Oracle 索引

使用HttpClient进行网络处理的基本步骤如下：

1、通过get的方式获取到Response对象。

CloseableHttpClient httpClient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet("http://www.baidu.com/");
CloseableHttpResponse response = httpClient.execute(httpGet);

2、获取Response对象的Entity。

HttpEntity entity = response.getEntity();

注：HttpClient将Response的正文及Request的POST/PUT方法中的正文均封装成一个HttpEntity对象。可以通过entity.getContenType()，entity.getContentLength()等方法获取到正文的相关信息。但最重要的方法是通过getContent()获取到InputStream对象。

3、通过Entity获取到InputStream对象，然后对返回内容进行处理。

is = entity.getContent();
sc = new Scanner(is);
// String filename = path.substring(path.lastIndexOf(‘/‘)+1);
String filename = "2.txt";
os = new PrintWriter(filename);
while (sc.hasNext()) {
	os.write(sc.nextLine());
}

使用HtppClient下载一个网页的完整代码如下：

package com.ljh.test;

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.Scanner;

import org.apache.http.HttpEntity;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

public class DownloadWebPage{

	public static void downloadPagebyGetMethod() throws IOException {

		// 1、通过HttpGet获取到response对象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		HttpGet httpGet = new HttpGet("http://www.baidu.com/");
		CloseableHttpResponse response = httpClient.execute(httpGet);

		InputStream is = null;
		Scanner sc = null;
		Writer os = null;
		if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
			try {
				// 2、获取response的entity。
				HttpEntity entity = response.getEntity();

				// 3、获取到InputStream对象，并对内容进行处理
				is = entity.getContent();
				sc = new Scanner(is);
				// String filename = path.substring(path.lastIndexOf(‘/‘)+1);
				String filename = "2.txt";
				os = new PrintWriter(filename);
				while (sc.hasNext()) {
					os.write(sc.nextLine());
				}

			} catch (ClientProtocolException e) {
				e.printStackTrace();
			} finally {
				if (sc != null) {
					sc.close();
				}
				if (is != null) {
					is.close();
				}
				if (os != null) {
					os.close();
				}
				if (response != null) {
					response.close();
				}
			}
		}

	}

	public static void main(String[] args) {
		try {
			downloadPagebyGetMethod();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

注意：直接将HttpGet改为HttpPost，返回的结果有误，百度返回302状态，即重定向，新浪返回拒绝访问。怀疑大多网站均不允许POST方法直接访问网站。

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