HttpClient自動處理所有型別的重定向,除了HTTP規範明確禁止的那些重定向需要使用者干預。 請參閱其他(狀態碼303
)在POST上重定向,並且按照HTTP規範的要求將PUT請求轉換為GET請求。 可以使用自定義重定向策略來放寬由HTTP規範施加的對POST方法的自動重定向的限制。 在下面的教學中,我們將使用LaxRedirectStrategy
來處理http重定向。
我們使用maven來管理依賴關係,並使用Apache HttpClient 4.5版本。 將以下依賴項新增到您的專案中。
pom.xml 檔案的內容如下 -
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.yiibai.httpclient.httmethods</groupId>
<artifactId>http-get</artifactId>
<version>1.0.0-SNAPSHOT</version>
<url>https://memorynotfound.com</url>
<name>httpclient - ${project.artifactId}</name>
<dependencies>
<!-- Apache Commons IO -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
在下面的例子中,我們對資源 http://httpbin.org/redirect/3 進行 HTTP GET。 此資源重新導向到另一個資源x
次。可以使用URIUtils.resolve(httpGet.getURI(), target, redirectLocations)
來獲取最終的Http位置。
檔案:HttpClientRedirectHandlingExample.java -
package com.yiibai.httpdemo;
import org.apache.http.HttpHost;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.client.utils.URIUtils;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.client.LaxRedirectStrategy;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.List;
/**
* This example demonstrates the use of {@link HttpGet} request method.
* and handling redirect strategy with {@link LaxRedirectStrategy}
*/
public class HttpClientRedirectHandlingExample {
public static void main(String... args) throws IOException, URISyntaxException {
CloseableHttpClient httpclient = HttpClients.custom()
.setRedirectStrategy(new LaxRedirectStrategy())
.build();
try {
HttpClientContext context = HttpClientContext.create();
HttpGet httpGet = new HttpGet("http://httpbin.org/redirect/3");
System.out.println("Executing request " + httpGet.getRequestLine());
System.out.println("----------------------------------------");
httpclient.execute(httpGet, context);
HttpHost target = context.getTargetHost();
List<URI> redirectLocations = context.getRedirectLocations();
URI location = URIUtils.resolve(httpGet.getURI(), target, redirectLocations);
System.out.println("Final HTTP location: " + location.toASCIIString());
} finally {
httpclient.close();
}
}
}
執行上面範例程式碼,得到以下結果 -
Executing request GET http://httpbin.org/redirect/3 HTTP/1.1
----------------------------------------
Final HTTP location: http://httpbin.org/get