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 registry = RegistryBuilder.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
 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 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 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 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> httpEntity=new HttpEntity<>(param);

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