Spring boot 发起http请求的简单用法

java后端发起http请求的方法经过不断演化（HttpURLConnection->HttpClient->CloseableHttpClient->RestTemplate），变得越来越简单方便。
Spingboot项目通过下面的配置，即可直接注入使用restTemplate很方便地发起http请求。

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig {
	@Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory){
        RestTemplate template = new RestTemplate(factory);
		StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter(Charset.forName("UTF-8"));  //避免中文乱码
		List<HttpMessageConverter<?>> list= new ArrayList<HttpMessageConverter<?>>();  
		list.add(stringHttpMessageConverter);  
		template.setMessageConverters(list);  
        return template;
    }
 
    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory(){
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setConnectTimeout(15000);
        factory.setReadTimeout(5000);
        return factory;
    }
}

调用restTemplate.getXXX()或postXXX()等方法即可发起对应Method的http请求。特殊的请求头和请求体可以在request参数里使用HttpEntity。如调用下面这个方法可以把data封装成xml请求：

HttpEntity<String> genXmlRequest(Object data) {
	HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_XML);
    String body = XmlUtils.stringify(data, "xml");
    return new HttpEntity<String>(body, headers);
}