HttpClient重定向处理示例

HttpClient自动处理所有类型的重定向，除了HTTP规范明确禁止的那些重定向需要用户干预。 请参阅其他(状态码303)在POST上重定向，并且按照HTTP规范的要求将PUT请求转换为GET请求。 可以使用自定义重定向策略来放宽由HTTP规范施加的对POST方法的自动重定向的限制。 在下面的教程中，我们将使用LaxRedirectStrategy来处理http重定向。

Maven依赖关系

我们使用maven来管理依赖关系，并使用Apache HttpClient 4.5版本。 将以下依赖项添加到您的项目中。

pom.xml 文件的内容如下 -

<?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>

重定向处理示例

在下面的例子中，我们对资源 http://httpbin.org/redirect/3 进行 HTTP GET。 此资源重新导向到另一个资源x次。可以使用URIUtils.resolve(httpGet.getURI(), target, redirectLocations)来获取最终的Http位置。

文件: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();
        }
    }
}

执行上面示例代码，得到以下结果 -

Executing request GET http://httpbin.org/redirect/3 HTTP/1.1
----------------------------------------
Final HTTP location: http://httpbin.org/get