RestTemplate使用详解

1.RestTemplate添加RequestHeader如content-type可通过httpclient设置

        List<Header> headers = new ArrayList<>();
        headers.add(new BasicHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.16 Safari/537.36"));
        headers.add(new BasicHeader("Accept-Encoding", "gzip,deflate"));
        headers.add(new BasicHeader("Accept-Language", "zh-CN"));
        headers.add(new BasicHeader("Connection", "Keep-Alive"));

        httpClientBuilder.setDefaultHeaders(headers);

        HttpClient httpClient = httpClientBuilder.build();

        // httpClient连接配置，底层是配置RequestConfig
        HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);

        restTemplate.setRequestFactory(clientHttpRequestFactory);

2.使用中进行异常处理

try catch

    public String postRemoteData(ParameterRo ro) throws UnsupportedEncodingException {
        /**
         * 设置请求头
         */
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.parseMediaType("application/json;charset=UTF-8"));
        headers.add("Accept", MediaType.APPLICATION_JSON.toString());

        /**
         * POST请求参数，根据需要进行封装
         */
        String bodyData = new String(Base64Util.encodeData(JSON.toJSONString(ro)).getBytes("UTF-8"), "UTF-8");

        /**
         * 查看HttpEntity的构造方法，包含只有请求头和只有请求体的情况
         */
        HttpEntity<String> httpEntity = new HttpEntity<String>(bodyData, headers);

        /**
         * 执行操作
         */
        String result = restTemplate.postForObject(remoteUrl, httpEntity, String.class);

        return result;
    }

3.控制超时，使用连接池，编码转换

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。

　　RestTemplate默认是使用SimpleClientHttpRequestFactory，内部是调用jdk的HttpConnection，默认超时为-1

   public RestTemplate(ClientHttpRequestFactory requestFactory) {
    this();
    setRequestFactory(requestFactory);
   }

其中，第二个构造方法中可以传入ClientHttpRequestFactory参数，第一个进行默认初始化，因为我们经常需要对请求超时进行设置并能 够对超时进行后续处理，而第      一个构造方法，我们无法控制超时时间，第二个构造中的ClientHttpRequestFactory接口的实现类中存在 timeout属性，因此选用第二个构造方法

//创建HTTP客户端工厂 private ClientHttpRequestFactory createFactory() { if (this.maxTotalConnect <= 0) { SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory(); factory.setConnectTimeout(this.connectTimeout); factory.setReadTimeout(this.readTimeout); return factory; } HttpClient httpClient = HttpClientBuilder.create().setMaxConnTotal(this.maxTotalConnect) .setMaxConnPerRoute(this.maxConnectPerRoute).build(); HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory( httpClient); factory.setConnectTimeout(this.connectTimeout); factory.setReadTimeout(this.readTimeout); return factory; } //初始化RestTemplate,并加入spring的Bean工厂，由spring统一管理 @Bean @ConditionalOnMissingBean(RestTemplate.class) public RestTemplate getRestTemplate() { RestTemplate restTemplate = new RestTemplate(this.createFactory()); List<HttpMessageConverter<?>> converterList = restTemplate.getMessageConverters(); //重新设置StringHttpMessageConverter字符集为UTF-8，解决中文乱码问题 HttpMessageConverter<?> converterTarget = null; for (HttpMessageConverter<?> item : converterList) { if (StringHttpMessageConverter.class == item.getClass()) { converterTarget = item; break; } } if (null != converterTarget) { converterList.remove(converterTarget); } converterList.add(1, new StringHttpMessageConverter(StandardCharsets.UTF_8)); //加入FastJson转换器 converterList.add(new FastJsonHttpMessageConverter4()); return restTemplate; }

@Bean public HttpMessageConverters fastjsonConverter() { FastJsonConfig fastJsonConfig = new FastJsonConfig(); //自定义格式化输出 fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat, SerializerFeature.WriteNullStringAsEmpty, SerializerFeature.WriteNullNumberAsZero); FastJsonHttpMessageConverter4 fastjson = new FastJsonHttpMessageConverter4(); fastjson.setFastJsonConfig(fastJsonConfig); return new HttpMessageConverters(fastjson); }

@Component
@Lazy(false)
public class RestClient {

    private static final Logger LOGGER = LoggerFactory.getLogger(SimpleRestClient.class);

    private static RestTemplate restTemplate;

    static {
        // 长连接保持30秒
        PoolingHttpClientConnectionManager pollingConnectionManager = new PoolingHttpClientConnectionManager(30, TimeUnit.SECONDS);
        // 总连接数
        pollingConnectionManager.setMaxTotal(1000);
        // 同路由的并发数
        pollingConnectionManager.setDefaultMaxPerRoute(1000);

        HttpClientBuilder httpClientBuilder = HttpClients.custom();
        httpClientBuilder.setConnectionManager(pollingConnectionManager);
        // 重试次数，默认是3次，没有开启
        httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(2, true));
        // 保持长连接配置，需要在头添加Keep-Alive
        httpClientBuilder.setKeepAliveStrategy(new DefaultConnectionKeepAliveStrategy());

//        RequestConfig.Builder builder = RequestConfig.custom();
//        builder.setConnectionRequestTimeout(200);
//        builder.setConnectTimeout(5000);
//        builder.setSocketTimeout(5000);
//
//        RequestConfig requestConfig = builder.build();
//        httpClientBuilder.setDefaultRequestConfig(requestConfig);

        List<Header> headers = new ArrayList<>();
        headers.add(new BasicHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.16 Safari/537.36"));
        headers.add(new BasicHeader("Accept-Encoding", "gzip,deflate"));
        headers.add(new BasicHeader("Accept-Language", "zh-CN"));
        headers.add(new BasicHeader("Connection", "Keep-Alive"));

        httpClientBuilder.setDefaultHeaders(headers);

        HttpClient httpClient = httpClientBuilder.build();

        // httpClient连接配置，底层是配置RequestConfig
        HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);
        // 连接超时
        clientHttpRequestFactory.setConnectTimeout(5000);
        // 数据读取超时时间，即SocketTimeout
        clientHttpRequestFactory.setReadTimeout(5000);
        // 连接不够用的等待时间，不宜过长，必须设置，比如连接不够用时，时间过长将是灾难性的
        clientHttpRequestFactory.setConnectionRequestTimeout(200);
        // 缓冲请求数据，默认值是true。通过POST或者PUT大量发送数据时，建议将此属性更改为false，以免耗尽内存。
        // clientHttpRequestFactory.setBufferRequestBody(false);

        // 添加内容转换器
        List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
        messageConverters.add(new StringHttpMessageConverter(Charset.forName("UTF-8")));
        messageConverters.add(new FormHttpMessageConverter());
        messageConverters.add(new MappingJackson2XmlHttpMessageConverter());
        messageConverters.add(new MappingJackson2HttpMessageConverter());

        restTemplate = new RestTemplate(messageConverters);
        restTemplate.setRequestFactory(clientHttpRequestFactory);
        restTemplate.setErrorHandler(new DefaultResponseErrorHandler());

        LOGGER.info("RestClient初始化完成");
    }

    private RestClient() {

    }

    @PostConstruct
    public static RestTemplate getClient() {
        return restTemplate;
    }

}
参考网页：http://blog.csdn.net/clj198606061111/article/details/70227571，http://blog.csdn.net/u010476464/article/details/50067079，http://www.cnblogs.com/winner-0715/p/6258139.html