = new BasicHeaderElementIterator(
                  response.headerIterator(HTTP.CONN_KEEP_ALIVE));
          while (it.hasNext()) {
            HeaderElement he = it.nextElement();
            log.info("HeaderElement:{}", JSON.toJSONString(he));
            String param = he.getName();
            String value = he.getValue();
            if (value != null && "timeout".equalsIgnoreCase(param)) {
              try {
                return Long.parseLong(value) * 1000;
              } catch(NumberFormatException ignore) {
                log.error("解析长连接过期时间异常",ignore);
              }
            }
          }
          HttpHost target = (HttpHost) context.getAttribute(
                  HttpClientContext.HTTP_TARGET_HOST);
          //如果请求目标地址,单独配置了长连接保持时间,使用该配置
          Optional<Map.Entry<String, Integer>> any = Optional.ofNullable(httpClientPoolProperties.getKeepAliveTargetHost()).orElseGet(HashMap::new)
                  .entrySet().stream().filter(
                  e -> e.getKey().equalsIgnoreCase(target.getHostName())).findAny();
          //否则使用默认长连接保持时间
          return any.map(en -> en.getValue() * 1000L).orElse(httpClientPoolProperties.getKeepAliveTime() * 1000L);
        };
      }
    
    
      /**
       * 设置请求头
       *
       * @return
       */
      private List<Header> getDefaultHeaders() {
        List<Header> headers = new ArrayList<>();
        headers.add(new BasicHeader("User-Agent",
                "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.16 Safari/537.36"));
        headers.add(new BasicHeader("Accept-Encoding", "gzip,deflate"));
        headers.add(new BasicHeader("Accept-Language", "zh-CN"));
        headers.add(new BasicHeader("Connection", "Keep-Alive"));
        return headers;
      }
    
    
      private RestTemplate createRestTemplate(ClientHttpRequestFactory factory) {
        RestTemplate restTemplate = new RestTemplate(factory);
    
        //我们采用RestTemplate内部的MessageConverter
        //重新设置StringHttpMessageConverter字符集，解决中文乱码问题
        modifyDefaultCharset(restTemplate);
    
        //设置错误处理器
        restTemplate.setErrorHandler(new DefaultResponseErrorHandler());
    
        return restTemplate;
      }
    
      /**
       * 修改默认的字符集类型为utf-8
       *
       * @param restTemplate
       */
      private void modifyDefaultCharset(RestTemplate restTemplate) {
        List<HttpMessageConverter<?>> 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(httpClientPoolConfig.getCharset());
        converterList.add(1, new StringHttpMessageConverter(defaultCharset));
      }
    }

这里有个注意点,就是RestTemplate的bean命名,建议和restTemplate区分开, 这样我们如果需要原生的restTemplate,就用restTemplate,如果用我们自定义的,就用httpClientTemplate

@Resource
    private RestTemplate restTemplate;
    
    @Resource
    private RestTemplate httpClientTemplate;

连接池的配置类:  
这里如果没有上面的spring-boot-configuration-processor这个依赖,会报错

package com.zgd.springboot.demo.template.config;
    
    import lombok.Data;
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.stereotype.Component;
    
    import java.util.Map;
    
    /**
     * @Author: zgd
     * @Date: 2019/3/26 19:00
     * @Description:
     */
    @Component
    @ConfigurationProperties(prefix = "spring.http-client.pool")
    @Data
    public class HttpClientPoolConfig {
    
      /**
       * 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
       */
      /**
       * 连接池的最大连接数
       */
      private int maxTotalConnect ;
      /**
       * 同路由的并发数
       */
      private int maxConnectPerRoute ;
      /**
       * 客户端和服务器建立连接超时，默认2s
       */
      private int connectTimeout = 2 * 1000;
      /**
       * 指客户端从服务器读取数据包的间隔超时时间,不是总读取时间，默认30s
       */
      private int readTimeout = 30 * 1000;
    
      private String charset = "UTF-8";
      /**
       * 重试次数,默认2次
       */
      private int retryTimes = 2;
      /**
       * 从连接池获取连接的超时时间,不宜过长,单位ms
       */
      private int connectionRequestTimout = 200;
      /**
       * 针对不同的地址,特别设置不同的长连接保持时间
       */
      private Map<String,Integer> keepAliveTargetHost;
      /**
       * 针对不同的地址,特别设置不同的长连接保持时间,单位 s
       */
      private int keepAliveTime = 60;
    
