java常见的http请求库

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1.HttpURLConnection

优点：HttpURLConnection是一种多用途、轻量极的HTTP客户端，使用它来进行HTTP操作可以适用于大多数的应用程序。虽然HttpURLConnection的API提供的比较简单，但是同时这也使得我们可以更加容易地去使用和扩展它。比较轻便，灵活，易于扩展。

缺点：HttpURLConnection是java的标准类，什么都没封装，用起来太原始，不方便，比如重访问的自定义，以及一些高级功能等。 在android 2.2及以下版本中HttpUrlConnection存在着一些bug，所以建议在android2.3以后使用HttpUrlConnection，2.3之前使用HttpClient。

private static String getResult(String urlStr, String content, String encoding) {
	URL url = null;
	HttpURLConnection connection = null;
	try {
		url = new URL(urlStr);
		connection = (HttpURLConnection) url.openConnection();// 新建连接实例
		connection.setConnectTimeout(1000);// 设置连接超时时间，单位毫秒
		connection.setReadTimeout(1000);// 设置读取数据超时时间，单位毫秒
		connection.setDoOutput(true);// 是否打开输出流 true|false
		connection.setDoInput(true);// 是否打开输入流true|false
		connection.setRequestMethod("POST");// 提交方法POST|GET
		connection.setUseCaches(false);// 是否缓存true|false
		connection.connect();// 打开连接端口
		DataOutputStream out = new DataOutputStream(connection
				.getOutputStream());// 打开输出流往对端服务器写数据
		out.writeBytes(content);// 写数据,也就是提交你的表单 name=xxx&pwd=xxx
		out.flush();// 刷新
		out.close();// 关闭输出流
		BufferedReader reader = new BufferedReader(new InputStreamReader(
				connection.getInputStream(), encoding));// 往对端写完数据对端服务器返回数据
		// ,以BufferedReader流来读取
		StringBuffer buffer = new StringBuffer();
		String line = "";
		while ((line = reader.readLine()) != null) {
			buffer.append(line);
		}
		reader.close();
		return buffer.toString();
	} catch (IOException e) {
		e.printStackTrace();
	} finally {
		if (connection != null) {
			connection.disconnect();// 关闭连接
		}
	}
	return null;
}

2.HttpClient

优点：apache httpclient高效稳定，有很多API

缺点：由于API太多，很难在不破坏兼容性的情况下对它进行升级和扩展，维护成本高，故android 开发团队不愿意在维护该库而是转投更为轻便的httpurlconnection。Apache HttpClient早就不推荐httpclient，5.0之后干脆废弃，后续会删除。6.0删除了HttpClient。Java开发用HttpClient，官方推荐Android开发用HttpUrlConnection。

1.post常用方式

public static String sendPost(String memberId,String params, String requestUrl,
                                  String authorization) throws Exception {

    String result;
    InputStream inputStream=null,soapResponseStream =null;
    PostMethod postMethod =null;
	try {
		HttpClient httpClient = new HttpClient(new MultiThreadedHttpConnectionManager());// 客户端实例化
		byte[] requestBytes = params.getBytes("utf-8"); // 将参数转为二进制流
		postMethod = new PostMethod(requestUrl);
		//设置请求头Authorization
		postMethod.setRequestHeader("Authorization", "Basic " + authorization);
		// 设置请求头  Content-Type
	 	postMethod.setRequestHeader("Content-Type", "application/json");
		 //请求头信息中添加关闭连接
		postMethod.addRequestHeader("Connection", "close");
		inputStream = new ByteArrayInputStream(requestBytes, 0,
		        requestBytes.length);
		RequestEntity requestEntity = new InputStreamRequestEntity(inputStream,
		        requestBytes.length, "application/json; charset=utf-8"); // 请求体
		postMethod.setRequestEntity(requestEntity);
		httpClient.executeMethod(postMethod);// 执行请求
		soapResponseStream = postMethod.getResponseBodyAsStream();// 获取返回的流
		byte[] datas = readInputStream(soapResponseStream);// 从输入流中读取数据
		//连发三次机制
	    httpClient.getParams().setBooleanParameter("http.protocol.expect-continue", false);
		result = new String(datas, "UTF-8");
	} catch (Exception e) {
		throw new Exception(e);
	}finally {
		//释放连接
		if(postMethod!=null){
			postMethod.releaseConnection();
		}
    }
    return result;

