我们在项目中经常需要与HTTP服务器进行通信，Spring框架提供了
RestTemplate类，可以很方便的与HTTP服务器进行通信。
一、介绍
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。
调用RestTemplate的默认构造函数，RestTemplate对象在底层通过使用java.net包下的实现创建HTTP请求，可以通过使用ClientHttpRequestFactory指定不同的HTTP请求方式。
ClientHttpRequestFactory接口主要提供了两种实现方式
一种是SimpleClientHttpRequestFactory，使用J2SE提供的方式（既java.net包提供的方式）创建底层的HTTP请求连接。
一种方式是使用HttpComponentsClientHttpRequestFactory方式，底层使用HttpClient访问远程的HTTP服务，使用HttpClient可以配置连接池和证书等信息。
二、Spring项目中的配置
下面介绍RestTemplate在Spring项目中的配置
1、简单配置(用法)
xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util-3.0.xsd">
<!--简单的声明Bean即可--->
<bean id="restTemplate" class="org.springframework.web.client.RestTemplate"/>
</beans>
2、配合配置链接属性(用法)
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd"
default-autowire="byName" default-lazy-init="true">
<!--方式一、使用jdk的实现-->
<bean id="requestFactory" class="org.springframework.http.client.SimpleClientHttpRequestFactory">
<property name="readTimeout" value="10000"/>
<property name="connectTimeout" value="5000"/>
</bean>
<bean id="simpleRestTemplate" class="org.springframework.web.client.RestTemplate">
<constructor-arg ref="requestFactory"/>
<property name="messageConverters">
<list>
<bean class="org.springframework.http.converter.FormHttpMessageConverter"/>
<bean class="org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter"/>
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
<bean class="org.springframework.http.converter.StringHttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<value>text/plain;charset=UTF-8</value>
</list>
</property>
</bean>
</list>
</property>
</bean>
</beans>
3、使用连接池的配置
<!--使用httpclient的实现，带连接池-->
<!--在httpclient4.3版本后才有-->
<bean id="httpClientBuilder" class="org.apache.http.impl.client.HttpClientBuilder" factory-method="create">
<property name="connectionManager">
<bean class="org.apache.http.impl.conn.PoolingHttpClientConnectionManager">
<!--整个连接池的并发-->
<property name="maxTotal" value="50"/>
<!--每个主机的并发-->
<property name="defaultMaxPerRoute" value="50"/>
</bean>
</property>
<!--开启重试-->
<property name="retryHandler">
<bean class="org.apache.http.impl.client.DefaultHttpRequestRetryHandler">
<constructor-arg value="2"/>
<constructor-arg value="true"/>
</bean>
</property>
<property name="defaultHeaders">
<list>
<bean class="org.apache.http.message.BasicHeader">
<constructor-arg value="Content-Type"/>
<constructor-arg value="text/html;charset=UTF-8"/>
</bean>
<bean class="org.apache.http.message.BasicHeader">
<constructor-arg value="Accept-Encoding"/>
<constructor-arg value="gzip,deflate"/>
</bean>
<bean class="org.apache.http.message.BasicHeader">
<constructor-arg value="Accept-Language"/>
<constructor-arg value="zh-CN"/>
</bean>
</list>
</property>
</bean>
<bean id="httpClient" factory-bean="httpClientBuilder" factory-method="build"/>
<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
<property name="messageConverters">
<list value-type="org.springframework.http.converter.HttpMessageConverter">
<bean class="org.springframework.http.converter.StringHttpMessageConverter">
<property name="supportedMediaTypes">
<value>text/html;charset=UTF-8</value>
</property>
</bean>
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="supportedMediaTypes">
<value>application/json;charset=UTF-8</value>
</property>
</bean>
<bean class="org.springframework.http.converter.ResourceHttpMessageConverter"/>
<bean class="org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter"/>
<bean class="org.springframework.http.converter.FormHttpMessageConverter"/>
<bean class="org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter"/>
</list>
</property>
<property name="requestFactory">
<bean class="org.springframework.http.client.HttpComponentsClientHttpRequestFactory">
<constructor-arg ref="httpClient"/>
<!--连接时间(毫秒)-->
<property name="connectTimeout" value="20000"/>
<!--读取时间(毫秒)-->
<property name="readTimeout" value="20000"/>
</bean>
</property>
</bean>
三、常用方法
1、POST方法
public <T> T postForObject(String url, Object request, Class<T> responseType, Object... uriVariables)
throws RestClientException
public <T> T postForObject(String url, Object request, Class<T> responseType, Map<String, ?> uriVariables)
throws RestClientException
public <T> T postForObject(URI url, Object request, Class<T> responseType) throws RestClientException
使用示例:
@Autowired
private RestTemplate restTemplate;
public void testPost(){
HttpHeaders headers = new HttpHeaders();
headers.add("X-Auth-Token", "e348bc22-5efa-4299-9142-529f07a18ac9");
MultiValueMap<String, String> postParameters = new LinkedMultiValueMap<String, String>();
postParameters.add("owner", "11");
postParameters.add("subdomain", "aoa");
postParameters.add("comment", "");
HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<MultiValueMap<String, String>>(postParameters, headers);
ParseResultVo exchange = null;
try {
exchange = restTemplate.postForObject("http://l-dnsutil1.ops.beta.cn6.qunar.com:10085/v1/cnames/tts.piao", requestEntity, ParseResultVo.class);
logger.info(exchange.toString());
} catch (RestClientException e) {
logger.error(e);
}
}
2、GET方法
public <T> T getForObject(String url, Class<T> responseType, Object... urlVariables) throws RestClientException
public <T> T getForObject(String url, Class<T> responseType, Map<String, ?> urlVariables) throws RestClientException
public <T> T getForObject(URI url, Class<T> responseType) throws RestClientException
使用示例:
@Autowired
private RestTemplate restTemplate;
public void testGet(){
String result = restTemplate.getForObject("https://www.baidu.com", String.class);
System.out.println(result);
}
