RestTemplate使用详解

今天药忘吃喽~ 2022-12-07 11:46 270阅读 0赞

> ## **`                 RestTemplate使用详解`** ##
> 
> `RestTemplate`是`Spring`提供的用于访问Rest服务的客户端，`RestTemplate`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。

我之前的HTTP开发是用apache的HttpClient开发，代码复杂，还得操心资源回收等。代码很复杂，冗余代码多，稍微截个图，这是我封装好的一个post请求工具：

![format_png][]

本教程将带领大家实现Spring生态内RestTemplate的`Get请求`和`Post请求`还有`exchange指定请求类型`的实践和`RestTemplate`核心方法源码的分析，看完你就会用优雅的方式来发HTTP请求。

### 1. 简述RestTemplate ###

> 是`Spring`用于同步client端的核心类，简化了与`http`服务的通信，并满足`RestFul`原则，程序代码可以给它提供URL，并提取结果。默认情况下，`RestTemplate`默认依赖jdk的HTTP连接工具。当然你也可以 通过`setRequestFactory`属性切换到不同的HTTP源，比如`Apache HttpComponents`、`Netty`和`OkHttp`。

RestTemplate能大幅简化了提交表单数据的难度，并且附带了自动转换JSON数据的功能，但只有理解了HttpEntity的组成结构（header与body），且理解了与uriVariables之间的差异，才能真正掌握其用法。这一点在Post请求更加突出，下面会介绍到。

该类的入口主要是根据HTTP的六个方法制定：

<table> 
 <thead> 
  <tr> 
   <th>HTTP method</th> 
   <th>RestTemplate methods</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>DELETE</td> 
   <td>delete</td> 
  </tr> 
  <tr> 
   <td>GET</td> 
   <td>getForObject</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>getForEntity</td> 
  </tr> 
  <tr> 
   <td>HEAD</td> 
   <td>headForHeaders</td> 
  </tr> 
  <tr> 
   <td>OPTIONS</td> 
   <td>optionsForAllow</td> 
  </tr> 
  <tr> 
   <td>POST</td> 
   <td>postForLocation</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>postForObject</td> 
  </tr> 
  <tr> 
   <td>PUT</td> 
   <td>put</td> 
  </tr> 
  <tr> 
   <td>any</td> 
   <td>exchange</td> 
  </tr> 
  <tr> 
   <td>&nbsp;</td> 
   <td>execute</td> 
  </tr> 
 </tbody> 
</table>

此外，exchange和excute可以通用上述方法。

在内部，`RestTemplate`默认使用`HttpMessageConverter`实例将`HTTP`消息转换成`POJO`或者从`POJO`转换成`HTTP`消息。默认情况下会注册主mime类型的转换器，但也可以通过`setMessageConverters`注册其他的转换器。(其实这点在使用的时候是察觉不到的，很多方法有一个responseType 参数，它让你传入一个响应体所映射成的对象，然后底层用HttpMessageConverter将其做映射)

HttpMessageConverterExtractor<T> responseExtractor =
                    new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);

`HttpMessageConverter.java`源码：

public interface HttpMessageConverter<T> {
            //指示此转换器是否可以读取给定的类。
        boolean canRead(Class<?> clazz, @Nullable MediaType mediaType);
    
            //指示此转换器是否可以写给定的类。
        boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType);
    
            //返回List<MediaType>
        List<MediaType> getSupportedMediaTypes();
    
            //读取一个inputMessage
        T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
                throws IOException, HttpMessageNotReadableException;
    
            //往output message写一个Object
        void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
                throws IOException, HttpMessageNotWritableException;
    
    }

在内部，`RestTemplate`默认使用`SimpleClientHttpRequestFactory`和`DefaultResponseErrorHandler`来分别处理`HTTP`的创建和错误，但也可以通过`setRequestFactory`和`setErrorHandler`来覆盖。

### 2. get请求实践 ###

2.1. getForObject()方法

public <T> T getForObject(String url, Class<T> responseType, Object... uriVariables){}
    public <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables)
    public <T> T getForObject(URI url, Class<T> responseType)

`getForObject()`其实比`getForEntity()`多包含了将HTTP转成POJO的功能，但是`getForObject`没有处理`response`的能力。因为它拿到手的就是成型的`pojo`。省略了很多`response`的信息。

2.1.1 POJO:

public class Notice {
        private int status;
        private Object msg;
        private List<DataBean> data;
    }
    public  class DataBean {
      private int noticeId;
      private String noticeTitle;
      private Object noticeImg;
      private long noticeCreateTime;
      private long noticeUpdateTime;
      private String noticeContent;
    }

示例：2.1.2 不带参的get请求

/**
         * 不带参的get请求
         */
        @Test
        public void restTemplateGetTest(){
            RestTemplate restTemplate = new RestTemplate();
            Notice notice = restTemplate.getForObject("http://xxx.top/notice/list/1/5"
                    , Notice.class);
            System.out.println(notice);
        }

控制台打印：

INFO 19076 --- [           main] c.w.s.c.w.c.HelloControllerTest          
    : Started HelloControllerTest in 5.532 seconds (JVM running for 7.233)
    
    Notice{status=200, msg=null, data=[DataBean{noticeId=21, noticeTitle='aaa', noticeImg=null, 
    noticeCreateTime=1525292723000, noticeUpdateTime=1525292723000, noticeContent='<p>aaa</p>'}, 
    DataBean{noticeId=20, noticeTitle='ahaha', noticeImg=null, noticeCreateTime=1525291492000, 
    noticeUpdateTime=1525291492000, noticeContent='<p>ah.......'

示例：2.1.3 带参数的get请求1

Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/{1}/{2}"
                    , Notice.class,1,5);

明眼人一眼能看出是用了占位符`{1}`。

示例：2.1.4 带参数的get请求2

Map<String,String> map = new HashMap();
            map.put("start","1");
            map.put("page","5");
            Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/"
                    , Notice.class,map);

明眼人一看就是利用map装载参数，不过它默认解析的是`PathVariable`的url形式。

2.2 getForEntity()方法

public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables){}
    public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables){}
    public <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType){}

与getForObject()方法不同的是返回的是`ResponseEntity`对象，如果需要转换成pojo，还需要json工具类的引入，这个按个人喜好用。不会解析json的可以百度`FastJson`或者`Jackson`等工具类。然后我们就研究一下`ResponseEntity`下面有啥方法。

ResponseEntity、HttpStatus、BodyBuilder结构

ResponseEntity.java

public HttpStatus getStatusCode(){}
    public int getStatusCodeValue(){}
    public boolean equals(@Nullable Object other) {}
    public String toString() {}
    public static BodyBuilder status(HttpStatus status) {}
    public static BodyBuilder ok() {}
    public static <T> ResponseEntity<T> ok(T body) {}
    public static BodyBuilder created(URI location) {}
    ...