}

2.带连接池的post调用

//整个连接池的最大连接数默认是20，连接池的每个路由的最大连接数默认是2，可设置超时,可设置重试
public static String doPost(String url, String data) throws Exception {
    StringBuilder result = new StringBuilder();
    CloseableHttpClient httpclient = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost(url);

    try {
    	logger.info("executing request" + httpPost.getRequestLine());
    	if (StringUtils.isNotBlank(data)) {
    		httpPost.setEntity(new StringEntity(data, "UTF-8"));
    	}
    	CloseableHttpResponse response = httpclient.execute(httpPost);
    	try {
    		HttpEntity entity = response.getEntity();
    		logger.info(response.getStatusLine());
    		if (entity != null) {
    			System.out.println("Response content length: " + entity.getContentLength());
    			BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(entity.getContent(), "UTF-8"));
    			String text;
    			while ((text = bufferedReader.readLine()) != null) {
    				result.append(text);
    			}
    		}
    		EntityUtils.consume(entity);
    	} catch (Exception e) {
    		logger.error(e, e);
    	} finally {
    		response.getEntity().getContent().close();
    		response.close();
    		httpPost.releaseConnection();
    	}
    } finally {
    	httpclient.close();
    }
    return result.toString();
    }

3.RestTemplate

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。

引入jar包：

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

添加初始化配置（也可以不配，有默认的）–注意RestTemplate只有初始化配置，没有什么连接池

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.web.client.RestTemplate;

@Configuration
public class ApiConfig {
    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        return new RestTemplate(factory);
    }

    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();//默认的是JDK提供http连接，需要的话可以//通过setRequestFactory方法替换为例如Apache HttpComponents、Netty或//OkHttp等其它HTTP library。
        factory.setReadTimeout(5000);//单位为ms
        factory.setConnectTimeout(5000);//单位为ms
        return factory;
    }
}

(1）get请求（不带参的即把参数取消即可）

// 1-getForObject()
User user1 = this.restTemplate.getForObject(uri, User.class);

// 2-getForEntity()
ResponseEntity<User> responseEntity1 = this.restTemplate.getForEntity(uri, User.class);
HttpStatus statusCode = responseEntity1.getStatusCode();
HttpHeaders header = responseEntity1.getHeaders();
User user2 = responseEntity1.getBody();

// 3-exchange()
RequestEntity requestEntity = RequestEntity.get(new URI(uri)).build();
ResponseEntity<User> responseEntity2 = this.restTemplate.exchange(requestEntity, User.class);
User user3 = responseEntity2.getBody();

方式一： ``` Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/{1}/{2}"
            , Notice.class,1,5); ```
方式二： ``` Map<String,String> map = new HashMap();
    map.put("start","1");
    map.put("page","5");
    Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/"
            , Notice.class,map); ```

(2）post请求：

// 1-postForObject()
User user1 = this.restTemplate.postForObject(uri, user, User.class);

// 2-postForEntity()
ResponseEntity<User> responseEntity1 = this.restTemplate.postForEntity(uri, user, User.class);

// 3-exchange()
RequestEntity<User> requestEntity = RequestEntity.post(new URI(uri)).body(user);
ResponseEntity<User> responseEntity2 = this.restTemplate.exchange(requestEntity, User.class);

方式一：

String url = "http://demo/api/book/";
        HttpHeaders headers = new HttpHeaders();
        MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
        headers.setContentType(type);
        String requestJson = "{...}";
        HttpEntity<String> entity = new HttpEntity<String>(requestJson,headers);
        String result = restTemplate.postForObject(url, entity, String.class);
        System.out.println(result);

