Java--HttpClient請求

Java–HttpClient

HttpClient 是 Apache Jakarta Common 下的子項目，用來提供高效的、最新的、功能豐富的支持 HTTP 協議的客戶端編程工具包，並且它支持 HTTP 協議最新的版本和建議。

通過HttpClient可以模擬發出http請求，支持各種請求如get\post\delete等http協議。

也可以做爬蟲。

使用Get請求測試一下：

HttpGet請求

通過Get請求獲取到響應回來的響應體數據

public void test() throws Exception{
    	//創建一個客戶端
        CloseableHttpClient client = HttpClients.createDefault();
		//創建一個Get請求
        HttpGet httpGet = new HttpGet("http://jsonplaceholder.typicode.com/users");
		
    	//通過客戶端執行該請求，返回一個響應
        CloseableHttpResponse response = client.execute(httpGet);
		
    	//獲取響應體對象
        HttpEntity entity = response.getEntity();
    	
    	//獲取響應體內容
        InputStream content = entity.getContent();
        byte[] bytes=new byte[102400];
        int read = content.read(bytes);

    	//輸出到控制檯
        System.out.println(new String(bytes,0,read));
    
    	//關閉掉所有流
        content.close();
        response.close();
        client.close();
    }


//響應回來的Json數據

[
  {
    "id": 1,
    "name": "Leanne Graham",
    "username": "Bret",
    "email": "[email protected]",
    "address": {
      "street": "Kulas Light",
      "suite": "Apt. 556",
      "city": "Gwenborough",
      "zipcode": "92998-3874",
      "geo": {
        "lat": "-37.3159",
        "lng": "81.1496"
      }

  

各種請求都是繼承自HttpRequestBase,HttpRequestBase再向上繼承。

基本上只是方法名字不同。

@NotThreadSafe
public class HttpGet extends HttpRequestBase {

    public final static String METHOD_NAME = "GET";

    public HttpGet() {
        super();
    }

    public HttpGet(final URI uri) {
        super();
        setURI(uri);
    }

    /**
     * @throws IllegalArgumentException if the uri is invalid.
     */
    public HttpGet(final String uri) {
        super();
        setURI(URI.create(uri));
    }

    @Override
    public String getMethod() {
        return METHOD_NAME;
    }

}

爬蟲

HttpClient也可以用於爬蟲，如：

將獲取的網絡資源輸出到文件中。

//傳入url，以及資源路徑
public static void getUrl(String url,String path) throws Exception{
        CloseableHttpClient client = HttpClients.createDefault();

        HttpGet httpGet = new HttpGet(url);

        CloseableHttpResponse response = client.execute(httpGet);

        HttpEntity entity = response.getEntity();
        InputStream inputStream = entity.getContent();
	
    	//打印流
        PrintStream printStream=new PrintStream(path);
        int len;

        while((len=inputStream.read())!=-1){
            printStream.write(len);
        }

        inputStream.close();
        printStream.close();
        response.close();
        client.close();

    }

    @Test
    public void test2() throws Exception{
        getUrl("http://jsonplaceholder.typicode.com/users","./get.json");
    }