HttpStatus.java

public enum HttpStatus {
    public boolean is1xxInformational() {}
    public boolean is2xxSuccessful() {}
    public boolean is3xxRedirection() {}
    public boolean is4xxClientError() {}
    public boolean is5xxServerError() {}
    public boolean isError() {}
    }

BodyBuilder.java

public interface BodyBuilder extends HeadersBuilder<BodyBuilder> {
        //设置正文的长度，以字节为单位，由Content-Length标头
          BodyBuilder contentLength(long contentLength);
        //设置body的MediaType 类型
          BodyBuilder contentType(MediaType contentType);
        //设置响应实体的主体并返回它。
          <T> ResponseEntity<T> body(@Nullable T body);
    ｝

可以看出来，ResponseEntity包含了HttpStatus和BodyBuilder的这些信息，这更方便我们处理response原生的东西。

示例：

@Test
    public void rtGetEntity(){
            RestTemplate restTemplate = new RestTemplate();
            ResponseEntity<Notice> entity = restTemplate.getForEntity("http://fantj.top/notice/list/1/5"
                    , Notice.class);
    
            HttpStatus statusCode = entity.getStatusCode();
            System.out.println("statusCode.is2xxSuccessful()"+statusCode.is2xxSuccessful());
    
            Notice body = entity.getBody();
            System.out.println("entity.getBody()"+body);
    
    
            ResponseEntity.BodyBuilder status = ResponseEntity.status(statusCode);
            status.contentLength(100);
            status.body("我在这里添加一句话");
            ResponseEntity<Class<Notice>> body1 = status.body(Notice.class);
            Class<Notice> body2 = body1.getBody();
            System.out.println("body1.toString()"+body1.toString());
        }

statusCode.is2xxSuccessful()true
    entity.getBody()Notice{status=200, msg=null, data=[DataBean{noticeId=21, noticeTitle='aaa', ...
    body1.toString()<200 OK,class com.waylau.spring.cloud.weather.pojo.Notice,{Content-Length=[100]}>

当然，还有`getHeaders()`等方法没有举例。

### 3. post请求实践 ###

> 同样的,post请求也有`postForObject`和`postForEntity`。

public <T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Object... uriVariables)
                throws RestClientException {}
    public <T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Map<String, ?> uriVariables)
                throws RestClientException {}
    public <T> T postForObject(URI url, @Nullable Object request, Class<T> responseType) throws RestClientException {}

示例

> 我用一个验证邮箱的接口来测试。

@Test
    public void rtPostObject(){
        RestTemplate restTemplate = new RestTemplate();
        String url = "http://47.xxx.xxx.96/register/checkEmail";
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
        MultiValueMap<String, String> map= new LinkedMultiValueMap<>();
        map.add("email", "844072586@qq.com");
    
        HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);
        ResponseEntity<String> response = restTemplate.postForEntity( url, request , String.class );
        System.out.println(response.getBody());
    }

执行结果：

{"status":500,"msg":"该邮箱已被注册","data":null}

![format_png 1][]

代码中，`MultiValueMap`是`Map`的一个子类，它的一个`key`可以存储多个`value`，简单的看下这个接口：

public interface MultiValueMap<K, V> extends Map<K, List<V>> {...}

为什么用`MultiValueMap`?因为`HttpEntity`接受的request类型是它。

public HttpEntity(@Nullable T body, @Nullable MultiValueMap<String, String> headers){}
    我这里只展示它的一个construct,从它可以看到我们传入的map是请求体，headers是请求头。

为什么用`HttpEntity`是因为`restTemplate.postForEntity`方法虽然表面上接收的request是`@Nullable Object request`类型，但是你追踪下去会发现，这个`request`是用`HttpEntity`来解析。核心代码如下：

if (requestBody instanceof HttpEntity) {
        this.requestEntity = (HttpEntity<?>) requestBody;
    }else if (requestBody != null) {
        this.requestEntity = new HttpEntity<>(requestBody);
    }else {
        this.requestEntity = HttpEntity.EMPTY;
    }

我曾尝试用map来传递参数，编译不会报错，但是执行不了，是无效的url request请求(400 ERROR)。其实这样的请求方式已经满足post请求了，cookie也是属于header的一部分。可以按需求设置请求头和请求体。其它方法与之类似。

### 4. 使用exchange指定调用方式 ###

> exchange()方法跟上面的getForObject()、getForEntity()、postForObject()、postForEntity()等方法不同之处在于它可以指定请求的HTTP类型。

![format_png 2][]

但是你会发现exchange的方法中似乎都有`@Nullable HttpEntity<?> requestEntity`这个参数，这就意味着我们至少要用HttpEntity来传递这个请求体，之前说过源码所以建议就使用HttpEntity提高性能。

示例

@Test
        public void rtExchangeTest() throws JSONException {
            RestTemplate restTemplate = new RestTemplate();
            String url = "http://xxx.top/notice/list";
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
            JSONObject jsonObj = new JSONObject();
            jsonObj.put("start",1);
            jsonObj.put("page",5);
    
            HttpEntity<String> entity = new HttpEntity<>(jsonObj.toString(), headers);
            ResponseEntity<JSONObject> exchange = restTemplate.exchange(url, 
                                              HttpMethod.GET, entity, JSONObject.class);
            System.out.println(exchange.getBody());
        }

这次可以看到，我使用了`JSONObject`对象传入和返回。

当然，HttpMethod方法还有很多，用法类似。

### 5. excute()指定调用方式 ###

`excute()`的用法与`exchange()`大同小异了，它同样可以指定不同的`HttpMethod`，不同的是它返回的对象是响应体所映射成的对象`<T>`，而不是`ResponseEntity<T>`。

需要强调的是，`execute()`方法是以上所有方法的底层调用。随便看一个：

@Override
        @Nullable
        public <T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Map<String, ?> uriVariables)
                throws RestClientException {
    
            RequestCallback requestCallback = httpEntityCallback(request, responseType);
            HttpMessageConverterExtractor<T> responseExtractor =
                    new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
            return execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables);
        }

在项目中，当我们需要远程调用一个HTTP接口时，我们经常会用到RestTemplate这个类。这个类是Spring框架提供的一个工具类。Spring官网对它的介绍如下：

> [`RestTemplate`][RestTemplate]: The original Spring REST client with a synchronous, template method API.

