Spring Boot 3中使用RestTemplate发送带请求体的GET请求

优先方案：自定义RestTemplate配置 #

Spring Boot 3 默认使用 HttpClient 5，而 HttpClient 5 会默认禁止 GET 请求携带请求体，因此需要先配置支持该行为的 HttpClient 实例，再注入到 RestTemplate 中。

1. 配置支持GET带请求体的RestTemplate #

创建配置类，构建允许GET请求带请求体的HttpClient，并设置为RestTemplate的请求工厂：

import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.HttpMethod;
import org.apache.hc.core5.http.config.HttpConfig;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate() {
        // 构建HttpClient，允许GET请求携带请求体
        CloseableHttpClient httpClient = HttpClients.custom()
                .setDefaultHttpConfig(HttpConfig.custom()
                        .setAllowRequestBodyForHttpMethods(HttpMethod.GET)
                        .build())
                .build();

        HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);
        return new RestTemplate(requestFactory);
    }
}

2. 使用RestTemplate发送带请求体的GET请求 #

注入上述配置的RestTemplate，构造包含请求体的HttpEntity，调用exchange方法发送请求：

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.web.client.RestTemplate;

// 通过依赖注入获取RestTemplate
private final RestTemplate restTemplate;

public String sendGetRequestWithBody(String serverUrl, Object requestBody) {
    // 设置请求头
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_JSON);
    
    // 构造包含请求体的请求实体
    HttpEntity<Object> requestEntity = new HttpEntity<>(requestBody, headers);
    
    // 发送GET请求并获取响应
    return restTemplate.exchange(
            serverUrl,
            HttpMethod.GET,
            requestEntity,
            String.class
    ).getBody();
}

备选方案：直接使用HttpClient 5发送请求 #

如果不需要RestTemplate的封装，可直接配置HttpClient 5发送带请求体的GET请求：

import org.apache.hc.client5.http.classic.methods.HttpGet;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.core5.http.ContentType;
import org.apache.hc.core5.http.HttpMethod;
import org.apache.hc.core5.http.config.HttpConfig;
import org.apache.hc.core5.http.io.entity.StringEntity;
import org.apache.hc.core5.http.io.entity.EntityUtils;

public void sendGetWithBodyDirectly() throws Exception {
    // 构建支持GET带请求体的HttpClient
    try (CloseableHttpClient httpClient = HttpClients.custom()
            .setDefaultHttpConfig(HttpConfig.custom()
                    .setAllowRequestBodyForHttpMethods(HttpMethod.GET)
                    .build())
            .build()) {
            
        HttpGet httpGet = new HttpGet("http://your-server-url");
        // 设置请求体
        String requestBody = "{\"param1\": \"value1\", \"param2\": \"value2\"}";
        StringEntity entity = new StringEntity(requestBody, ContentType.APPLICATION_JSON);
        httpGet.setEntity(entity);
        
        // 执行请求并解析响应
        try (var response = httpClient.execute(httpGet)) {
            String responseBody = EntityUtils.toString(response.getEntity());
            // 处理响应内容
            System.out.println(responseBody);
        }
    }
}

关键说明 #

HttpClient 5 默认会校验HTTP方法与请求体的合法性，通过setAllowRequestBodyForHttpMethods(HttpMethod.GET)可以关闭GET请求的请求体校验，从而支持带请求体的GET请求。

内容的提问来源于stack exchange，提问作者keemahs