方式二：

@Test
public void rtPostObject(){
    RestTemplate restTemplate = new RestTemplate();
    String url = "http://47.xxx.xxx.96/register/checkEmail";
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
    MultiValueMap<String, String> map= new LinkedMultiValueMap<>();
    map.add("email", "844072586@qq.com");

    HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);
    ResponseEntity<String> response = restTemplate.postForEntity( url, request , String.class );
    System.out.println(response.getBody());
}
其它：还支持上传和下载功能；

4.okhttp

OkHttp是一个高效的HTTP客户端，允许所有同一个主机地址的请求共享同一个socket连接；连接池减少请求延时；透明的GZIP压缩减少响应数据的大小；缓存响应内容，避免一些完全重复的请求。

当网络出现问题的时候OkHttp依然坚守自己的职责，它会自动恢复一般的连接问题，如果你的服务有多个IP地址，当第一个IP请求失败时，OkHttp会交替尝试你配置的其他IP，OkHttp使用现代TLS技术(SNI, ALPN)初始化新的连接，当握手失败时会回退到TLS 1.0。

(1）使用：它的请求/响应 API 使用构造器模式builders来设计，它支持阻塞式的同步请求和带回调的异步请求。

引入jar包：

<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>3.10.0</version>
</dependency>

(2）配置文件：

import okhttp3.ConnectionPool;
import okhttp3.OkHttpClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeUnit;

@Configuration
public class OkHttpConfiguration {

    @Bean
    public OkHttpClient okHttpClient() {
        return new OkHttpClient.Builder()
                //.sslSocketFactory(sslSocketFactory(), x509TrustManager())
                .retryOnConnectionFailure(false)
                .connectionPool(pool())
                .connectTimeout(30, TimeUnit.SECONDS)
                .readTimeout(30, TimeUnit.SECONDS)
                .writeTimeout(30,TimeUnit.SECONDS)
                .build();
    }

    @Bean
    public X509TrustManager x509TrustManager() {
        return new X509TrustManager() {
            @Override
            public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
            }
            @Override
            public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
            }
            @Override
            public X509Certificate[] getAcceptedIssuers() {
                return new X509Certificate[0];
            }
        };
    }

    @Bean
    public SSLSocketFactory sslSocketFactory() {
        try {
            //信任任何链接
            SSLContext sslContext = SSLContext.getInstance("TLS");
            sslContext.init(null, new TrustManager[]{x509TrustManager()}, new SecureRandom());
            return sslContext.getSocketFactory();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * Create a new connection pool with tuning parameters appropriate for a single-user application.
     * The tuning parameters in this pool are subject to change in future OkHttp releases. Currently
     */
    @Bean
    public ConnectionPool pool() {
        return new ConnectionPool(200, 5, TimeUnit.MINUTES);
    }
}

(3）util工具：

import okhttp3.*;
import org.apache.commons.lang3.exception.ExceptionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.util.Iterator;
import java.util.Map;

public class OkHttpUtil{
    private static final Logger logger = LoggerFactory.getLogger(OkHttpUtil.class);

    private static OkHttpClient  okHttpClient;

    @Autowired
    public OkHttpUtil(OkHttpClient  okHttpClient) {
        OkHttpUtil.okHttpClient= okHttpClient;
    }

    /**
     * get
     * @param url     请求的url
     * @param queries 请求的参数，在浏览器？后面的数据，没有可以传null
     * @return
     */
    public static  String get(String url, Map<String, String> queries) {
        String responseBody = "";
        StringBuffer sb = new StringBuffer(url);
        if (queries != null && queries.keySet().size() > 0) {
            boolean firstFlag = true;
            Iterator iterator = queries.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry entry = (Map.Entry<String, String>) iterator.next();
                if (firstFlag) {
                    sb.append("?" + entry.getKey() + "=" + entry.getValue());
                    firstFlag = false;
                } else {
                    sb.append("&" + entry.getKey() + "=" + entry.getValue());
                }
            }
        }
        Request request = new Request.Builder()
                .url(sb.toString())
                .build();
        Response response = null;
        try {
            response = okHttpClient.newCall(request).execute();
            int status = response.code();
            if (response.isSuccessful()) {
                return response.body().string();
            }
        } catch (Exception e) {
            logger.error("okhttp3 put error >> ex = {}", ExceptionUtils.getStackTrace(e));
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return responseBody;
    }