从上面的介绍中我们可以知道：RestTemplate是一个同步的Rest API客户端。下面我们就来介绍下RestTemplate的常用功能。

### RestTemplate简单使用[\#][Link 1] ###

RestTemplate提供高度封装的接口，可以让我们非常方便地进行Rest API调用。常见的方法如下：

表格：RestTemplate的方法

[![format_png 3][]][format_png 3 1]

上面的方法我们大致可以分为三组：

*  getForObject --- optionsForAllow分为一组，这类方法是常规的Rest API（GET、POST、DELETE等）方法调用；
 *  exchange：接收一个`RequestEntity` 参数，可以自己设置HTTP method, URL, headers和body。返回ResponseEntity。
 *  execute：通过callback 接口，可以对请求和返回做更加全面的自定义控制。

一般情况下，我们使用第一组和第二组方法就够了。

创建RestTemplate[\#][Link 2]

@Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        RestTemplate restTemplate = new RestTemplate(factory);
        return restTemplate;
    }
    
    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setReadTimeout(5000);
        factory.setConnectTimeout(15000);
        //设置代理
        //factory.setProxy(null);
        return factory;
    }

创建RestTemplate时需要一个ClientHttpRequestFactory，通过这个请求工厂，我们可以统一设置请求的超时时间，设置代理以及一些其他细节。通过上面代码配置后，我们直接在代码中注入RestTemplate就可以使用了。

接口调用[\#][Link 3]

**1. 普通接口调用**

Map<String, String> vars = Collections.singletonMap("hotel", "42");
    //通过GET方式调用，返回一个String值，还可以给URL变量设置值（也可通过uriTemplateHandler这个属性自定义）
    String result = restTemplate.getForObject(
            "https://example.com/hotels/{hotel}/rooms/{hotel}", String.class, vars);
    
    String url = "http://127.0.0.1:8080/hello";
    JSONObject param = new JSONObject();
    //restTemplate会根据params的具体类型，调用合适的HttpMessageConvert将请求参数写到请求体body中，并在请求头中添加合适的content-type；
    //也会根据responseType的类型（本列子中是JSONObject），设置head中的accept字段，当响应返回的时候再调用合适的HttpMessageConvert进行响应转换
    ResponseEntity<JSONObject> responseEntity=restTemplate.postForEntity(url,params,JSONObject.class);
    int statusCodeValue = responseEntity.getStatusCodeValue();
    HttpHeaders headers = responseEntity.getHeaders();
    JSONObject body = responseEntity.getBody();

**2. 添加Header和Cookie**

有时候，我们需要在请求中的Head中添加值或者将某些值通过cookie传给服务端，那么上面这种调用形式就不太满足要求了。

UriComponents uriComponents = UriComponentsBuilder.fromHttpUrl("127.0.0.1:8080").
                    path("/test").build(true);
     URI uri = uriComponents.toUri();
     
    RequestEntity<JSONObject> requestEntity = RequestEntity.post(uri).
                    //添加cookie(这边有个问题，假如我们要设置cookie的生命周期，作用域等参数我们要怎么操作)
                    header(HttpHeaders.COOKIE,"key1=value1").
                    //添加header
                    header(("MyRequestHeader", "MyValue")
                    accept(MediaType.APPLICATION_JSON).
                    contentType(MediaType.APPLICATION_JSON).
                    body(requestParam);
    ResponseEntity<JSONObject> responseEntity = restTemplate.exchange(requestEntity,JSONObject.class);
    //响应结果
    JSONObject responseEntityBody = responseEntity.getBody();

**3. 文件上传**

上面两个列子基本能覆盖我们平时开发的大多数功能了。这边再讲个文件上传的列子（RestTemplate功能还是蛮全的）。

public Object uplaod(@RequestBody JSONObject params) throws Exception{
    
            final String url = "http://localhost:8888/hello/m3";
            //设置请求头
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.MULTIPART_FORM_DATA);
            //设置请求体，注意是LinkedMultiValueMap
            FileSystemResource resource1 = new FileSystemResource("D:\\dir1\\ss\\pic1.jpg");
            FileSystemResource resource2 = new FileSystemResource("D:\\dir1\\ss\\pic2.jpg");
           
            MultiValueMap<String, Object> form = new LinkedMultiValueMap<>();
            form.add("file", resource1);
            form.add("file", resource2);
            form.add("param1","value1");
    
            HttpEntity<MultiValueMap<String, Object>> files = new HttpEntity<>(form, headers);
            JSONObject s = restTemplate.postForObject(url, files, JSONObject.class);
            return s;
        }

上面的代码中上传了两个本地图片，通过下面代码可以顺利接收。

@RequestMapping("/m3")
    public Object fileUpload(@RequestParam("file") MultipartFile[] files, HttpServletRequest request) throws Exception {
        //携带的其他参数可以使用getParameter方法接收
        String param1 = request.getParameter("param1");
        Response response = new Response();
        if (files == null) {
            response.failure("文件上传错误,服务端未拿到上传的文件！");
            return response;
        }
        for (MultipartFile file : files) {
            if (!file.isEmpty() && file.getSize() > 0) {
                String fileName = file.getOriginalFilename();
                //参考FileCopyUtils这个工具类
                file.transferTo(new File("D:\\" + fileName));
                logger.info("文件:{} 上传成功...",fileName);
            }
        }
        response.success("文件上传成功");
        return response;
        }

但是我们发现上面的上传代码中，上传文件的类必须使用FileSystemResource。有时我们会碰到这种情况：文件我们会从文件服务下载到内存中一个InputStream的形式存在，那此时在使用FileSystemResource就不行了。

当然，我们使用讨巧一点的办法也是可以的：先将下载下来的InputStream保存到本地，然后再读取到FileSystemResource，上传后再删除本地临时文件。

但是总觉得这个方法不够完美。最后发现有个同事已经写了相关的实现。这边就直接拿来用了。

//自己实现了一个Resource
    public class InMemoryResource extends ByteArrayResource {
        private final String filename;
        private final long lastModified;
    
        public InMemoryResource(String filename, String description, byte[] content, long lastModified) {
            super(content, description);
            this.lastModified = lastModified;
            this.filename = filename;
        }
        
