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：
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：
| HTTP method | RestTemplate methods |
|---|---|
| DELETE | delete |
| GET | getForObject |
| getForEntity | |
| HEAD | headForHeaders |
| OPTIONS | optionsForAllow |
| POST | postForLocation |
| postForObject | |
| PUT | put |
| any | exchange |
| execute |
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}
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。
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
: 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
#
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
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
#
@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
#
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
#
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
#
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
<!--确定spring boot的版本-->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.4.RELEASE</version>
</parent>
<dependencies>
<!--web起步依赖-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--httpclient-->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.6</version>
</dependency>
<!--支持lombok-->
<dependency>
<groupId>lombok</groupId>
<artifactId>lombok</artifactId>
<version>1.0</version>
</dependency>
<!--fastjson-->
<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
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
application.yml
okhttp:
connect-timeout-ms: 500
keep-alive-duration-sec: 5000
max-idle: 100
read-timeout-ms: 500
write-timeout-ms: 500Configuration：
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;
}
}
Util帮助类：
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();
}
}
GitHub地址：
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。
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 {
}
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);
}
}
版权声明：本文为u014748504原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。