在HttpClient API中獲取狀態代碼的快速指南。 getStatusLine（）。getStatusCode（）示例和相關的錯誤。

1.簡介

在這個非常快速的教程中，我將展示如何使用HttpClient 4獲取和驗證HTTP響應的StatusCode。

2. Maven依賴

要運行此HttiClient應用程序，需要以下jar。

commons-logging在內部被其他jar使用。 請不要忘記添加這些jar，否則會出現編譯時和運行時錯誤。

<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>

錯誤：

如果您錯過了commons-logging jar，則會產生以下異常。

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.從Http響應中檢索狀態代碼

發送HTTP請求后，經過處理后，響應將發送回調用方。

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); } } }

返回的響應類型為org.apache.http.HttpResponse ，它使我們能夠獲取請求的執行狀態。 getStatusLine（）方法返回保存請求狀態的StatusLine對象。 采用
getStatusCode（）僅獲取執行代碼。

輸出：

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

4. URL斷開時例外

如果給定的URL關閉或錯誤，則我們將獲得UnknownHostException運行時異常。

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.結論

在本文中，我們已經看到了如何獲取HttpClient請求的狀態代碼 。

和往常一樣，本文顯示的示例在Github上。

GitHub代碼

翻譯自: https://www.javacodegeeks.com/2020/04/httpclient-4-api-get-the-status-code-getstatusline-getstatuscode-example.html

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