httpclient实现digest认证

HttpClient可以通过提供的CredentialsProvider接口来实现digest认证。下面是一个示例代码：

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.impl.auth.DigestScheme;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class DigestAuthExample {

    public static void main(String[] args) throws IOException {
        String username = "user";
        String password = "password";
        HttpHost target = new HttpHost("localhost", 8080, "http");

        CredentialsProvider credsProvider = new BasicCredentialsProvider();
        credsProvider.setCredentials(
                new AuthScope(target.getHostName(), target.getPort()),
                new UsernamePasswordCredentials(username, password));

        CloseableHttpClient httpClient = HttpClients.custom()
                .setDefaultCredentialsProvider(credsProvider)
                .build();

        HttpClientContext context = HttpClientContext.create();
        HttpGet httpGet = new HttpGet("/");
        CloseableHttpResponse response = httpClient.execute(target, httpGet, context);
        try {
            HttpEntity entity = response.getEntity();
            EntityUtils.consume(entity);
        } finally {
            response.close();
        }

        // Get the digest scheme from the context
        DigestScheme digestScheme = (DigestScheme) context.getAuthScheme(target);

        // Use the digest scheme to generate the next request's headers
        HttpGet httpGet2 = new HttpGet("/");
        httpGet2.addHeader(digestScheme.authenticate(
                new UsernamePasswordCredentials(username, password),
                httpGet2, context));
        CloseableHttpResponse response2 = httpClient.execute(target, httpGet2, context);
        try {
            HttpEntity entity = response2.getEntity();
            EntityUtils.consume(entity);
        } finally {
            response2.close();
        }
    }
}

这个示例代码中，使用了BasicCredentialsProvider来提供用户名和密码。当httpClient执行第一次请求时，服务器返回401 Unauthorized响应，httpClient会尝试使用提供的凭据进行认证。然后，httpClient会使用DigestScheme生成下一个请求的摘要认证头。在第二次请求中，httpClient使用这个头来进行认证。