java常见的http请求库有httpclient，RestTemplate，OKhttp，更高层次封装的 feign、retrofit
1、HttpClient
HttpClient：代码复杂，还得操心资源回收等。代码很复杂，冗余代码多，不建议直接使用。
2、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
package com.itunion.config;
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；
3、okhttp
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);
privatestatic 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;
}
}