Apache HttpClient 5.x中setRelativeRedirectsAllowed()替代方案咨询

1. HttpClient 5.x 中的替代方案 #

在 HttpClient 5.x 中，RequestConfig 类的 setRelativeRedirectsAllowed() 方法已被移除，因为默认重定向策略（DefaultRedirectStrategy）已经默认允许相对URL的重定向，无需单独配置该参数。

你可以直接简化原4.x的RequestConfig配置，移除setRelativeRedirectsAllowed(true)，5.x的默认行为就会对应原4.x开启该参数的效果。

5.x版本的基础配置示例：

final RequestConfig requestConfig = RequestConfig.custom()
        .setCookieSpec(CookieSpecs.STANDARD)
        .setConnectionRequestTimeout(...)
        .setConnectTimeout(...)
        .setRedirectsEnabled(true) // 仅需开启重定向即可，默认允许相对重定向
        .setSocketTimeout(...)
        .build();

final CloseableHttpClient client = HttpClients.custom() // 注意5.x中HttpClientBuilder改为HttpClients
        .setDefaultRequestConfig(requestConfig)
        .build();

final HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory(client);

2. 自定义控制相对重定向的实现 #

如果你的业务需要更精细的控制（比如仅在特定场景下允许/禁止相对重定向），可以通过自定义RedirectStrategy来实现：

步骤1：实现自定义RedirectStrategy #

import org.apache.hc.client5.http.impl.DefaultRedirectStrategy;
import org.apache.hc.client5.http.protocol.HttpClientContext;
import org.apache.hc.core5.http.HttpRequest;
import org.apache.hc.core5.http.HttpResponse;
import org.apache.hc.core5.http.ProtocolException;
import org.apache.hc.core5.net.URIBuilder;

import java.net.URI;
import java.net.URISyntaxException;

public class CustomRedirectStrategy extends DefaultRedirectStrategy {

    private final boolean allowRelativeRedirects;

    public CustomRedirectStrategy(boolean allowRelativeRedirects) {
        this.allowRelativeRedirects = allowRelativeRedirects;
    }

    @Override
    protected URI createLocationURI(final String location, final HttpRequest request, final HttpResponse response, final HttpClientContext context) throws ProtocolException {
        try {
            URI locationUri = new URI(location);
            // 判断是否为相对URI（无scheme和主机信息）
            if (!allowRelativeRedirects && !locationUri.isAbsolute()) {
                throw new ProtocolException("Relative redirects are not allowed: " + location);
            }
            // 如果是相对URI且允许，基于原请求URI构建绝对URI
            if (!locationUri.isAbsolute()) {
                URI originalUri = request.getUri();
                locationUri = new URIBuilder(originalUri)
                        .setPath(locationUri.getPath())
                        .setQuery(locationUri.getQuery())
                        .build();
            }
            return locationUri;
        } catch (URISyntaxException ex) {
            throw new ProtocolException("Invalid redirect URI: " + location, ex);
        }
    }
}

步骤2：将自定义策略配置到HttpClient #

final CloseableHttpClient client = HttpClients.custom()
        .setDefaultRequestConfig(requestConfig)
        .setRedirectStrategy(new CustomRedirectStrategy(true)) // 传入true允许，false禁止
        .build();

内容的提问来源于stack exchange，提问作者authorizeduser