restTemplate配置及使用

1 场景
java开发中，使用http连接，访问第三方网络接口，通常使用的连接工具为HttpClient和OKHttp。

这两种连接工具，使用起来比较复杂，新手容易出问题。如果使用spring框架，可以使用restTemplate来进行http连接请求。

restTemplate默认的连接方式是java中的HttpConnection，可以使用ClientHttpRequestFactory指定不同的HTTP连接方式。

2 依赖
maven依赖如下：

org.springframework spring-web 5.2.2.RELEASE org.apache.httpcomponents httpclient 4.5.7 3 配置 import org.apache.http.client.HttpClient; import org.apache.http.conn.HttpClientConnectionManager; import org.apache.http.impl.client.HttpClientBuilder; 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.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig {

/**
 * http连接管理器
 * @return
 */
@Bean
public HttpClientConnectionManager poolingHttpClientConnectionManager() {
    /*// 注册http和https请求
    Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
            .register("http", PlainConnectionSocketFactory.getSocketFactory())
            .register("https", SSLConnectionSocketFactory.getSocketFactory())
            .build();
    PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager(registry);*/
    
    PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager();
    // 最大连接数
    poolingHttpClientConnectionManager.setMaxTotal(500);
    // 同路由并发数（每个主机的并发）
    poolingHttpClientConnectionManager.setDefaultMaxPerRoute(100);
    return poolingHttpClientConnectionManager;
}

/**
 * HttpClient
 * @param poolingHttpClientConnectionManager
 * @return
 */
@Bean
public HttpClient httpClient(HttpClientConnectionManager poolingHttpClientConnectionManager) {
    HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
    // 设置http连接管理器
    httpClientBuilder.setConnectionManager(poolingHttpClientConnectionManager);
    
    /*// 设置重试次数
    httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(3, true));*/
    
    // 设置默认请求头
    /*List<Header> headers = new ArrayList<>();
    headers.add(new BasicHeader("Connection", "Keep-Alive"));
    httpClientBuilder.setDefaultHeaders(headers);*/
    
    return httpClientBuilder.build();
}

/**
 * 请求连接池配置
 * @param httpClient
 * @return
 */
@Bean
public ClientHttpRequestFactory clientHttpRequestFactory(HttpClient httpClient) {
    HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
    // httpClient创建器
    clientHttpRequestFactory.setHttpClient(httpClient);
    // 连接超时时间/毫秒（连接上服务器(握手成功)的时间，超出抛出connect timeout）
    clientHttpRequestFactory.setConnectTimeout(5 * 1000);
    // 数据读取超时时间(socketTimeout)/毫秒（务器返回数据(response)的时间，超过抛出read timeout）
    clientHttpRequestFactory.setReadTimeout(10 * 1000);
    // 连接池获取请求连接的超时时间，不宜过长，必须设置/毫秒（超时间未拿到可用连接，会抛出org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool）
    clientHttpRequestFactory.setConnectionRequestTimeout(10 * 1000);
    return clientHttpRequestFactory;
}

/**
 * rest模板
 * @return
 */
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory clientHttpRequestFactory) {
    // boot中可使用RestTemplateBuilder.build创建
    RestTemplate restTemplate = new RestTemplate();
    // 配置请求工厂
    restTemplate.setRequestFactory(clientHttpRequestFactory);
    return restTemplate;
}

}
4 使用
使用到的实体类如下：

@Data
@ToString
public class TempUser implements Serializable {
private String userName;
private Integer age;
}
4.1 GET请求
后台接口代码：

