2019独角兽企业重金招聘Python工程师标准>>> 
三个简单的HTTPClient4.3小例子
写三个httpclient的小例子，希望对刚开始学习httpclient的小伙伴们有一个参考↖(^ω^)↗
1、简单的获取一个HTML页面的内容
public void getHTML() throws Exception {
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet("http://www.baidu.com/");
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
String html = EntityUtils.toString(entity);
httpclient.close();
}2、下载一个图片到本地
public class DownloadFile {
public static void main(String[] args) throws Exception {
//图片的网址
String url = "http://ww2.sinaimg.cn/large/9d57a855jw1dqpv9fp4yuj.jpg";
String destfilename = "D:\\TDDOWNLOAD\\cat.jpg";
//生成一个httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpget = new HttpGet(url);
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
InputStream in = entity.getContent();
File file = new File(destfilename);
try {
FileOutputStream fout = new FileOutputStream(file);
int l = -1;
byte[] tmp = new byte[1024];
while ((l = in.read(tmp)) != -1) {
fout.write(tmp,0,l);
//注意这里如果用OutputStream.write(buff)的话，图片会失真，大家可以试试
}
fout.flush();
fout.close();
} finally {
// 关闭低层流。
in.close();
}
httpclient.close();
}
}3.post模拟人人网登陆
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
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 LoginRR {
private CloseableHttpClient httpclient;
private HttpPost httppost;//用于提交登陆数据
private HttpGet httpget;//用于获得登录后的页面
private String login_success;//用于构造上面的HttpGet
public LoginRR()
{
httpclient = HttpClients.createDefault();
//人人的登陆界面网址
httppost = new HttpPost("http://www.renren.com/PLogin.do");
}
public void logIn(String name, String password) throws Exception
{
//打包将要传入的参数
List params = new ArrayList();
params.add(new BasicNameValuePair("email", name));
params.add(new BasicNameValuePair("password",password));
httppost.setEntity(new UrlEncodedFormEntity(params));
try {
//提交登录数据
HttpResponse re = httpclient.execute(httppost);
//获得跳转的网址
Header locationHeader = re.getFirstHeader("Location");
//登陆不成功
if (locationHeader == null)
{
System.out.println("登陆不成功，请稍后再试!");
return;
}
else//成功
{
login_success=locationHeader.getValue();//获取登陆成功之后跳转链接
System.out.println("成功之后跳转到的网页网址："+login_success);
}
}catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void PrintText() throws IOException
{
httpget = new HttpGet(login_success);
HttpResponse re2 = null;
try {
re2 = httpclient.execute(httpget);
//输出登录成功后的页面
String str=EntityUtils.toString(re2.getEntity());
System.out.println(str);
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally
{
httppost.abort();
httpget.abort();
httpclient.close();
}
}
public static void main(String[] args) throws Exception
{
String name = "username", password = "password ";
//自己的账号，口令
LoginRR lr = new LoginRR();
lr.logIn(name, password);
lr.PrintText();
}
}