    /**
     * post
     *
     * @param url    请求的url
     * @param params post form 提交的参数
     * @return
     */
    public static String post(String url, Map<String, String> params) {
        String responseBody = "";
        FormBody.Builder builder = new FormBody.Builder();
        //添加参数
        if (params != null && params.keySet().size() > 0) {
            for (String key : params.keySet()) {
                builder.add(key, params.get(key));
            }
        }
        Request request = new Request.Builder()
                .url(url)
                .post(builder.build())
                .build();
        Response response = null;
        try {
            response = okHttpClient.newCall(request).execute();
            int status = response.code();
            if (response.isSuccessful()) {
                return response.body().string();
            }
        } catch (Exception e) {
            logger.error("okhttp3 post error >> ex = {}", ExceptionUtils.getStackTrace(e));
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return responseBody;
    }

    /**
     * get
     * @param url     请求的url
     * @param queries 请求的参数，在浏览器？后面的数据，没有可以传null
     * @return
     */
    public static String getForHeader(String url, Map<String, String> queries) {
        String responseBody = "";
        StringBuffer sb = new StringBuffer(url);
        if (queries != null && queries.keySet().size() > 0) {
            boolean firstFlag = true;
            Iterator iterator = queries.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry entry = (Map.Entry<String, String>) iterator.next();
                if (firstFlag) {
                    sb.append("?" + entry.getKey() + "=" + entry.getValue());
                    firstFlag = false;
                } else {
                    sb.append("&" + entry.getKey() + "=" + entry.getValue());
                }
            }
        }
        Request request = new Request.Builder()
                .addHeader("key", "value")
                .url(sb.toString())
                .build();
        Response response = null;
        try {
            response = okHttpClient.newCall(request).execute();
            int status = response.code();
            if (response.isSuccessful()) {
                return response.body().string();
            }
        } catch (Exception e) {
            logger.error("okhttp3 put error >> ex = {}", ExceptionUtils.getStackTrace(e));
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return responseBody;
    }

    /**
     * Post请求发送JSON数据....{"name":"zhangsan","pwd":"123456"}
     * 参数一：请求Url
     * 参数二：请求的JSON
     * 参数三：请求回调
     */
    public static String postJsonParams(String url, String jsonParams) {
        String responseBody = "";
        RequestBody requestBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), jsonParams);
        Request request = new Request.Builder()
                .url(url)
                .post(requestBody)
                .build();
        Response response = null;
        try {
            response = okHttpClient.newCall(request).execute();
            int status = response.code();
            if (response.isSuccessful()) {
                return response.body().string();
            }
        } catch (Exception e) {
            logger.error("okhttp3 post error >> ex = {}", ExceptionUtils.getStackTrace(e));
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return responseBody;
    }

    /**
     * Post请求发送xml数据....
     * 参数一：请求Url
     * 参数二：请求的xmlString
     * 参数三：请求回调
     */
    public static String postXmlParams(String url, String xml) {
        String responseBody = "";
        RequestBody requestBody = RequestBody.create(MediaType.parse("application/xml; charset=utf-8"), xml);
        Request request = new Request.Builder()
                .url(url)
                .post(requestBody)
                .build();
        Response response = null;
        try {
            response = okHttpClient.newCall(request).execute();
            int status = response.code();
            if (response.isSuccessful()) {
                return response.body().string();
            }
        } catch (Exception e) {
            logger.error("okhttp3 post error >> ex = {}", ExceptionUtils.getStackTrace(e));
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return responseBody;
    }
}

参考资料

  1. java常见的 http 请求库比较
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