@RequestMapping(“getUser”)
public TempUser getUser(TempUser form) {
TempUser tempUser = new TempUser();
tempUser.setUserName(form.getUserName());
tempUser.setAge(form.getAge());
return tempUser;
}
4.1.1 普通访问
TempUser result = restTemplate.getForObject(“http://localhost:8080/cs-admin/rest/getUser?userName=张三&age=18”, TempUser.class);
4.1.2 返回HTTP状态
ResponseEntity responseEntity = restTemplate.getForEntity(“http://localhost:8080/cs-admin/rest/getUser?userName=张三&age=18”, TempUser.class);
// 获取状态对象
HttpStatus httpStatus = responseEntity.getStatusCode();
// 获取状态码
int statusCodeValue = responseEntity.getStatusCodeValue();
// 获取headers
HttpHeaders httpHeaders = responseEntity.getHeaders();
// 获取body
TempUser result = responseEntity.getBody();
4.1.3 映射请求参数
Map<String, Object> paramMap = new HashMap<>();
paramMap.put(“userName”, “张三”);
paramMap.put(“age”, 18);
TempUser result = restTemplate.getForObject(“http://localhost:8080/cs-admin/rest/getUser?userName={userName}&age={age}”, TempUser.class, paramMap);
4.2 POST请求
4.2.1 普通访问
后台接口代码：

RequestMapping(“getPostUser”)
public TempUser getPostUser(@RequestBody TempUser form) {
TempUser tempUser = new TempUser();
tempUser.setUserName(form.getUserName());
tempUser.setAge(form.getAge());
return tempUser;
}
（1）普通访问接口

TempUser param = new TempUser();
param.setUserName(“张三”);
param.setAge(18);
TempUser result = restTemplate.postForObject(“http://localhost:8080/cs-admin/rest/getPostUser”, param, TempUser.class);
（2）带HEAD访问接口

// 请求头信息
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.valueOf(“application/json;charset=UTF-8”));
//headers.add(“headParam1”, “headParamValue”);

// 请求体内容
TempUser param = new TempUser();
param.setUserName(“张三”);
param.setAge(18);

// 组装请求信息
HttpEntity httpEntity=new HttpEntity<>(param,headers);

TempUser result = restTemplate.postForObject(“http://localhost:8080/cs-admin/rest/getPostUser”, httpEntity, TempUser.class);
4.2.2 无请求体的访问
仅method为post，传参方式仍然为get的param方式

后台接口代码：

@RequestMapping(“getPostUserNoBody”)
public TempUser getPostUserNoBody(TempUser form) {
TempUser tempUser = new TempUser();
tempUser.setUserName(form.getUserName());
tempUser.setAge(form.getAge());
return tempUser;
}
访问方式：

Map<String, Object> paramMap = new HashMap<>();
paramMap.put(“userName”, “张三”);
paramMap.put(“age”, 18);
TempUser result = restTemplate.postForObject(“http://localhost:8080/cs-admin/rest/getPostUserNoBody?userName={userName}&age={age}”, null, TempUser.class, paramMap);
System.out.println(result);
4.3 上传文件
后台接口代码：

@RequestMapping(“uploadFile”)
public TempUser uploadFile(HttpServletRequest request, TempUser form) {
MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
//获取文件信息
MultipartFile multipartFile = multipartHttpServletRequest.getFile(“file”);
TempUser tempUser = new TempUser();
if (multipartFile != null) {
tempUser.setUserName(form.getUserName()+" "+multipartFile.getOriginalFilename());
}
if(form!=null){
tempUser.setAge(form.getAge());
}
return tempUser;
}
访问方式：

// 文件
FileSystemResource file=new FileSystemResource(“D:\Elasticsearch权威指南（中文版）.pdf”);

// 设置请求内容
MultiValueMap<String, Object> param=new LinkedMultiValueMap<>();
param.add(“file”, file);
// 其他参数
param.add(“userName”, “张三”);
param.add(“age”, 18);

// 组装请求信息
HttpEntity<MultiValueMap<String, Object>> httpEntity=new HttpEntity<>(param);

// 发送请求
TempUser result = restTemplate.postForObject(“http://localhost:8080/cs-admin/rest/uploadFile”, httpEntity, TempUser.class);

restTemplate配置及使用

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