RestTemplate是Spring提供的用于访问Rest服务的客户端，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。RestTemplate 默认使用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（SimpleClientHttpRequestFactory），不需要配置证书信息，但如果调用https请求时的证书不合法，会报”unable to find valid certification path to requested target“错误。这时可以使用HttpComponentsClientHttpRequestFactory方式，底层使用HttpClient访问远程的Http服务来配置证书。

代码如下：

import java.security.KeyManagementException;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import javax.net.ssl.SSLContext;

import org.apache.http.client.config.RequestConfig;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.conn.ssl.TrustStrategy;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("httpClientFactory")
public class HttpClientFactory {

    @Value("${restclient.readTimeout}")
    private int readTimeout;

    @Value("${restclient.connectTimeout}")
    private int connectTimeout;

    public CloseableHttpClient acceptsUntrustedCertsHttpClient() throws NoSuchAlgorithmException,
            KeyManagementException, KeyStoreException {
        SSLContext sslcontext = SSLContexts.custom().setSecureRandom(new SecureRandom())
                .loadTrustMaterial(null, new TrustStrategy() {

                    public boolean isTrusted(X509Certificate[] chain, String authType) throws CertificateException {
                        return true;
                    }
                }).build();
        SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
                SSLConnectionSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);

        RequestConfig defaultRequestConfig = RequestConfig.custom().setSocketTimeout(readTimeout)
                .setConnectTimeout(connectTimeout).setStaleConnectionCheckEnabled(true).build();

        return HttpClients.custom().setSSLSocketFactory(sslsf).setDefaultRequestConfig(defaultRequestConfig).build();
    }
}
初始化httpClient

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd          
      http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
      http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
      http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">


    <bean id="httpClient" factory-bean="httpClientFactory" factory-method="acceptsUntrustedCertsHttpClient" />

    <bean id="clientHttpRequestFactory" class="org.springframework.http.client.HttpComponentsClientHttpRequestFactory">
        <constructor-arg ref="httpClient" />
    </bean>

    <bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
        <constructor-arg index="0">
            <list>
                <bean id="byteArrayHttpMessageConverter" class="org.springframework.http.converter.ByteArrayHttpMessageConverter"></bean>
                <bean id="stringHttpMessageConverter" class="org.springframework.http.converter.StringHttpMessageConverter">
                    <constructor-arg value="UTF-8"></constructor-arg>
                </bean>
                <bean id="resourceHttpMessageConverter" class="org.springframework.http.converter.ResourceHttpMessageConverter"></bean>
                <bean id="sourceHttpMessageConverter" class="org.springframework.http.converter.xml.SourceHttpMessageConverter"></bean>
                <bean id="allEncompassingFormHttpMessageConverter" class="org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter"></bean>
            </list>
        </constructor-arg>
        <property name="requestFactory" ref="clientHttpRequestFactory" />
    </bean>
</beans>

配置resttemplate