        @Override
        public long lastModified() throws IOException {
            return this.lastModified;
        }
    
        @Override
        public String getFilename() {
            return this.filename;
        }
    }

调整后的上传代码

@PostMapping("/m3")
        public Object m3(@RequestBody JSONObject params) throws Exception{
    
            final String url = "http://localhost:8888/hello/m3";
            //设置请求头
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.MULTIPART_FORM_DATA);
            //设置请求体，注意是LinkedMultiValueMap
            //下面两个流从文件服务下载，这边省略（注意最后关闭流）
            InputStream fis1 = 
            InputStream fis2 = 
    
            InMemoryResource resource1 = new InMemoryResource("file1.jpg","description1", FileCopyUtils.copyToByteArray(fis1), System.currentTimeMillis());
            InMemoryResource resource2 = new InMemoryResource("file2.jpg","description2", FileCopyUtils.copyToByteArray(fis2), System.currentTimeMillis());
            MultiValueMap<String, Object> form = new LinkedMultiValueMap<>();
            form.add("file", resource1);
            form.add("file", resource2);
            form.add("param1","value1");
    
            HttpEntity<MultiValueMap<String, Object>> files = new HttpEntity<>(form, headers);
            JSONObject s = restTemplate.postForObject(url, files, JSONObject.class);
            return s;
        }

### 一些其他设置[\#][Link 4] ###

**1. 拦截器配置**

RestTemplate也可以设置拦截器做一些统一处理。这个功能感觉和Spring MVC的拦截器类似。配置也很简单：

class MyInterceptor implements ClientHttpRequestInterceptor{
    
            @Override
            public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
                logger.info("enter interceptor...");
                return execution.execute(request,body);
            }
        }

@Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        RestTemplate restTemplate = new RestTemplate(factory);
        MyInterceptor myInterceptor = new MyInterceptor();
        List<ClientHttpRequestInterceptor> list = new ArrayList<>();
        list.add(myInterceptor);
        restTemplate.setInterceptors(list);
        return restTemplate;
    }

**2. ErrorHandler配置**

ErrorHandler用来对调用错误对统一处理。

public class MyResponseErrorHandler extends DefaultResponseErrorHandler {
    
            @Override
            public boolean hasError(ClientHttpResponse response) throws IOException {
                return super.hasError(response);
            }
    
            @Override
            public void handleError(ClientHttpResponse response) throws IOException {
                HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
                if (statusCode == null) {
                    throw new UnknownHttpStatusCodeException(response.getRawStatusCode(), response.getStatusText(),
                            response.getHeaders(), getResponseBody(response), getCharset(response));
                }
                handleError(response, statusCode);
            }
            @Override
            protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
                switch (statusCode.series()) {
                    case CLIENT_ERROR:
                        HttpClientErrorException exp1 = new HttpClientErrorException(statusCode, response.getStatusText(), response.getHeaders(), getResponseBody(response), getCharset(response));
                        logger.error("客户端调用异常",exp1);
                        throw  exp1;
                    case SERVER_ERROR:
                        HttpServerErrorException exp2 = new HttpServerErrorException(statusCode, response.getStatusText(),
                                response.getHeaders(), getResponseBody(response), getCharset(response));
                        logger.error("服务端调用异常",exp2);
                        throw exp2;
                    default:
                        UnknownHttpStatusCodeException exp3 = new UnknownHttpStatusCodeException(statusCode.value(), response.getStatusText(),
                                response.getHeaders(), getResponseBody(response), getCharset(response));
                        logger.error("网络调用未知异常");
                        throw exp3;
                }
            }
    
        }

@Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        RestTemplate restTemplate = new RestTemplate(factory);
        MyResponseErrorHandler errorHandler = new MyResponseErrorHandler();
        restTemplate.setErrorHandler(errorHandler);
        List<HttpMessageConverter<?>> messageConverters = restTemplate.getMessageConverters();
        //通过下面代码可以添加新的HttpMessageConverter
        //messageConverters.add(new );
        return restTemplate;
    }

**3. HttpMessageConverter配置**  
RestTemplate 也可以配置HttpMessageConverter，配置的原理和Spring MVC中类似。

### 简单总结[\#][Link 5] ###

通过RestTemplate，我们可以非常方便的进行Rest API调用。但是在Spring 5中已经不再建议使用RestTemplate，而是建议使用WebClient。WebClient是一个支持异步调用的Client。所以喜欢研究新东西的同学可以开始研究下新东西了。

## **同步RestTemplate和异步AsyncRestTemplate** ##

我编写了以下代码来测试同步RestTemplate和AsyncRestTemplate的性能.我只是在POSTMAN上手动运行了几次.

我们只是将10个引用传递给GET调用,以便我们可以返回10个链接：

RestTemplate – 同步并在2806ms返回：

ArrayList<String> references = new ArrayList<>();
    ArrayList<String> links = new ArrayList<>();
    RestTemplate restTemplate = new RestTemplate(); 
    restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
    for (int i = 0; i < 10; i++) {
        ResponseEntity<String> resource = restTemplate.getForEntity(references.get(i), String.class);
        links.add(resource.getBody().toString());
    }
    复制代码

RestTemplate – 异步并返回2794ms：

//Creating a synchronizedList so that when the async resttemplate returns, there will be no concurrency issues
    List<String> links = Collections.synchronizedList(new ArrayList<String>());
    
    //CustomClientHttpRequestFactory just extends SimpleClientHttpRequestFactory but disables automatic redirects in SimpleClientHttpRequestFactory
    CustomClientHttpRequestFactory customClientHttpRequestFactory = new CustomClientHttpRequestFactory();
    //Setting the ThreadPoolTaskExecutor for the Async calls
    org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor pool = new org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor();
    pool.setCorePoolSize(5);
    pool.setMaxPoolSize(10);
    pool.setWaitForTasksToCompleteOnShutdown(true);
    pool.initialize();
    //Setting the TaskExecutor to the ThreadPoolTaskExecutor
    customClientHttpRequestFactory.setTaskExecutor(pool);
    
    ArrayList<String> references = new ArrayList<>();
    ArrayList<String> links = new ArrayList<>();
    AsyncRestTemplate asyncRestTemplate = new AsyncRestTemplate(customClientHttpRequestFactory); 
    restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
    for (int i = 0; i < 10; i++) {
        Future<ResponseEntity<String>> resource = asyncRestTemplate.getForEntity(references.get(i), String.class);
        ResponseEntity<String> entity = resource.get(); //this should start up 10 threads to get the links asynchronously
        links.add(entity.getBody().toString());
    }
    复制代码

在大多数情况下,两种方法实际上都以非常相似的时间返回结果,在异步和同步调用中平均为2800ms.

