目录
一、介绍
HttpClient 是Apache Jakarta Common 下的子项目，可以用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。
HttpClient作用：
发送HTTP请求
接收响应数据
为什么要在Java程序中发送Http请求？有哪些应用场景呢？
HttpClient应用场景：
当我们在使用扫描支付、查看地图、获取验证码、查看天气等功能时
其实，应用程序本身并未实现这些功能，都是在应用程序里访问提供这些功能的服务，访问这些服务需要发送HTTP请求，并且接收响应数据，可通过HttpClient来实现。
HttpClient的maven坐标：
<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.13</version> </dependency>HttpClient的核心API：
HttpClient：Http客户端对象类型，使用该类型对象可发起Http请求。
HttpClients：可认为是构建器，可创建HttpClient对象。
CloseableHttpClient：实现类，实现了HttpClient接口。
HttpGet：Get方式请求类型。
HttpPost：Post方式请求类型。
HttpClient发送请求步骤：
创建HttpClient对象
创建Http请求对象
调用HttpClient的execute方法发送请求
二、Get方式请求发送入门案例
首先，应该导入HttpClient相关的坐标，但在项目中，就算不导入，也可以使用相关的API。
因为在项目中已经引入了aliyun-sdk-oss坐标：
<dependency> <groupId>com.aliyun.oss</groupId> <artifactId>aliyun-sdk-oss</artifactId> </dependency>
实现步骤：
创建HttpClient对象
创建请求对象
发送请求，接受响应结果
解析结果
关闭资源
@SpringBootTest public class HttpClientTest { /** * 测试通过httpclient发送GET方式的请求 */ @Test public void testGET() throws Exception{ //创建httpclient对象 CloseableHttpClient httpClient = HttpClients.createDefault(); //创建请求对象 HttpGet httpGet = new HttpGet("http://localhost:8080/user/shop/status"); //发送请求，接受响应结果 CloseableHttpResponse response = httpClient.execute(httpGet); //获取服务端返回的状态码 int statusCode = response.getStatusLine().getStatusCode(); System.out.println("服务端返回的状态码为：" + statusCode); HttpEntity entity = response.getEntity(); String body = EntityUtils.toString(entity); System.out.println("服务端返回的数据为：" + body); //关闭资源 response.close(); httpClient.close(); } }在访问http://localhost:8080/user/shop/status请求时，需要提前启动项目
测试结果：
三、Post方式请求发送入门案例
实现步骤：
创建HttpClient对象
创建请求对象
发送请求，接收响应结果
解析响应结果
关闭资源
/** * 测试通过httpclient发送POST方式的请求 */ @Test public void testPOST() throws Exception{ // 创建httpclient对象 CloseableHttpClient httpClient = HttpClients.createDefault(); //创建请求对象 HttpPost httpPost = new HttpPost("http://localhost:8080/admin/employee/login"); JSONObject jsonObject = new JSONObject(); jsonObject.put("username","admin"); jsonObject.put("password","123456"); StringEntity entity = new StringEntity(jsonObject.toString()); //指定请求编码方式 entity.setContentEncoding("utf-8"); //数据格式 entity.setContentType("application/json"); httpPost.setEntity(entity); //发送请求 CloseableHttpResponse response = httpClient.execute(httpPost); //解析返回结果 int statusCode = response.getStatusLine().getStatusCode(); System.out.println("响应码为：" + statusCode); HttpEntity entity1 = response.getEntity(); String body = EntityUtils.toString(entity1); System.out.println("响应数据为：" + body); //关闭资源 response.close(); httpClient.close(); }
测试结果：
四、集合好的工具类
/**
* Http工具类
*/
public class HttpClientUtil {
static final int TIMEOUT_MSEC = 5 * 1000;
/**
* 发送GET方式请求
* @param url
* @param paramMap
* @return
*/
public static String doGet(String url,Map<String,String> paramMap){
// 创建Httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
String result = "";
CloseableHttpResponse response = null;
try{
URIBuilder builder = new URIBuilder(url);
if(paramMap != null){
for (String key : paramMap.keySet()) {
builder.addParameter(key,paramMap.get(key));
}
}
URI uri = builder.build();
//创建GET请求
HttpGet httpGet = new HttpGet(uri);
//发送请求
response = httpClient.execute(httpGet);
//判断响应状态
if(response.getStatusLine().getStatusCode() == 200){
result = EntityUtils.toString(response.getEntity(),"UTF-8");
}
}catch (Exception e){
e.printStackTrace();
}finally {
try {
response.close();
httpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}
/**
* 发送POST方式请求
* @param url
* @param paramMap
* @return
* @throws IOException
*/
public static String doPost(String url, Map<String, String> paramMap) throws IOException {
// 创建Httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = null;
String resultString = "";
try {
// 创建Http Post请求
HttpPost httpPost = new HttpPost(url);
// 创建参数列表
if (paramMap != null) {
List<NameValuePair> paramList = new ArrayList();
for (Map.Entry<String, String> param : paramMap.entrySet()) {
paramList.add(new BasicNameValuePair(param.getKey(), param.getValue()));
}
// 模拟表单
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
httpPost.setEntity(entity);
}
httpPost.setConfig(builderRequestConfig());
// 执行http请求
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
} catch (Exception e) {
throw e;
} finally {
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return resultString;
}
/**
* 发送POST方式请求
* @param url
* @param paramMap
* @return
* @throws IOException
*/
public static String doPost4Json(String url, Map<String, String> paramMap) throws IOException {
// 创建Httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = null;
String resultString = "";
try {
// 创建Http Post请求
HttpPost httpPost = new HttpPost(url);
if (paramMap != null) {
//构造json格式数据
JSONObject jsonObject = new JSONObject();
for (Map.Entry<String, String> param : paramMap.entrySet()) {
jsonObject.put(param.getKey(),param.getValue());
}
StringEntity entity = new StringEntity(jsonObject.toString(),"utf-8");
//设置请求编码
entity.setContentEncoding("utf-8");
//设置数据类型
entity.setContentType("application/json");
httpPost.setEntity(entity);
}
httpPost.setConfig(builderRequestConfig());
// 执行http请求
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
} catch (Exception e) {
throw e;
} finally {
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return resultString;
}
private static RequestConfig builderRequestConfig() {
return RequestConfig.custom()
.setConnectTimeout(TIMEOUT_MSEC)
.setConnectionRequestTimeout(TIMEOUT_MSEC)
.setSocketTimeout(TIMEOUT_MSEC).build();
}
}