HttpClient配置及運用（一）

　　HttpComponents是Apache 旗下的項目。其中有一個HttpClient，即HTTP客戶端。

之后我們建立項目，導入jar包，開始開發

　　一、獲取網頁內容:

package com.zhi.httpClient;
 
import java.io.IOException;
 
import org.apache.http.HttpEntity;
import org.apache.http.ParseException;
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;
import org.apache.http.util.EntityUtils;
 
public class Demo {
    public static void main(String[] args) {
        CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、創建實例
        //CloseableHttpClient意思是：可關閉的
        HttpGet httpGet=new HttpGet("http://www.huimsoft.com"); //2、創建實例
         
        //限制類型http://www.tuicool.com/
         
        CloseableHttpResponse closeableHttpResponse=null;
        try {
            closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、執行
        } catch (ClientProtocolException e) { //客戶端協議異常
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) { //IO異常
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、獲取實體
 
        String str="";
        try {
            str=EntityUtils.toString(httpEntity, "utf-8"); //獲取網頁內容，並且指定編碼
        } catch (ParseException e) { //解析異常
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println(str);
         
        //關閉closeableHttpResponse
        try {
            closeableHttpResponse.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         
        //關閉closeableHttpClient
        try {
            closeableHttpClient.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

　　代碼有很多，但是很多是在處理異常，所以我們也可以使用throws在方法上拋出，以簡化代碼格式，讓其更好看。

　　

package com.zhi.httpClient;
 
import org.apache.http.HttpEntity;
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;
import org.apache.http.util.EntityUtils;
 
public class Test {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、創建實例
        HttpGet httpGet=new HttpGet("http://www.huimsoft.com"); //2、創建請求
         
        CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、執行
        HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、獲取實體
        System.out.println(EntityUtils.toString(httpEntity, "utf-8")); //5、獲取網頁內容，並且指定編碼
         
        closeableHttpResponse.close();
        closeableHttpClient.close();
    }
}

  二、設置請求頭信息

　設置請求頭信息的目的是為了模擬瀏覽器

　　

package com.zhi.httpClient2;
 
import org.apache.http.HttpEntity;
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;
import org.apache.http.util.EntityUtils;
 
public class Demo {
 
    public static void main(String[] args) throws Exception {
        CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、創建實例
        HttpGet httpGet=new HttpGet("http://www.tuicool.com"); //2、創建請求
         
        httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36 SE 2.X MetaSr 1.0");
         
        CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、執行
        HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、獲取實體
        System.out.println(EntityUtils.toString(httpEntity, "utf-8")); //5、獲取網頁內容，並且指定編碼
         
        closeableHttpResponse.close();
        closeableHttpClient.close();
    }
 
}

三、獲取相應頭信息Response　Headers的內容類型Content-type

package com.zhi.httpClient2;
 
import org.apache.http.Header;
import org.apache.http.HttpEntity;
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 Demo {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、創建實例
        HttpGet httpGet=new HttpGet("http://www.tuicool.com"); //2、創建請求
         
        httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36 SE 2.X MetaSr 1.0");
         
        CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、執行
        HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、獲取實體
         
        Header header=httpEntity.getContentType();
        System.out.println(header.toString()); //獲取頭信息內容
        System.out.println(header.getName().toString()); //這是獲取key
        System.out.println(header.getValue().toString()); //這是獲取value
         
        //System.out.println(EntityUtils.toString(httpEntity, "utf-8")); //5、獲取網頁內容，並且指定編碼
        closeableHttpResponse.close();
        closeableHttpClient.close();
    }
}

運行輸出：

Content-Type: text/html; charset=utf-8
Content-Type
text/html; charset=utf-8

我們的重點是獲取的value的值，有些是text/html的，有些是其他的，比如我們請求一個js文件。

https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js

　

HttpGet httpGet=new HttpGet("http://cdn.bootcss.com/jquery/1.12.4/jquery.min.js");

public class Demo {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、創建實例
        HttpGet httpGet=new HttpGet("http://cdn.bootcss.com/jquery/1.12.4/jquery.min.js"); //2、創建實例
         
        httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36 SE 2.X MetaSr 1.0");
         
        CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、執行
        HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、獲取實體
         
        Header header=httpEntity.getContentType();
        System.out.println(header.getValue().toString()); //這是獲取value
         
        closeableHttpResponse.close();
        closeableHttpClient.close();
    }
}

運行結果：

運行結果：application/javascript

如果請求一個圖片，同上

運行結果：image/png