我做错了什么,因为我希望异步调用更快？

最佳答案

我会说你在这里错过了AsyncRest的真正好处.  
您应该为要发送的每个请求添加回调,以便响应仅在可用时进行处理.

实际上,AsyncRestTemplate的getForEntity方法返回一个可以连接回调任务的ListenableFuture.有关详细信息,请参阅官方文档[ListenableFuture][].

例如,在您的情况下,它可能是：

for (int i = 0; i < 10; i++) {
         ListenableFuture<ResponseEntity<String>> response = asyncRestTemplate.getForEntity(references.get(i), String.class);
         response.addCallback(new ListenableFutureCallback<ResponseEntity<String>>() {
                @Override
                public void onSuccess(ResponseEntity<String> result) {
                    // Do stuff onSuccess 
                    links.add(result.getBody().toString());
                }
    
                @Override
                public void onFailure(Throwable ex) {
                    log.warn("Error detected while submitting a REST request. Exception was {}", ex.getMessage());
                }
            });
    }

# #

## RestTemplate整合HttpClient、Okhttp ##

## HttpClient入门 ##

*  确定maven环境

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.4.RELEASE</version>
        </parent>
    
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.apache.httpcomponents</groupId>
                <artifactId>httpclient</artifactId>
                <version>4.5.6</version>
            </dependency>
            
            <dependency>
                <groupId>lombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.0</version>
            </dependency>
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.49</version>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
            </dependency>
        </dependencies>

*  使用HttpClient发送Get请求

CloseableHttpClient httpClient = null;
            CloseableHttpResponse response = null;
    		try {
                //1 创建Httpclient对象(默认连接),相当于打开了浏览器
                CloseableHttpClient httpClient = HttpClients.createDefault();
    
                //2 确定请求方式和请求路径，相当于在浏览器输入地址
                HttpGet httpGet = new HttpGet("http://localhost:9090/user");
    
                //3 执行请求并获取响应，相当于敲完地址后按下回车。
                CloseableHttpResponse response = httpClient.execute(httpGet);
    
                //4 判断状态码
                if(response.getStatusLine().getStatusCode() == 200){
                    //5.1 获得响应数据的类型
                    System.out.println(response.getEntity().getContentType());
                    //5.2 获得响应体内容并使用EntityUtils工具进行处理
                    String str = EntityUtils.toString(response.getEntity(),"UTF-8");
                    System.out.println(str);
                }
    
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
              //6 释放资源
              response.close();
              httpClient.close();
            }

*  使用HttpClient发送Post请求
    
        CloseableHttpClient httpClient = null;
                CloseableHttpResponse response = null;
                try {
                    httpClient = HttpClients.createDefault();
        
                    HttpPost httpPost = new HttpPost("http://localhost:9090/user");
                    //  设置请求头
                    httpPost.setHeader("content-type","application/json;charset=utf-8");
                    //  设置并处理请求体
                    String str = "{\"username\":\"jack\",\"password\":\"1111\"}";
                    httpPost.setEntity(new StringEntity(str,"utf-8"));
        
                    response = httpClient.execute(httpPost);
        
                    if (response.getStatusLine().getStatusCode() == 200){
                        System.out.println(EntityUtils.toString(response.getEntity()));
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }finally {
                    response.close();
                    httpClient.close();
                }
 *  使用HttpClient发送Put请求
    
        CloseableHttpClient httpClient = null;
                CloseableHttpResponse response = null;
                try {
                    httpClient = HttpClients.createDefault();
                    HttpPut httpPut = new HttpPut("http://localhost:9090/user");
                    httpPut.setHeader("content-type","application/json;charset=utf-8");
                    String jsonStr = JSON.toJSONString(new User(1, "jack", "1111", 18));
                    httpPut.setEntity(new StringEntity(jsonStr,"utf-8"));
        
                    response = httpClient.execute(httpPut);
        
                    if (response.getStatusLine().getStatusCode() == 200){
                        System.out.println(EntityUtils.toString(response.getEntity()));
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    response.close();
                    httpClient.close();
                }
 *  使用HttpClient发送Delete请求
    
        CloseableHttpClient httpClient = null;
                CloseableHttpResponse response = null;
                try {
                    //1, 创建客户端
                    httpClient = HttpClients.createDefault();
                    //2, 创建DELETE实例
                    HttpDelete httpDelete = new HttpDelete("http://localhost:9090/user/1");
                    //3, 发送请求
                    response = httpClient.execute(httpDelete);
                    //4, 判断状态码
                    if (response.getStatusLine().getStatusCode() == 200){
                        //5, 实用工具处理响应数据
                        System.out.println(EntityUtils.toString(response.getEntity()));
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    //6, 释放资源
                    response.close();
                    httpClient.close();
                }

### 4.RestTemplate ###

*  RestTemplate是Spring提供的用于访问Rest服务的客户端，
    
     RestTemplate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
 *  Get请求
    
        [@Test](https://my.oschina.net/azibug)
            public void testGet(){
                RestTemplate restTemplate = new RestTemplate();
                //  设置url,返回值类型
                ResponseEntity<BaseResult> entity = restTemplate.getForEntity("http://localhost:9090/user", BaseResult.class);
                //  返回状态码
                System.out.println(entity.getStatusCode());
                //  返回响应体
                System.out.println(entity.getBody().getData());
            }
 *  Post请求
    
        [@Test](https://my.oschina.net/azibug)
            public void testLogin(){
                RestTemplate restTemplate = new RestTemplate();
                //  设置url,请求体(自动处理),返回值类型
                ResponseEntity<User> entity = restTemplate.postForEntity("http://localhost:9090/user/login", new User(1,"jack","1234",18), User.class);
                System.out.println(entity.getStatusCodeValue());
                System.out.println(entity.getBody());
            }
 *  Put请求
    
        [@Test](https://my.oschina.net/azibug)
            public void testPut(){
                RestTemplate restTemplate = new RestTemplate();
                 //  设置url
                restTemplate.put("http://localhost:9090/user",new User(1,"jack","1234",18));
                System.out.println("修改成功");
            }
 *  Delete请求
    
        [@Test](https://my.oschina.net/azibug)
            public void testDelete(){
                RestTemplate restTemplate = new RestTemplate();
                //  设置url
                restTemplate.delete("http://localhost:9090/user/1");
                System.out.println(" 删除成功");
            }

