HttpClient is a HTTP/1.1 compliant HTTP agent implementation based on HttpCore. It also provides reusable components for client-side authentication, HTTP state management, and HTTP connection management. HttpComponents Client is a successor of and replacement for Commons HttpClient 3.x. Users of Commons HttpClient are strongly encouraged to upgrade.
总结: HttpClient 是apache 组织下面的一个用于处理HTTP 请求和响应的开源工具。
需要的jar包：
? httpclient-4.3.6.jar、httpcore-4.3.3.jar、httpmime-4.3.6.jar、commons-codec-1.6.jar。
二、操作步骤
由于HttpClient从4.X开始，基本的get/post 等http请求实现方式与之前版本的写法有很大的差异，所以在此总结一下4.X版本之后的官方推荐写法。
操作顺序：
- 创建CloseableHttpClient对象
- 创建请求方法实例：HttpGet/HttpPost
- （可选）需要请求参数时
- HttpGet/HttpPost都可以使用setParams方法添加参数（deprecated 已过时）
- 对于HttpPost方法可以使用SetEntity(HttpEntity entity)参加请求参数
- 对于HttpGet方法，可以通过拼接url的方式添加请求参数
- 调用CloseableHttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个CloseableHttpResponse。
- 通过CloseableHttpResponse对象获取服务器的响应内容。
- 释放连接。无论执行方法是否成功，都必须释放连接
三、代码实例
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package com.learn.http;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
public
class {
public static void main(String[] args) {
new HttpSend().post(
"http://www.baidu.com");
new HttpSend().get(
"http://www.baidu.com");
}
/**
* 发送 post请求访问本地应用并根据传递参数不同返回不同结果
*/
public void post(String url) {
// 创建默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建httppost
HttpPost httppost =
new HttpPost(url);
// 创建参数队列
List<NameValuePair> formparams =
new ArrayList<NameValuePair>();
// 添加参数
// formparams.add(new BasicNameValuePair("gg", "1"));
UrlEncodedFormEntity uefEntity;
try {
//传入空参数，创建实体对象
uefEntity =
new UrlEncodedFormEntity(formparams,
"UTF-8");
//设置post对象的实体对象
httppost.setEntity(uefEntity);
System.out.println(
"executing post request " + httppost.getURI());
//执行post请求
CloseableHttpResponse response = httpclient.execute(httppost);
try {
//获取请求结果对象
HttpEntity entity = response.getEntity();
if (entity !=
null) {
System.out.println(
"--------------------------------------");
System.out.println(
"Response content: " + EntityUtils.toString(entity));
System.out.println(
"--------------------------------------");
}
}
finally {
response.close();
}
}
catch (ClientProtocolException e) {
e.printStackTrace();
}
catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
finally {
// 关闭连接,释放资源
try {
httpclient.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 发送 get请求
*/
public void get(String url) {
// 创建默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
// 封装请求参数
List<NameValuePair> params =
new ArrayList<>();
params.add(
new BasicNameValuePair(
"cityEname",
"henan"));
//转换为键值对
String str = EntityUtils.toString(
new UrlEncodedFormEntity(params,
"UTF-8"));
System.out.println(str);
//创建带参数get请求（示例）
HttpGet httpGet =
new HttpGet(url+
"?"+str);
// 创建不带参数get请求
HttpGet httpget =
new HttpGet(url);
System.out.println(
"executing get request " + httpget.getURI());
// 执行get请求.
CloseableHttpResponse response = httpclient.execute(httpget);
try {
// 获取响应实体
HttpEntity entity = response.getEntity();
System.out.println(
"--------------------------------------");
// 打印响应状态
System.out.println(response.getStatusLine());
if (entity !=
null) {
// 打印响应内容长度
System.out.println(
"Response content length: " + entity.getContentLength());
// 打印响应内容
System.out.println(
"Response content: " + EntityUtils.toString(entity));
}
System.out.println(
"------------------------------------");
}
finally {
response.close();
}
}
catch (ClientProtocolException e) {
e.printStackTrace();
}
catch (ParseException e) {
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
finally {
// 关闭连接,释放资源
try {
httpclient.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
}
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