1.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
2.主要的功能
（1）实现了所有 HTTP 的方法（GET,POST,PUT,DELETE 等）
（2）支持自动转向
（3）支持 HTTPS 协议
（4）支持代理服务器等
我们所用的solrj就封装了HttpClient
可用于调用微信接口
3.get请求
//1 创建Httpclient对象------------------相当于打开浏览器
CloseableHttpClient httpclient = HttpClients.createDefault();

//2 创建http GET请求--------------------在浏览器输入uri
HttpGet httpGet = new HttpGet("http://www.baidu.com/");

CloseableHttpResponse response = null;
try {
// 3执行请求-----------enter键发送请求
response = httpclient.execute(httpGet);
//4 判断返回状态是否为200----------------返回成功状态码，获取内容
if (response.getStatusLine().getStatusCode() == 200) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println("内容长度："+content.length());
}
} finally {
if (response != null) {
//5释放资源---------------------------关闭浏览器
response.close();
}
httpclient.close();
}
4.带参数的GET请求
// 定义请求的参数
URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();
// 创建http GET请求
HttpGet httpGet = new HttpGet(uri);
5.POST请求（与get请求相同，只需吧请求改为post即可）
// 创建http POST请求
HttpPost httpPost = new HttpPost("http://www.oschina.net/");
6.带参数的POST请求（设置form表单实体，表单需要参数，参数可以多个）
// 设置2个post参数，
List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
parameters.add(new BasicNameValuePair("scope", "project"));
parameters.add(new BasicNameValuePair("q", "java"));
// 构造一个form表单式的实体
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters,"UTF-8");
// 将请求实体设置到httpPost对象中
httpPost.setEntity(formEntity);
4. 使用HttpClient调用接口
1. 编写返回对象
public class HttpResult
// 响应的状态码
private int code;

// 响应的响应体
private String body;
2. 封装HttpClient常用方法
1. // 每个方法都会用到，提取出来
private CloseableHttpClient httpClient;

public ApiService() {
this.httpClient = HttpClients.createDefault();
}
2.带参数的get请求
public HttpResult doGet(String url, Map<String, Object> map) throws Exception {
// 1.创建URIBuilder
URIBuilder uriBuilder = new URIBuilder(url);

// 2.设置请求参数
if (map != null) {
// 遍历请求参数
for (Map.Entry<String, Object> entry : map.entrySet()) {
// 封装请求参数
uriBuilder.setParameter(entry.getKey(), entry.getValue().toString());
}
}

// 3.创建请求对象httpGet
HttpGet httpGet = new HttpGet(uriBuilder.build());

// 4.使用httpClient发起请求
CloseableHttpResponse response = this.httpClient.execute(httpGet);

// 5.解析返回结果，封装返回对象httpResult
// 5.1获取状态码
int code = response.getStatusLine().getStatusCode();

// 5.2 获取响应体
// 使用EntityUtils.toString方法必须保证entity不为空
String body = "";
if (response.getEntity() != null) {
body = EntityUtils.toString(response.getEntity(), "UTF-8");
}
HttpResult result = new HttpResult();
result.setCode(code);
result.setBody(body);
return result;
}
3.不带参数的get
public HttpResult doGet(String uri) throws Exception {
return this.doGet(uri, null);
}

4.带参数的post请求
//1、创建POST请求方式
HttpPost httpPost = new HttpPost(url);
//2、设置参数
List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
if(map != null){
for (Map.Entry<String, Object> m : map.entrySet()) {
parameters.add(new BasicNameValuePair(m.getKey(), m.getValue().toString()));
}
}
//3、把参数设置成form表单的形式
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters,"UTF-8");
//4、把表单对象设置到HTTPPOST请求中
httpPost.setEntity(formEntity);
//5、执行，返回响应
CloseableHttpResponse response = this.httpClient.execute(httpPost);
//6、根据响应获取状态码和数据
int code = response.getStatusLine().getStatusCode();
String body = "";
if(response.getEntity() != null){
body = EntityUtils.toString(response.getEntity(), "utf-8");
}
//7、封装返回对象
HttpResult result = new HttpResult();
result.setCode(code);
result.setBody(body);

return result;

5.不带参数的post请求
public HttpResult doPost(String url) throws Exception {
return this.doPost(url, null);
}
6.put方法和post方法类似，只需把post请求改为put请求即可
delete方法和get方法类似，只需吧get请求改为delete请求即可