## 5.SpringBoot 整合 HttpClient及RestTemplate自定义连接池 ##

package com.czxy.config;
    
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.config.RequestConfig;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.HttpClients;
    import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
    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.web.client.RestTemplate;
    
    import java.nio.charset.Charset;
    import java.util.List;
    
    /**
     * Created by 澈 on 2019/12/3.
     */
    @Configuration
    public class HttpClientConfig {
    
        //1. 自定义连接 httpClient
        @Bean
        public CloseableHttpClient httpClient(PoolingHttpClientConnectionManager connectionManager,
                                              RequestConfig requestConfig){
            return HttpClients.custom()
                    .setConnectionManager(connectionManager)
                    .setDefaultRequestConfig(requestConfig)
                    .build();
        }
    
        //2. 配置PoolingHttpClientConnectionManager
        @Bean
        public PoolingHttpClientConnectionManager connectionManager(){
            //1.  HttpClient连接管理器
            PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
            //1.1.  最大连接数
            connectionManager.setMaxTotal(1000);
            //1.2.  设置并发访问数
            connectionManager.setDefaultMaxPerRoute(20);
    
            return connectionManager;
        }
    
        //3. 配置RequestConfig
        @Bean
        public RequestConfig requestConfig(){
            //1.3.  请求配置RequestConfig
            return RequestConfig.custom()
                    .setConnectTimeout(1000)
                    .setConnectionRequestTimeout(500)
                    .setSocketTimeout(10 * 1000)
                    .build();
        }
    
        //4. 创建一个工厂
        @Bean
        public ClientHttpRequestFactory requestFactory(HttpClient httpClient){
            return new HttpComponentsClientHttpRequestFactory(httpClient);
        }
    
        //5. 配置restTemplate
        @Bean
        public RestTemplate restTemplate(ClientHttpRequestFactory requestFactory){
            RestTemplate template = new RestTemplate(requestFactory);
            //乱码处理
            List<HttpMessageConverter<?>> list = template.getMessageConverters();
            for (HttpMessageConverter<?> mc : list) {
                if (mc instanceof StringHttpMessageConverter) {
                    ((StringHttpMessageConverter) mc).setDefaultCharset(Charset.forName("UTF-8"));
                }
            }
            return template;
        }
    }

## 6.整合SpringBoot测试类 ##

*  在测试代码中可以进行Spring容器的注册

package com.czxy;
    
    import com.alibaba.fastjson.JSON;
    import com.czxy.domain.User;
    import org.apache.http.client.config.RequestConfig;
    import org.apache.http.client.methods.CloseableHttpResponse;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.entity.StringEntity;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
    import org.apache.http.util.EntityUtils;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.web.client.RestTemplate;
    
    import javax.annotation.Resource;
    import java.io.IOException;
    
    /**
     * Created by 澈 on 2019/12/4.
     */
    @RunWith(SpringRunner.class)    //spring 整合junit
    @SpringBootTest(classes = HttpClientApplication.class)      //spring整合启动类
    public class Test04 {
      	
        @Resource
        private CloseableHttpClient httpClient;
        @Resource
        private RestTemplate restTemplate;
        @Resource
        private PoolingHttpClientConnectionManager connectionManager;
        @Resource
        private RequestConfig requestConfig;
    
        @Test
        public void testDemo02(){
            System.out.println(httpClient);
            System.out.println(restTemplate);
            System.out.println(connectionManager);
            System.out.println(requestConfig);
        }
    }

# [springboot装配OkHttp组件][springboot_OkHttp] #

在SpringBoot应用中，发送Http通常我们使用RestTemplate，但有部分组件底层是使用OkHttp进行Http的操作，而且OKHttp也是一个很优秀的HTTP组件。

RestTempate的springboot封装参考：[https://www.cnblogs.com/yangzhilong/p/6640207.html][https_www.cnblogs.com_yangzhilong_p_6640207.html]

application.yml

okhttp:
      connect-timeout-ms: 500
      keep-alive-duration-sec: 5000
      max-idle: 100
      read-timeout-ms: 500
      write-timeout-ms: 500

Configuration：

![复制代码][format_png 4]

import java.util.concurrent.TimeUnit;
    
    import javax.annotation.Resource;
    import javax.validation.constraints.NotNull;
    
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.context.annotation.Bean;
    import org.springframework.stereotype.Component;
    import org.springframework.validation.annotation.Validated;
    
    import com.longge.gateway.util.OkHttpUtils;
    
    import lombok.Getter;
    import lombok.Setter;
    import okhttp3.ConnectionPool;
    import okhttp3.OkHttpClient;
    
    /**
     * @author roger yang
     * @date 9/16/2019
     */
    public class OkHttpConfiguration {
        @Resource
        private OkHttpConfig okHttpConfig;
        
        @Bean
        public OkHttpClient okHttpClient() {
            OkHttpClient client = new OkHttpClient.Builder()
                    .retryOnConnectionFailure(false)
                    .connectionPool(pool())
                    .connectTimeout(okHttpConfig.getConnectTimeoutMs(), TimeUnit.MILLISECONDS)
                    .readTimeout(okHttpConfig.getReadTimeoutMs(), TimeUnit.MILLISECONDS)
                    .writeTimeout(okHttpConfig.getWriteTimeoutMs(),TimeUnit.MILLISECONDS)
                    .build();
            
            OkHttpUtils.setOkHttpClient(client);
            return client;
        }
        
        @Bean
        public ConnectionPool pool() {
            return new ConnectionPool(okHttpConfig.getMaxIdle(), okHttpConfig.getKeepAliveDurationSec(), TimeUnit.SECONDS);
        }
        
        @Component
        @ConfigurationProperties(prefix = "okhttp")
        @Getter
        @Setter
        @Validated
        static class OkHttpConfig {
            @NotNull
            private Long connectTimeoutMs;
            @NotNull
            private Long readTimeoutMs;
            @NotNull
            private Long writeTimeoutMs;
            @NotNull
            private Integer maxIdle;
            @NotNull
            private Long keepAliveDurationSec;
        }
    }

![复制代码][format_png 4]

Util帮助类：

![复制代码][format_png 4]

import java.io.IOException;
    import java.net.MalformedURLException;
    import java.net.URL;
    import java.util.Map;
    import java.util.Objects;
    
    import com.alibaba.fastjson.JSONObject;
    
    import lombok.NonNull;
    import okhttp3.Callback;
    import okhttp3.FormBody;
    import okhttp3.Headers;
    import okhttp3.MediaType;
    import okhttp3.OkHttpClient;
    import okhttp3.Request;
    import okhttp3.RequestBody;
    import okhttp3.Response;
    