    }

application.yml:

spring:
      # 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
      http-client:
        pool:
          #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
          maxTotalConnect: 1000
          #每个路由的最大连接数,如果只调用一个地址,可以将其设置为最大连接数
          maxConnectPerRoute: 200
          # 指客户端和服务器建立连接的超时时间,ms , 最大约21秒,因为内部tcp在进行三次握手建立连接时,默认tcp超时时间是20秒
          connectTimeout: 3000
          # 指客户端从服务器读取数据包的间隔超时时间,不是总读取时间,也就是socket timeout,ms
          readTimeout: 5000
          # 从连接池获取连接的timeout,不宜过大,ms
          connectionRequestTimout: 200
          # 重试次数
          retryTimes: 3
          charset: UTF-8
          # 长连接保持时间 单位s,不宜过长
          keepAliveTime: 10
          # 针对不同的网址,长连接保持的存活时间,单位s,如果是频繁而持续的请求,可以设置小一点,不建议设置过大,避免大量无用连接占用内存资源
          keepAliveTargetHost:
            www.baidu.com: 5

maxTotalConnect: 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: 每个路由的最大连接数,如果只调用同一个服务端,可以设置和最大连接数相同,也就是一个路由  
connectTimeout: 客户端和服务端建立连接的超时时间,这里最大只能是21s,因为操作系统的tcp进行三次握手时,有它自己的超时时间,即便设置100s也是在21s后报错.  
readTimeout: 也就是socketTime,指的是两个相邻的数据包的间隔超时时间,比如下载一个比较大的文件,就算耗时很长也不会中断,但是如果两次响应时间间隔超过这个值就会报错.  
举个例子:  
将这个时间设置为2000ms, 然后分别去请求这两个接口,这两个接口总的等待时间都是3000ms

@GetMapping("/sleep")
      public String sleep(@RequestParam(required = false,defaultValue = "3000") Integer mils) {
        log.info("sleep:{}",mils);
        try {
          TimeUnit.MILLISECONDS.sleep(mils);
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
        return "hello!" + mils;
      }
    
    
      @GetMapping("/sleep/on_and_off")
      public void sleepOnAndOff(HttpServletResponse response) {
        log.info("sleepOnAndOff");
        for (int i = 0;i < 10;i++){
          try {
            response.getWriter().println("" + i);
            response.flushBuffer();
            Thread.sleep(300);
          } catch (Exception e) {
            e.printStackTrace();
          }
        }
      }

参考：

[Using RestTemplate · jiwenxing/spring-boot-demo Wiki · GitHub][Using RestTemplate _ jiwenxing_spring-boot-demo Wiki _ GitHub]

[SpringBoot的restTemplate整合HttpClient连接池及配置\_zzzgd\_666的博客-CSDN博客\_resttemplate 连接池][SpringBoot_restTemplate_HttpClient_zzzgd_666_-CSDN_resttemplate]

[springboot 2.0 整合 RestTemplate 与使用教程\_李虹柏的博客-CSDN博客][springboot 2.0 _ RestTemplate _-CSDN]

[springboot学习记录之RestTemplate - 简书][springboot_RestTemplate -]

[SpringBoot RestTemplate 整合 HttpClient 连接池 配置长连接-java黑洞网][SpringBoot RestTemplate _ HttpClient _ _-java]

[RestTemplate Httpclient连接池 - 简书][RestTemplate Httpclient_ -]

[Apache HttpComponents HttpClient]: http://hc.apache.org/httpcomponents-client-ga/
[spring-boot docs Calling REST services]: https://docs.spring.io/spring-boot/docs/1.5.4.RELEASE/reference/htmlsingle/#boot-features-restclient
[an application that uses Spring_s RestTemplate to retrieve a random Spring Boot quotation]: https://github.com/spring-guides/gs-consuming-rest
[Consuming a RESTful Web Service]: https://spring.io/guides/gs/consuming-rest/
[Using RestTemplate _ jiwenxing_spring-boot-demo Wiki _ GitHub]: https://github.com/jiwenxing/spring-boot-demo/wiki/Using-RestTemplate
[SpringBoot_restTemplate_HttpClient_zzzgd_666_-CSDN_resttemplate]: https://blog.csdn.net/zzzgd_666/article/details/88858181
[springboot 2.0 _ RestTemplate _-CSDN]: https://blog.csdn.net/weixin_40461281/article/details/83540604
[springboot_RestTemplate -]: https://www.jianshu.com/p/88b77d011c8a
[SpringBoot RestTemplate _ HttpClient _ _-java]: http://www.javaheidong.com/blog/article/137151/581364ae5b7d556e707e/
[RestTemplate Httpclient_ -]: https://www.jianshu.com/p/50de52fb9e8e