HttpClient 4 API –获取状态代码-getStatusLine（）。getStatusCode（）示例

╰+哭是因爲堅強的太久メ 2023-02-25 03:58 14阅读 0赞

在HttpClient API中获取状态代码的快速指南。 getStatusLine（）。getStatusCode（）示例和相关的错误。

## 1.简介 ##

在这个非常快速的教程中，我将展示如何使用HttpClient 4获取和验证HTTP响应的StatusCode。

## 2. Maven依赖 ##

要运行此HttiClient应用程序，需要以下jar。

commons-logging在内部被其他jar使用。 请不要忘记添加这些jar，否则您将获得编译时和运行时错误。

<dependency>
        <groupId>commons-logging</groupId>
        <artifactId>commons-logging</artifactId>
        <version>1.2</version>
    </dependency>
    
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.12</version>
    </dependency>
    
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpcore</artifactId>
        <version>4.4.13</version>
    </dependency>

**错误：**

如果您错过了commons-logging jar，则会产生以下异常。

Exception in thread "main" Exception in thread java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory 
      at org.apache.http.conn.ssl.DefaultHostnameVerifier.<init>(DefaultHostnameVerifier.java: 82 ) 
      at org.apache.http.impl.client.HttpClientBuilder.build(HttpClientBuilder.java: 966 ) 
      at com.java.w3schools.blog.HttpClient.HttpClientGetStatusCode.main(HttpClientGetStatusCode.java: 21 )  Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory 
      at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java: 583 ) 
      at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java: 178 ) 
      at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java: 521 ) 
      ... 3 more

## 3.从Http响应中检索状态代码 ##

发送HTTP请求后，经过处理后，响应将发送回调用方。

package com.java.w3schools.blog.HttpClient;  import java.io.IOException;  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.HttpClientBuilder;  public class HttpClientGetStatusCode { 
      private static final String GOOGLE_URL = " http://www.google.com " ; 
      private static CloseableHttpClient instance; 
      private static CloseableHttpResponse response; 
      public static void main(String[] args) throws ClientProtocolException, IOException { 
       HttpGet httpGet = new HttpGet(GOOGLE_URL); 
       instance = HttpClientBuilder.create().build(); 
       response = instance.execute(httpGet); 
       System.out.println( "response.getStatusLine() :: " + response.getStatusLine()); 
       final int statusCode = response.getStatusLine().getStatusCode(); 
       int code = HttpStatus.SC_OK; 
       if (code == statusCode) { 
        System.out.println( "Status Code : " + code); 
       } else { 
        System.out.println( "StatusCode not 200 : " + code); 
       } 
      }  }

返回的响应类型为*org.apache.http.HttpResponse* ，它使我们能够获取请求的执行状态。 *getStatusLine（）*方法返回保存请求状态的StatusLine对象。 用  
*getStatusCode（）*仅获取执行代码。

**输出：**

response.getStatusLine() :: HTTP/ 1.1 200 OK  Status Code : 200

## 4. URL断开时例外 ##

如果给定的URL关闭或错误，则我们将获得*[UnknownHostException][]*运行时异常。

Exception in thread "main" Exception in thread java.net.UnknownHostException: www.google.com1: nodename nor servname provided, or not known 
      at java.base/java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) 
      at java.base/java.net.InetAddress$PlatformNameService.lookupAllHostAddr(InetAddress.java: 929 ) 
      at java.base/java.net.InetAddress.getAddressesFromNameService(InetAddress.java: 1515 ) 
      at java.base/java.net.InetAddress$NameServiceAddresses.get(InetAddress.java: 848 ) 
      at java.base/java.net.InetAddress.getAllByName0(InetAddress.java: 1505 ) 
      at java.base/java.net.InetAddress.getAllByName(InetAddress.java: 1364 ) 
      at java.base/java.net.InetAddress.getAllByName(InetAddress.java: 1298 ) 
      at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java: 45 ) 
      at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java: 112 ) 
      at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java: 376 ) 
      at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java: 393 ) 
      at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java: 236 ) 
      at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java: 186 ) 
      at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java: 89 ) 
      at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java: 110 ) 
      at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java: 185 ) 
      at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java: 83 ) 
      at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java: 108 ) 
      at com.java.w3schools.blog.HttpClient.HttpClientGetStatusCode.main(HttpClientGetStatusCode.java: 24 )

## 5.结论 ##

在本文中，我们已经看到了**如何获取HttpClient**请求**的状态代码** 。

与往常一样，本文显示的示例在Github上。

**[GitHub代码][GitHub]**

> 翻译自: [https://www.javacodegeeks.com/2020/04/httpclient-4-api-get-the-status-code-getstatusline-getstatuscode-example.html][https_www.javacodegeeks.com_2020_04_httpclient-4-api-get-the-status-code-getstatusline-getstatuscode-example.html]

[UnknownHostException]: https://docs.oracle.com/javase/8/docs/api/java/rmi/UnknownHostException.html
[GitHub]: https://github.com/java-w3schools/Tutorials/blob/master/CoreJava/src/main/java/com/java/w3schools/blog/HttpClient/HttpClientGetStatusCode.java
[https_www.javacodegeeks.com_2020_04_httpclient-4-api-get-the-status-code-getstatusline-getstatuscode-example.html]: https://www.javacodegeeks.com/2020/04/httpclient-4-api-get-the-status-code-getstatusline-getstatuscode-example.html