    /**
     * 参数中Callback表示发送异步请求
     * @author roger yang
     * @date 9/16/2019
     */
    public class OkHttpUtils {
        private static OkHttpClient okHttpClient;
    
        public static void setOkHttpClient(OkHttpClient client) {
            okHttpClient = client;
        }
        
        /**
         * GET Method begin---------------------------------
         */
        
        public static <T> T get(@NonNull String url, Class<T> clasz) {
            return get(url, null, null, clasz);
        }
        
        public static void get(@NonNull String url, Callback callback) {
            get(url, null, null, callback);
        }
    
        public static <T> T get(@NonNull String url, Map<String, String> queryParameter, Class<T> clasz) {
            return get(url, null, queryParameter, clasz);
        }
        
        public static void get(@NonNull String url, Map<String, String> queryParameter, Callback callback) {
            get(url, null, queryParameter, callback);
        }
    
        public static <T> T get(@NonNull String url, Map<String, String> headerParameter, Map<String, String> queryParameter, Class<T> clasz) {
            Request request = processGetParameter(url, headerParameter, queryParameter);
    
            try (Response resp = okHttpClient.newCall(request).execute();) {
                return processResponse(resp, clasz);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        
        public static void get(@NonNull String url, Map<String, String> headerParameter, Map<String, String> queryParameter, Callback callback) {
            Request request = processGetParameter(url, headerParameter, queryParameter);
            okHttpClient.newCall(request).enqueue(callback);
        }
        
        private static Request processGetParameter(String url, Map<String, String> headerParameter, Map<String, String> queryParameter) {
            Request.Builder builder = new Request.Builder();
            if (!isEmptyMap(headerParameter)) {
                builder.headers(Headers.of(headerParameter));
            }
            if (isEmptyMap(queryParameter)) {
                builder.url(url);
            } else {
                boolean hasQuery = false;
                try {
                    hasQuery = new URL(url).getQuery().isEmpty();
                } catch (MalformedURLException e) {
                    throw new RuntimeException("url is illegal");
                }
                StringBuilder sb = new StringBuilder(url);
                if (!hasQuery) {
                    sb.append("?1=1");
                }
                queryParameter.forEach((k, v) -> {
                    sb.append("&").append(k).append("=").append(v);
                });
                builder.url(sb.toString());
            }
            return builder.build();
        }
    
        /**
         * POST Method With JSON begin---------------------------------
         */
        
        public static <T> T postJson(@NonNull String url, Class<T> clasz) {
            return postJson(url, null, null, clasz);
        }
        
        public static void postJson(@NonNull String url, Callback callback) {
            postJson(url, null, null, callback);
        }
    
        public static <T> T postJson(@NonNull String url, Map<String, String> headerParameter, Class<T> clasz) {
            return postJson(url, headerParameter, null, clasz);
        }
        
        public static void postJson(@NonNull String url, Map<String, String> headerParameter, Callback callback) {
            postJson(url, headerParameter, null, callback);
        }
        
        public static <T> T postJson(@NonNull String url, Map<String, String> headerParameter, Object bodyObj, Class<T> clasz) {
            Request request = processPostJsonParameter(url, headerParameter, bodyObj);
            try (Response resp = okHttpClient.newCall(request).execute();) {
                return processResponse(resp, clasz);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        public static void postJson(@NonNull String url, Map<String, String> headerParameter, Object bodyObj, Callback callback) {
            Request request = processPostJsonParameter(url, headerParameter, bodyObj);
            okHttpClient.newCall(request).enqueue(callback);
        }
        
        private static Request processPostJsonParameter(String url, Map<String, String> headerParameter, Object bodyObj) {
            Request.Builder builder = new Request.Builder().url(url);
            if(!Objects.isNull(bodyObj)) {
                RequestBody body = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), JSONObject.toJSONString(bodyObj));
                builder.post(body);
            } else {
                RequestBody body = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), "{}");
                builder.post(body);
            }
            if (!isEmptyMap(headerParameter)) {
                builder.headers(Headers.of(headerParameter));
            }
            return builder.build();
        }
        
        /**
         * POST Method With Form begin---------------------------------
         */
        
        public static <T> T postForm(@NonNull String url, Class<T> clasz) {
            return postForm(url, null, null, clasz);
        }
        
        public static void postForm(@NonNull String url, Callback callback) {
            postForm(url, null, null, callback);
        }
    
        public static <T> T postForm(@NonNull String url, Map<String, String> headerParameter, Class<T> clasz) {
            return postForm(url, headerParameter, null, clasz);
        }
        
        public static void postForm(@NonNull String url, Map<String, String> headerParameter, Callback callback) {
            postForm(url, headerParameter, null, callback);
        }
        
        public static <T> T postForm(@NonNull String url, Map<String, String> headerParameter, Map<String, String> parameters, Class<T> clasz) {
            Request request = processPostFormParameter(url, headerParameter, parameters);
            try (Response resp = okHttpClient.newCall(request).execute();) {
                return processResponse(resp, clasz);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        public static void postForm(@NonNull String url, Map<String, String> headerParameter, Map<String, String> parameters, Callback callback) {
            Request request = processPostFormParameter(url, headerParameter, parameters);
            okHttpClient.newCall(request).enqueue(callback);
        }
        
        private static Request processPostFormParameter(String url, Map<String, String> headerParameter, Map<String, String> parameters) {
            Request.Builder builder = new Request.Builder().url(url);
            if(!Objects.isNull(parameters)) {
                FormBody.Builder formBuilder = new FormBody.Builder();
                parameters.forEach((k, v) -> {
                    formBuilder.add(k, v);
                });
                builder.post(formBuilder.build());
            }
            if (!isEmptyMap(headerParameter)) {
                builder.headers(Headers.of(headerParameter));
            }
            return builder.build();
        }
        
        @SuppressWarnings("unchecked")
        private static <T> T processResponse(Response resp, Class<T> clasz) throws IOException {
            if (resp.isSuccessful()) {
                if (Objects.equals(Void.class, clasz)) {
                    return null;
                }
                String respStr = resp.body().string();
                if(Objects.equals(String.class, clasz)) {
                    return (T)respStr;
                }
                return JSONObject.parseObject(respStr, clasz);
            }
            return null;
        }
        
        private static boolean isEmptyMap(Map<? extends Object, ? extends Object> map) {
            return Objects.isNull(map) || map.isEmpty();
        }
    }

![复制代码][format_png 4]

GitHub地址：[https://github.com/yangzhilong/new-gateway-test.git][https_github.com_yangzhilong_new-gateway-test.git]

如果想要OkHttp的装配是非自动的，可以采用自定义@EnableXX注解来实现。

![复制代码][format_png 4]

import java.lang.annotation.Documented;
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    import org.springframework.context.annotation.Import;
    
    import com.longge.gateway.configuration.OkHttpConfiguration;
    
    /**
     * @author roger yang
     * @date 9/16/2019
     */
     @Target(ElementType.TYPE)
     @Retention(RetentionPolicy.RUNTIME)
     @Documented
     @Import(OkHttpConfiguration.class)
    public @interface EnableOkHttp {
    
    }

![复制代码][format_png 4]

然后把OkHttpConfiguration类的@Configuration注解去掉，当你要用时在启动类加上@EnableOkHttp即可。

对于OKhttp的设置还可参考：

1、简介

OkHttp是一个高效的HTTP客户端，允许所有同一个主机地址的请求共享同一个socket连接；连接池减少请求延时；透明的GZIP压缩减少响应数据的大小；缓存响应内容，避免一些完全重复的请求

当网络出现问题的时候OkHttp依然坚守自己的职责，它会自动恢复一般的连接问题，如果你的服务有多个IP地址，当第一个IP请求失败时，OkHttp会交替尝试你配置的其他IP，OkHttp使用现代TLS技术(SNI, ALPN)初始化新的连接，当握手失败时会回退到TLS 1.0。

1）使用：它的请求/响应 API 使用构造器模式builders来设计，它支持阻塞式的同步请求和带回调的异步请求。

<dependency>
        <groupId>com.squareup.okhttp3</groupId>
        <artifactId>okhttp</artifactId>
        <version>3.10.0</version>
    </dependency>

import okhttp3.ConnectionPool;
    import okhttp3.OkHttpClient;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.http.client.ClientHttpRequestFactory;
    import org.springframework.http.client.OkHttp3ClientHttpRequestFactory;
    import org.springframework.web.client.RestTemplate;
    
    import javax.net.ssl.SSLContext;
    import javax.net.ssl.SSLSocketFactory;
    import javax.net.ssl.TrustManager;
    import javax.net.ssl.X509TrustManager;
    import java.security.KeyManagementException;
    import java.security.NoSuchAlgorithmException;
    import java.security.SecureRandom;
    import java.security.cert.CertificateException;
    import java.security.cert.X509Certificate;
    import java.util.concurrent.TimeUnit;
    
    @Configuration
    public class OkHttpRestTemplateConfig {
    
    
        @Bean("okHttpRestTemplate")
        public RestTemplate okHttpRestTemplate() {
            OkHttpClient httpClient = okHttpClient();
            ClientHttpRequestFactory factory = new OkHttp3ClientHttpRequestFactory(httpClient);
            RestTemplate restTemplate = new RestTemplate(factory);
            // 可以添加消息转换
            //restTemplate.setMessageConverters(...);
            // 可以增加拦截器
            //restTemplate.setInterceptors(...);
            return restTemplate;
        }
    
        @Bean
        public OkHttpClient okHttpClient() {
            return new OkHttpClient.Builder()
                    //.sslSocketFactory(sslSocketFactory(), x509TrustManager())
                    .retryOnConnectionFailure(false)
                    .connectionPool(pool())
                    .connectTimeout(30, TimeUnit.SECONDS)
                    .readTimeout(30, TimeUnit.SECONDS)
                    .writeTimeout(30,TimeUnit.SECONDS)
                    .build();
        }
    
        @Bean
        public X509TrustManager x509TrustManager() {
            return new X509TrustManager() {
                @Override
                public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
                }
                @Override
                public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
                }
                @Override
                public X509Certificate[] getAcceptedIssuers() {
                    return new X509Certificate[0];
                }
            };
        }
    
        @Bean
        public SSLSocketFactory sslSocketFactory() {
            try {
                //信任任何链接
                SSLContext sslContext = SSLContext.getInstance("TLS");
                sslContext.init(null, new TrustManager[]{x509TrustManager()}, new SecureRandom());
                return sslContext.getSocketFactory();
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            } catch (KeyManagementException e) {
                e.printStackTrace();
            }
            return null;
        }
    
        /**
         * Create a new connection pool with tuning parameters appropriate for a single-user application.
         * The tuning parameters in this pool are subject to change in future OkHttp releases. Currently
         */
        @Bean
        public ConnectionPool pool() {
            return new ConnectionPool(200, 5, TimeUnit.MINUTES);
        }
    }

[format_png]: /images/20221123/b8af40b053b04d7e8d914a1d7e52da03.png
[format_png 1]: /images/20221123/9f89a72f2b9b46079b315ec0c344ce1e.png
[format_png 2]: /images/20221123/145fd4f84ce4411e9fe4afcd2a93c11a.png
[RestTemplate]: https://docs.spring.io/spring/docs/5.1.9.RELEASE/spring-framework-reference/integration.html#rest-resttemplate
[Link 1]: https://www.cnblogs.com/54chensongxia/p/11414923.html#4193522356
[format_png 3]: /images/20221123/8886078dec8842e7af5f70c54942f891.png
[format_png 3 1]: https://img2018.cnblogs.com/blog/1775037/201908/1775037-20190826210413003-1181713678.png
[Link 2]: https://www.cnblogs.com/54chensongxia/p/11414923.html#546250687
[Link 3]: https://www.cnblogs.com/54chensongxia/p/11414923.html#2503930806
[Link 4]: https://www.cnblogs.com/54chensongxia/p/11414923.html#4223406319
[Link 5]: https://www.cnblogs.com/54chensongxia/p/11414923.html#2007155645
[ListenableFuture]: http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/util/concurrent/ListenableFuture.html
[springboot_OkHttp]: https://www.cnblogs.com/yangzhilong/p/11527545.html
[https_www.cnblogs.com_yangzhilong_p_6640207.html]: https://www.cnblogs.com/yangzhilong/p/6640207.html
[format_png 4]: /images/20221123/8e3f7ce59fb948c38bca207c7346c162.png
[https_github.com_yangzhilong_new-gateway-test.git]: https://github.com/yangzhilong/new-gateway-test.git